diff --git a/docs-developer/CHANGELOG-formats.md b/docs-developer/CHANGELOG-formats.md
index d953a669bf..3d88bf1b8e 100644
--- a/docs-developer/CHANGELOG-formats.md
+++ b/docs-developer/CHANGELOG-formats.md
@@ -6,6 +6,28 @@ Note that this is not an exhaustive list. Processed profile format upgraders can
 
 ## Processed profile format
 
+### Version 75
+
+The func table (`profile.shared.funcTable`) representation changed, mirroring the v71 frame table change:
+
+- A new `flags` bitfield column was added. It can be stored as a plain array of numbers or as a `Uint8Array` (for profiles loaded from [JsonSlabs](https://github.com/mstange/json-slabs/) files). The bits are:
+  - `1 << 0` — `IsJS`: this func is a JavaScript function.
+  - `1 << 1` — `RelevantForJS`: this func should be treated as "relevant for JS" (e.g. DOM API label funcs).
+  - `1 << 2` — `HasResource`: `resource[i]` is meaningful.
+  - `1 << 3` — `HasSource`: `source[i]` is meaningful.
+  - `1 << 4` — `HasLine`: `lineNumber[i]` is meaningful.
+  - `1 << 5` — `HasColumn`: `columnNumber[i]` is meaningful.
+  - `1 << 6` — `HasOriginalLocation`: `originalLocation[i]` is meaningful.
+- The `isJS` and `relevantForJS` boolean columns were removed; the `IsJS` and `RelevantForJS` flag bits carry that information.
+- The `resource`, `source`, `lineNumber`, `columnNumber`, and `originalLocation` columns are no longer nullable in-band. Each may still be stored as a plain array, but the values are always numbers, and when the corresponding "Has..." flag is unset, the value in the column is ignored (producers typically write `0`).
+- The following columns can now optionally be stored as typed arrays:
+  - `name` (`Int32Array`)
+  - `resource` (`Int32Array`)
+  - `source` (`Int32Array`)
+  - `lineNumber` (`Int32Array`)
+  - `columnNumber` (`Int32Array`)
+  - `originalLocation` (`Int32Array`)
+
 ### Version 74
 
 The columns of the native symbol table (`profile.shared.nativeSymbols`) can now optionally be stored as typed arrays, for profiles loaded from [JsonSlabs](https://github.com/mstange/json-slabs/) files (.jslb, .jslb.gz). Regular JS / JSON arrays are still accepted.
diff --git a/src/actions/profile-view.ts b/src/actions/profile-view.ts
index 6ef3391213..a02aeb2c48 100644
--- a/src/actions/profile-view.ts
+++ b/src/actions/profile-view.ts
@@ -47,6 +47,7 @@ import {
   getTrackReferenceFromThreadIndex,
 } from 'firefox-profiler/profile-logic/tracks';
 
+import { FuncFlag } from 'firefox-profiler/types';
 import type {
   PreviewSelection,
   ImplementationFilter,
@@ -2096,11 +2097,14 @@ export function handleCallNodeTransformShortcut(
         break;
       case 'C': {
         const { funcTable } = unfilteredThread;
-        const resourceIndex = funcTable.resource[funcIndex];
+        if ((funcTable.flags[funcIndex] & FuncFlag.HasResource) === 0) {
+          // This func has no resource, so there is nothing to collapse.
+          return;
+        }
         dispatch(
           addCollapseResourceTransformToStack(
             threadsKey,
-            resourceIndex,
+            funcTable.resource[funcIndex],
             implementation
           )
         );
diff --git a/src/app-logic/constants.ts b/src/app-logic/constants.ts
index 14c3a1c395..6f9cae4e98 100644
--- a/src/app-logic/constants.ts
+++ b/src/app-logic/constants.ts
@@ -12,7 +12,7 @@ export const GECKO_PROFILE_VERSION = 36;
 // The current version of the "processed" profile format.
 // Please don't forget to update the processed profile format changelog in
 // `docs-developer/CHANGELOG-formats.md`.
-export const PROCESSED_PROFILE_VERSION = 74;
+export const PROCESSED_PROFILE_VERSION = 75;
 
 // The following are the margin sizes for the left and right of the timeline. Independent
 // components need to share these values.
diff --git a/src/app-logic/url-handling.ts b/src/app-logic/url-handling.ts
index 76475bf370..2e51d248b9 100644
--- a/src/app-logic/url-handling.ts
+++ b/src/app-logic/url-handling.ts
@@ -43,6 +43,7 @@ import type {
   MarkerIndex,
   SelectedMarkersPerThread,
 } from 'firefox-profiler/types';
+import { FuncFlag } from 'firefox-profiler/types';
 import {
   decodeUintArrayFromUrlComponent,
   encodeUintArrayForUrlComponent,
@@ -1719,7 +1720,7 @@ function getStackIndexFromVersion3JSCallNodePath(
     const prefix = offset === 0 ? null : stackIndex - offset;
     const frameIndex = stackTable.frame[stackIndex];
     const funcIndex = frameTable.func[frameIndex];
-    const isJS = funcTable.isJS[funcIndex];
+    const isJS = (funcTable.flags[funcIndex] & FuncFlag.IsJS) !== 0;
     // We know that at this point stack table is sorted and the following
     // condition holds:
     // assert(prefix === null || prefix < stackIndex);
@@ -1762,7 +1763,11 @@ function getVersion4JSCallNodePathFromStackIndex(
   while (nextStackIndex !== null) {
     const frameIndex: IndexIntoFrameTable = stackTable.frame[nextStackIndex];
     const funcIndex = frameTable.func[frameIndex];
-    if (funcTable.isJS[funcIndex] || funcTable.relevantForJS[funcIndex]) {
+    if (
+      (funcTable.flags[funcIndex] &
+        (FuncFlag.IsJS | FuncFlag.RelevantForJS)) !==
+      0
+    ) {
       callNodePath.unshift(funcIndex);
     }
     const offset: number = stackTable.prefixOffset[nextStackIndex];
diff --git a/src/components/shared/CallNodeContextMenu.tsx b/src/components/shared/CallNodeContextMenu.tsx
index cf7a9c391c..0603484fc4 100644
--- a/src/components/shared/CallNodeContextMenu.tsx
+++ b/src/components/shared/CallNodeContextMenu.tsx
@@ -56,6 +56,7 @@ import type {
   Page,
   SamplesLikeTable,
 } from 'firefox-profiler/types';
+import { FuncFlag } from 'firefox-profiler/types';
 
 import type { TabSlug } from 'firefox-profiler/app-logic/tabs-handling';
 import type { ConnectedProps } from 'firefox-profiler/utils/connect';
@@ -147,7 +148,7 @@ class CallNodeContextMenuImpl extends React.PureComponent<Props> {
     } = rightClickedCallNodeInfo;
 
     const funcIndex = callNodeInfo.funcForNode(callNodeIndex);
-    const isJS = funcTable.isJS[funcIndex];
+    const isJS = (funcTable.flags[funcIndex] & FuncFlag.IsJS) !== 0;
     const stringIndex = funcTable.name[funcIndex];
     const functionCall = stringTable.getString(stringIndex);
     const name = isJS ? functionCall : getFunctionName(functionCall);
@@ -184,10 +185,10 @@ class CallNodeContextMenuImpl extends React.PureComponent<Props> {
     } = rightClickedCallNodeInfo;
 
     const funcIndex = callNodeInfo.funcForNode(callNodeIndex);
-    const sourceIndex = funcTable.source[funcIndex];
-    if (sourceIndex === null) {
+    if ((funcTable.flags[funcIndex] & FuncFlag.HasSource) === 0) {
       return null;
     }
+    const sourceIndex = funcTable.source[funcIndex];
     const stringIndex = sources.filename[sourceIndex];
     return stringTable.getString(stringIndex);
   }
@@ -208,8 +209,15 @@ class CallNodeContextMenuImpl extends React.PureComponent<Props> {
     } = rightClickedCallNodeInfo;
 
     const funcIndex = callNodeInfo.funcForNode(callNodeIndex);
-    const line = funcTable.lineNumber[funcIndex];
-    const column = funcTable.columnNumber[funcIndex];
+    const funcFlags = funcTable.flags[funcIndex];
+    const line =
+      (funcFlags & FuncFlag.HasLine) !== 0
+        ? funcTable.lineNumber[funcIndex]
+        : null;
+    const column =
+      (funcFlags & FuncFlag.HasColumn) !== 0
+        ? funcTable.columnNumber[funcIndex]
+        : null;
     return { line, column };
   }
 
@@ -530,21 +538,22 @@ class CallNodeContextMenuImpl extends React.PureComponent<Props> {
     if (funcIndex === undefined) {
       return null;
     }
-    const isJS = funcTable.isJS[funcIndex];
+    const funcFlags = funcTable.flags[funcIndex];
+    const isJS = (funcFlags & FuncFlag.IsJS) !== 0;
 
     if (isJS) {
-      const sourceIndex = funcTable.source[funcIndex];
-      if (sourceIndex === null) {
+      if ((funcFlags & FuncFlag.HasSource) === 0) {
         return null;
       }
+      const sourceIndex = funcTable.source[funcIndex];
 
       const fileNameIndex = sources.filename[sourceIndex];
       return stringTable.getString(fileNameIndex);
     }
-    const resourceIndex = funcTable.resource[funcIndex];
-    if (resourceIndex === -1) {
+    if ((funcFlags & FuncFlag.HasResource) === 0) {
       return null;
     }
+    const resourceIndex = funcTable.resource[funcIndex];
     const resNameStringIndex = resourceTable.name[resourceIndex];
     return stringTable.getString(resNameStringIndex);
   }
@@ -608,7 +617,7 @@ class CallNodeContextMenuImpl extends React.PureComponent<Props> {
 
     const categoryIndex = callNodeInfo.categoryForNode(callNodeIndex);
     const funcIndex = callNodeInfo.funcForNode(callNodeIndex);
-    const isJS = funcTable.isJS[funcIndex];
+    const isJS = (funcTable.flags[funcIndex] & FuncFlag.IsJS) !== 0;
     const hasCategory = categoryIndex !== -1;
     // This could be the C++ library, or the JS filename.
     const nameForResource = this.getNameForSelectedResource();
diff --git a/src/components/tooltip/CallNode.tsx b/src/components/tooltip/CallNode.tsx
index 3319f8214a..4ebc6a65c3 100644
--- a/src/components/tooltip/CallNode.tsx
+++ b/src/components/tooltip/CallNode.tsx
@@ -27,6 +27,7 @@ import type {
   IndexIntoCategoryList,
   IndexIntoSubcategoryListForCategory,
 } from 'firefox-profiler/types';
+import { FuncFlag } from 'firefox-profiler/types';
 
 import type {
   TimingsForPath,
@@ -424,9 +425,10 @@ export class TooltipCallNode extends React.PureComponent<Props> {
     }
 
     let resource = null;
-    const resourceIndex = thread.funcTable.resource[funcIndex];
-
-    if (resourceIndex !== -1) {
+    const hasResource =
+      (thread.funcTable.flags[funcIndex] & FuncFlag.HasResource) !== 0;
+    if (hasResource) {
+      const resourceIndex = thread.funcTable.resource[funcIndex];
       const resourceNameIndex = thread.resourceTable.name[resourceIndex];
       // Because of our use of Grid Layout, all our elements need to be direct
       // children of the grid parent. That's why we use arrays here, to add
@@ -519,9 +521,10 @@ export class TooltipCallNode extends React.PureComponent<Props> {
         stackTypeLabel = 'JavaScript';
         break;
       case 'unsymbolicated':
-        stackTypeLabel = thread.funcTable.isJS[funcIndex]
-          ? 'Unsymbolicated native'
-          : 'Unsymbolicated or generated JIT instructions';
+        stackTypeLabel =
+          (thread.funcTable.flags[funcIndex] & FuncFlag.IsJS) !== 0
+            ? 'Unsymbolicated native'
+            : 'Unsymbolicated or generated JIT instructions';
         break;
       default:
         throw new Error(`Unknown stack type case "${stackType}".`);
diff --git a/src/node-tools/profiler-edit.ts b/src/node-tools/profiler-edit.ts
index 2dba4034d3..8cea8104d8 100644
--- a/src/node-tools/profiler-edit.ts
+++ b/src/node-tools/profiler-edit.ts
@@ -32,6 +32,7 @@ import {
   type WasmSymbolicationSpec,
 } from 'firefox-profiler/profile-logic/wasm-symbolication';
 import { getThreadsWithMarkersMatchingSearchFilter } from 'firefox-profiler/profile-logic/marker-data';
+import { FuncFlag } from 'firefox-profiler/types/profile';
 import type {
   Profile,
   RawThread,
@@ -124,8 +125,8 @@ export function collectFuncNames(profile: Profile): string[] {
   const result: string[] = [];
   for (let i = 0; i < funcTable.length; i++) {
     let name = stringArray[funcTable.name[i]];
-    const sourceIndex = funcTable.source[i];
-    if (sourceIndex !== null) {
+    if ((funcTable.flags[i] & FuncFlag.HasSource) !== 0) {
+      const sourceIndex = funcTable.source[i];
       const filename = stringArray[sources.filename[sourceIndex]];
       name += ` (${filename})`;
     }
diff --git a/src/profile-logic/call-tree.ts b/src/profile-logic/call-tree.ts
index 29189178db..c4a6360119 100644
--- a/src/profile-logic/call-tree.ts
+++ b/src/profile-logic/call-tree.ts
@@ -29,7 +29,7 @@ import type {
   SampleCategoriesAndSubcategories,
   IndexIntoCategoryList,
 } from 'firefox-profiler/types';
-import { ResourceType } from 'firefox-profiler/types';
+import { ResourceType, FuncFlag } from 'firefox-profiler/types';
 
 import ExtensionIcon from '../../res/img/svg/extension.svg';
 import { formatCallNodeNumber, formatPercent } from '../utils/format-numbers';
@@ -522,9 +522,14 @@ export class CallTree {
       const subcategoryIndex =
         this._callNodeInfo.subcategoryForNode(callNodeIndex);
       const badge = this._getInliningBadge(callNodeIndex, funcName);
-      const resourceIndex = this._thread.funcTable.resource[funcIndex];
-      const resourceType = this._thread.resourceTable.type[resourceIndex];
-      const isFrameLabel = resourceIndex === -1;
+      const funcFlags = this._thread.funcTable.flags[funcIndex];
+      const isFrameLabel = (funcFlags & FuncFlag.HasResource) === 0;
+      const resourceIndex = isFrameLabel
+        ? -1
+        : this._thread.funcTable.resource[funcIndex];
+      const resourceType = isFrameLabel
+        ? -1
+        : this._thread.resourceTable.type[resourceIndex];
       const libName = this._getOriginAnnotation(funcIndex);
       const weightType = this._weightType;
 
diff --git a/src/profile-logic/data-structures.ts b/src/profile-logic/data-structures.ts
index 257db159ea..944f171404 100644
--- a/src/profile-logic/data-structures.ts
+++ b/src/profile-logic/data-structures.ts
@@ -21,7 +21,7 @@ import type {
   RawJsAllocationsTable,
   RawUnbalancedNativeAllocationsTable,
   RawBalancedNativeAllocationsTable,
-  FuncTable,
+  RawFuncTable,
   RawMarkerTable,
   ResourceTable,
   RawNativeSymbolTable,
@@ -35,6 +35,8 @@ import type {
   IndexIntoFrameTable,
   IndexIntoFuncTable,
   IndexIntoLibs,
+  IndexIntoResourceTable,
+  IndexIntoSourceTable,
   IndexIntoStackTable,
   IndexIntoStringTable,
   IndexIntoCategoryList,
@@ -385,14 +387,24 @@ export function finishRawFrameTableBuilder(
   };
 }
 
-export function getEmptyFuncTable(): FuncTable {
+export type RawFuncTableBuilder = {
+  flags: number[];
+  name: IndexIntoStringTable[];
+  resource: IndexIntoResourceTable[];
+  source: IndexIntoSourceTable[];
+  lineNumber: number[];
+  columnNumber: number[];
+  originalLocation: IndexIntoSourceLocationTable[];
+  length: number;
+};
+
+export function getRawFuncTableBuilder(): RawFuncTableBuilder {
   return {
     // Important!
     // If modifying this structure, please update all callers of this function to ensure
     // that they are pushing on correctly to the data structure. These pushes may not
     // be caught by the type system.
-    isJS: [],
-    relevantForJS: [],
+    flags: [],
     name: [],
     resource: [],
     source: [],
@@ -403,24 +415,35 @@ export function getEmptyFuncTable(): FuncTable {
   };
 }
 
-export function shallowCloneFuncTable(funcTable: FuncTable): FuncTable {
+export function getRawFuncTableBuilderWithExistingContents(
+  funcTable: RawFuncTable
+): RawFuncTableBuilder {
   return {
     // Important!
     // If modifying this structure, please update all callers of this function to ensure
     // that they are pushing on correctly to the data structure. These pushes may not
     // be caught by the type system.
-    isJS: funcTable.isJS.slice(),
-    relevantForJS: funcTable.relevantForJS.slice(),
-    name: funcTable.name.slice(),
-    resource: funcTable.resource.slice(),
-    source: funcTable.source.slice(),
-    lineNumber: funcTable.lineNumber.slice(),
-    columnNumber: funcTable.columnNumber.slice(),
-    originalLocation: funcTable.originalLocation.slice(),
+    flags: Array.from(funcTable.flags),
+    name: Array.from(funcTable.name),
+    resource: Array.from(funcTable.resource),
+    source: Array.from(funcTable.source),
+    lineNumber: Array.from(funcTable.lineNumber),
+    columnNumber: Array.from(funcTable.columnNumber),
+    originalLocation: Array.from(funcTable.originalLocation),
     length: funcTable.length,
   };
 }
 
+export function finishRawFuncTableBuilder(
+  builder: RawFuncTableBuilder
+): RawFuncTable {
+  return { ...builder };
+}
+
+export function getEmptyRawFuncTable(): RawFuncTable {
+  return finishRawFuncTableBuilder(getRawFuncTableBuilder());
+}
+
 export function getEmptySourceLocationTable(): SourceLocationTable {
   return {
     source: [],
@@ -676,7 +699,7 @@ export function getEmptySharedData(): RawProfileSharedData {
   return {
     stackTable: finishRawStackTableBuilder(getRawStackTableBuilder()),
     frameTable: finishRawFrameTableBuilder(getRawFrameTableBuilder()),
-    funcTable: getEmptyFuncTable(),
+    funcTable: getEmptyRawFuncTable(),
     resourceTable: getEmptyResourceTable(),
     nativeSymbols: finishRawNativeSymbolTableBuilder(
       getRawNativeSymbolTableBuilder()
diff --git a/src/profile-logic/global-data-collector.ts b/src/profile-logic/global-data-collector.ts
index 894347eec7..461d7f8348 100644
--- a/src/profile-logic/global-data-collector.ts
+++ b/src/profile-logic/global-data-collector.ts
@@ -5,11 +5,12 @@
 import { StringTable } from '../utils/string-table';
 import {
   finishRawFrameTableBuilder,
+  finishRawFuncTableBuilder,
   finishRawNativeSymbolTableBuilder,
   finishRawStackTableBuilder,
   getRawFrameTableBuilder,
+  getRawFuncTableBuilder,
   getRawNativeSymbolTableBuilder,
-  getEmptyFuncTable,
   getEmptyResourceTable,
   getEmptySourceTable,
   getEmptySourceLocationTable,
@@ -24,7 +25,6 @@ import type {
   IndexIntoSourceTable,
   RawProfileSharedData,
   SourceTable,
-  FuncTable,
   ResourceTable,
   IndexIntoResourceTable,
   IndexIntoFuncTable,
@@ -33,9 +33,10 @@ import type {
   Address,
   Bytes,
 } from 'firefox-profiler/types';
-import { ResourceType } from 'firefox-profiler/types';
+import { ResourceType, FuncFlag } from 'firefox-profiler/types';
 import type {
   RawFrameTableBuilder,
+  RawFuncTableBuilder,
   RawNativeSymbolTableBuilder,
   RawStackTableBuilder,
 } from './data-structures';
@@ -56,7 +57,7 @@ export class GlobalDataCollector {
   _sources: SourceTable = getEmptySourceTable();
   _frameTable: RawFrameTableBuilder = getRawFrameTableBuilder();
   _stackTableBuilder: RawStackTableBuilder = getRawStackTableBuilder();
-  _funcTable: FuncTable = getEmptyFuncTable();
+  _funcTable: RawFuncTableBuilder = getRawFuncTableBuilder();
   _resourceTable: ResourceTable = getEmptyResourceTable();
   _nativeSymbols: RawNativeSymbolTableBuilder =
     getRawNativeSymbolTableBuilder();
@@ -105,15 +106,33 @@ export class GlobalDataCollector {
     const funcKey = `${name}-${isJS}-${relevantForJS}-${resource}-${source}-${lineNumber}-${columnNumber}`;
     let funcIndex = this._funcKeyToFuncIndex.get(funcKey);
     if (funcIndex === undefined) {
+      let flags = 0;
+      if (isJS) {
+        flags |= FuncFlag.IsJS;
+      }
+      if (relevantForJS) {
+        flags |= FuncFlag.RelevantForJS;
+      }
+      if (resource !== -1) {
+        flags |= FuncFlag.HasResource;
+      }
+      if (source !== null) {
+        flags |= FuncFlag.HasSource;
+      }
+      if (lineNumber !== null) {
+        flags |= FuncFlag.HasLine;
+      }
+      if (columnNumber !== null) {
+        flags |= FuncFlag.HasColumn;
+      }
       funcIndex = this._funcTable.length++;
+      this._funcTable.flags[funcIndex] = flags;
       this._funcTable.name[funcIndex] = name;
-      this._funcTable.isJS[funcIndex] = isJS;
-      this._funcTable.relevantForJS[funcIndex] = relevantForJS;
-      this._funcTable.resource[funcIndex] = resource;
-      this._funcTable.source[funcIndex] = source;
-      this._funcTable.lineNumber[funcIndex] = lineNumber;
-      this._funcTable.columnNumber[funcIndex] = columnNumber;
-      this._funcTable.originalLocation[funcIndex] = null;
+      this._funcTable.resource[funcIndex] = resource === -1 ? 0 : resource;
+      this._funcTable.source[funcIndex] = source ?? 0;
+      this._funcTable.lineNumber[funcIndex] = lineNumber ?? 0;
+      this._funcTable.columnNumber[funcIndex] = columnNumber ?? 0;
+      this._funcTable.originalLocation[funcIndex] = 0;
       this._funcKeyToFuncIndex.set(funcKey, funcIndex);
     }
     return funcIndex;
@@ -299,7 +318,7 @@ export class GlobalDataCollector {
     const shared: RawProfileSharedData = {
       stackTable: finishRawStackTableBuilder(this._stackTableBuilder),
       frameTable: finishRawFrameTableBuilder(this._frameTable),
-      funcTable: this._funcTable,
+      funcTable: finishRawFuncTableBuilder(this._funcTable),
       resourceTable: this._resourceTable,
       nativeSymbols: finishRawNativeSymbolTableBuilder(this._nativeSymbols),
       stringArray: this._stringArray,
diff --git a/src/profile-logic/import/simpleperf.ts b/src/profile-logic/import/simpleperf.ts
index b9d1a56b2c..d536f893ab 100644
--- a/src/profile-logic/import/simpleperf.ts
+++ b/src/profile-logic/import/simpleperf.ts
@@ -6,7 +6,7 @@ import type {
   CategoryList,
   CategoryColor,
   RawFrameTable,
-  FuncTable,
+  RawFuncTable,
   IndexIntoCategoryList,
   IndexIntoFrameTable,
   IndexIntoFuncTable,
@@ -19,9 +19,10 @@ import type {
   RawThread,
   RawStackTable,
 } from 'firefox-profiler/types/profile';
-import { FrameFlag } from 'firefox-profiler/types/profile';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types/profile';
 import {
-  getEmptyFuncTable,
+  getRawFuncTableBuilder,
+  finishRawFuncTableBuilder,
   getEmptyResourceTable,
   getRawFrameTableBuilder,
   getRawStackTableBuilder,
@@ -29,6 +30,7 @@ import {
   finishRawSamplesTableBuilder,
   finishRawStackTableBuilder,
   type RawFrameTableBuilder,
+  type RawFuncTableBuilder,
   type RawStackTableBuilder,
   getRawSamplesTableBuilder,
   type RawSamplesTableBuilder,
@@ -117,15 +119,15 @@ class FirefoxResourceTable {
 class FirefoxFuncTable {
   strings: StringTable;
 
-  funcTable: FuncTable = getEmptyFuncTable();
+  funcTable: RawFuncTableBuilder = getRawFuncTableBuilder();
   funcMap: Map<string, IndexIntoFuncTable> = new Map();
 
   constructor(strings: StringTable) {
     this.strings = strings;
   }
 
-  toJson(): FuncTable {
-    return this.funcTable;
+  toJson(): RawFuncTable {
+    return finishRawFuncTableBuilder(this.funcTable);
   }
 
   findOrAddFunc(name: string, resourceIndex: number): IndexIntoFuncTable {
@@ -135,14 +137,14 @@ class FirefoxFuncTable {
 
     let funcIndex = this.funcMap.get(mapKey);
     if (!funcIndex) {
+      // Non-JS, native function with an associated resource.
+      this.funcTable.flags.push(FuncFlag.HasResource);
       this.funcTable.name.push(nameIndex);
-      this.funcTable.isJS.push(false);
-      this.funcTable.relevantForJS.push(false);
       this.funcTable.resource.push(resourceIndex);
-      this.funcTable.source.push(null);
-      this.funcTable.lineNumber.push(null);
-      this.funcTable.columnNumber.push(null);
-      this.funcTable.originalLocation.push(null);
+      this.funcTable.source.push(0);
+      this.funcTable.lineNumber.push(0);
+      this.funcTable.columnNumber.push(0);
+      this.funcTable.originalLocation.push(0);
 
       funcIndex = this.funcTable.length++;
       this.funcMap.set(mapKey, funcIndex);
diff --git a/src/profile-logic/insert-stack-labels.ts b/src/profile-logic/insert-stack-labels.ts
index a0f30e4c09..038cd0b8bd 100644
--- a/src/profile-logic/insert-stack-labels.ts
+++ b/src/profile-logic/insert-stack-labels.ts
@@ -9,11 +9,12 @@ import type {
   Profile,
   Category,
 } from '../types/profile';
-import { FrameFlag } from '../types/profile';
+import { FrameFlag, FuncFlag } from '../types/profile';
 import {
   finishRawFrameTableBuilder,
+  finishRawFuncTableBuilder,
   getRawFrameTableBuilderWithExistingContents,
-  shallowCloneFuncTable,
+  getRawFuncTableBuilderWithExistingContents,
 } from 'firefox-profiler/profile-logic/data-structures';
 import { StringTable } from 'firefox-profiler/utils/string-table';
 import { updateRawThreadStacks } from 'firefox-profiler/profile-logic/profile-data';
@@ -108,7 +109,7 @@ export function insertStackLabels(
     stringArray,
   } = profile.shared;
   const frameTable = getRawFrameTableBuilderWithExistingContents(oldFrameTable);
-  const funcTable = shallowCloneFuncTable(oldFuncTable);
+  const funcTable = getRawFuncTableBuilderWithExistingContents(oldFuncTable);
   const stringTable = StringTable.withBackingArray(stringArray);
 
   const rootLabelName = 'Root (unaccounted / catch-all)';
@@ -124,14 +125,13 @@ export function insertStackLabels(
   for (let i = 0; i < allLabelNames.length; i++) {
     const labelName = allLabelNames[i];
     const funcIndex = funcTable.length++;
+    funcTable.flags[funcIndex] = FuncFlag.RelevantForJS;
     funcTable.name[funcIndex] = stringTable.indexForString(labelName);
-    funcTable.resource[funcIndex] = -1;
-    funcTable.source[funcIndex] = null;
-    funcTable.lineNumber[funcIndex] = null;
-    funcTable.columnNumber[funcIndex] = null;
-    funcTable.originalLocation[funcIndex] = null;
-    funcTable.isJS[funcIndex] = false;
-    funcTable.relevantForJS[funcIndex] = true;
+    funcTable.resource[funcIndex] = 0;
+    funcTable.source[funcIndex] = 0;
+    funcTable.lineNumber[funcIndex] = 0;
+    funcTable.columnNumber[funcIndex] = 0;
+    funcTable.originalLocation[funcIndex] = 0;
 
     const frameIndex = frameTable.length++;
     frameTable.flags[frameIndex] = FrameFlag.HasCategory;
@@ -154,8 +154,8 @@ export function insertStackLabels(
 
     // Include the filename (in brackets), if present. This allows matchers
     // like `onStateChange (chrome://browser/content/tabbrowser/`
-    const sourceIndex = funcTable.source[funcIndex];
-    if (sourceIndex !== null) {
+    if ((funcTable.flags[funcIndex] & FuncFlag.HasSource) !== 0) {
+      const sourceIndex = funcTable.source[funcIndex];
       const filenameString = stringArray[sources.filename[sourceIndex]];
       nameString += ` (${filenameString})`;
     }
@@ -215,8 +215,9 @@ export function insertStackLabels(
       inheritedLabelFrameIndexAtStack[stackIndex] = labelFrameIndex;
       stacksToInsertCount++;
     } else if (
-      funcTable.isJS[funcIndex] ||
-      funcTable.relevantForJS[funcIndex]
+      (funcTable.flags[funcIndex] &
+        (FuncFlag.IsJS | FuncFlag.RelevantForJS)) !==
+      0
     ) {
       labelFrameIndexToInsertAtStack[stackIndex] = null;
       inheritedLabelFrameIndexAtStack[stackIndex] = null;
@@ -281,7 +282,7 @@ export function insertStackLabels(
     ...profile.shared,
     stackTable,
     frameTable: finishRawFrameTableBuilder(frameTable),
-    funcTable,
+    funcTable: finishRawFuncTableBuilder(funcTable),
   };
   const newThreads = updateRawThreadStacks(profile.threads, (oldStack) =>
     oldStack !== null ? oldStackToNewStackPlusOne[oldStack] - 1 : null
diff --git a/src/profile-logic/js-tracer.ts b/src/profile-logic/js-tracer.ts
index b7f8aac500..b88b58b937 100644
--- a/src/profile-logic/js-tracer.ts
+++ b/src/profile-logic/js-tracer.ts
@@ -6,8 +6,10 @@ import {
   getRawMarkerTableBuilder,
   finishRawMarkerTableBuilder,
   finishRawFrameTableBuilder,
+  finishRawFuncTableBuilder,
   finishRawSamplesTableBuilder,
   finishRawStackTableBuilder,
+  getRawFuncTableBuilderWithExistingContents,
   getRawStackTableBuilderWithExistingContents,
   getRawFrameTableBuilderWithExistingContents,
   type RawSamplesTableBuilder,
@@ -27,7 +29,7 @@ import type {
   JsTracerTiming,
   Microseconds,
 } from 'firefox-profiler/types';
-import { FrameFlag } from 'firefox-profiler/types';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types';
 
 // See the function below for more information.
 type ScriptLocationToFuncIndex = Map<string, IndexIntoFuncTable | null>;
@@ -45,13 +47,16 @@ function getScriptLocationToFuncIndex({
 }: RawProfileSharedData): ScriptLocationToFuncIndex {
   const scriptLocationToFuncIndex: ScriptLocationToFuncIndex = new Map();
   for (let funcIndex = 0; funcIndex < funcTable.length; funcIndex++) {
-    if (!funcTable.isJS[funcIndex]) {
+    const funcFlags = funcTable.flags[funcIndex];
+    if ((funcFlags & FuncFlag.IsJS) === 0) {
       continue;
     }
-    const line = funcTable.lineNumber[funcIndex];
-    const column = funcTable.columnNumber[funcIndex];
-    const sourceIndex = funcTable.source[funcIndex];
-    if (column !== null && line !== null && sourceIndex !== null) {
+    const requiredFlags =
+      FuncFlag.HasLine | FuncFlag.HasColumn | FuncFlag.HasSource;
+    if ((funcFlags & requiredFlags) === requiredFlags) {
+      const line = funcTable.lineNumber[funcIndex];
+      const column = funcTable.columnNumber[funcIndex];
+      const sourceIndex = funcTable.source[funcIndex];
       const urlIndex = sources.filename[sourceIndex];
       const fileName = stringArray[urlIndex];
       const key = `${fileName}:${line}:${column}`;
@@ -520,7 +525,9 @@ export function convertJsTracerToThreadWithoutSamples(
     samples,
   };
 
-  const { funcTable } = shared;
+  const funcTable = getRawFuncTableBuilderWithExistingContents(
+    shared.funcTable
+  );
   const frameTable = getRawFrameTableBuilderWithExistingContents(
     shared.frameTable
   );
@@ -578,14 +585,13 @@ export function convertJsTracerToThreadWithoutSamples(
       if (generatedFuncIndex === undefined) {
         // Create a new function only if the event string is different.
         funcIndex = funcTable.length++;
+        funcTable.flags.push(FuncFlag.RelevantForJS);
         funcTable.name.push(eventStringIndex);
-        funcTable.isJS.push(false);
-        funcTable.resource.push(-1);
-        funcTable.relevantForJS.push(true);
-        funcTable.source.push(null);
-        funcTable.lineNumber.push(null);
-        funcTable.columnNumber.push(null);
-        funcTable.originalLocation.push(null);
+        funcTable.resource.push(0);
+        funcTable.source.push(0);
+        funcTable.lineNumber.push(0);
+        funcTable.columnNumber.push(0);
+        funcTable.originalLocation.push(0);
 
         funcMap.set(eventStringIndex, funcIndex);
       } else {
@@ -643,9 +649,10 @@ export function convertJsTracerToThreadWithoutSamples(
     unmatchedEventEnds[unmatchedIndex] = end;
   }
 
-  // Write the augmented stackTable and frameTable back to the shared data.
+  // Write the augmented stackTable, frameTable and funcTable back to the shared data.
   shared.stackTable = finishRawStackTableBuilder(stackTable);
   shared.frameTable = finishRawFrameTableBuilder(frameTable);
+  shared.funcTable = finishRawFuncTableBuilder(funcTable);
   thread.samples = finishRawSamplesTableBuilder(samples);
   thread.markers = finishRawMarkerTableBuilder(markers);
 
diff --git a/src/profile-logic/line-timings.ts b/src/profile-logic/line-timings.ts
index 175a9b8383..f792c3b38d 100644
--- a/src/profile-logic/line-timings.ts
+++ b/src/profile-logic/line-timings.ts
@@ -14,7 +14,7 @@ import type {
   IndexIntoLineSetTable,
   SourceLocationTable,
 } from 'firefox-profiler/types';
-import { FrameFlag } from 'firefox-profiler/types';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types';
 import { SetCollectionBuilder } from 'firefox-profiler/utils/set-collection';
 
 /**
@@ -68,21 +68,28 @@ export function getStackLineInfo(
     // column entirely, and defer the line lookup until we know the source
     // matches.
     const frameFlags = frameTable.flags[frame];
+    const funcFlags = funcTable.flags[func];
     const frameHasOriginalLocation =
       (frameFlags & FrameFlag.HasOriginalLocation) !== 0;
+    const funcHasOriginalLocation =
+      (funcFlags & FuncFlag.HasOriginalLocation) !== 0;
     const frameOriginalLocationIdx = frameHasOriginalLocation
       ? frameTable.originalLocation[frame]
       : -1;
-    const funcOriginalLocationIdx = funcTable.originalLocation[func];
+    const funcOriginalLocationIdx = funcHasOriginalLocation
+      ? funcTable.originalLocation[func]
+      : -1;
     let sourceIndexOfThisStack;
     if (frameHasOriginalLocation) {
       sourceIndexOfThisStack =
         sourceLocationTable.source[frameOriginalLocationIdx];
-    } else if (funcOriginalLocationIdx !== null) {
+    } else if (funcHasOriginalLocation) {
       sourceIndexOfThisStack =
         sourceLocationTable.source[funcOriginalLocationIdx];
-    } else {
+    } else if ((funcFlags & FuncFlag.HasSource) !== 0) {
       sourceIndexOfThisStack = funcTable.source[func];
+    } else {
+      sourceIndexOfThisStack = -1;
     }
 
     const matchesSource = sourceIndexOfThisStack === sourceViewSourceIndex;
@@ -93,11 +100,11 @@ export function getStackLineInfo(
       if (matchesSource) {
         if (frameHasOriginalLocation) {
           selfLineOrNull = sourceLocationTable.line[frameOriginalLocationIdx];
-        } else if (funcOriginalLocationIdx !== null) {
+        } else if (funcHasOriginalLocation) {
           selfLineOrNull = sourceLocationTable.line[funcOriginalLocationIdx];
         } else if ((frameFlags & FrameFlag.HasLine) !== 0) {
           selfLineOrNull = frameTable.line[frame];
-        } else {
+        } else if ((funcFlags & FuncFlag.HasLine) !== 0) {
           selfLineOrNull = funcTable.lineNumber[func];
         }
       }
@@ -224,19 +231,20 @@ export function getTotalLineTimingsForCallNode(
     // the per-sample object allocation.
     const funcIndex = frameTable.func[callNodeFrame];
     const frameFlags = frameTable.flags[callNodeFrame];
+    const funcFlags = funcTable.flags[funcIndex];
     let frameLine: number | null;
     if ((frameFlags & FrameFlag.HasOriginalLocation) !== 0) {
       frameLine =
         sourceLocationTable.line[frameTable.originalLocation[callNodeFrame]];
+    } else if ((funcFlags & FuncFlag.HasOriginalLocation) !== 0) {
+      frameLine =
+        sourceLocationTable.line[funcTable.originalLocation[funcIndex]];
+    } else if ((frameFlags & FrameFlag.HasLine) !== 0) {
+      frameLine = frameTable.line[callNodeFrame];
+    } else if ((funcFlags & FuncFlag.HasLine) !== 0) {
+      frameLine = funcTable.lineNumber[funcIndex];
     } else {
-      const funcOriginalLocationIdx = funcTable.originalLocation[funcIndex];
-      if (funcOriginalLocationIdx !== null) {
-        frameLine = sourceLocationTable.line[funcOriginalLocationIdx];
-      } else if ((frameFlags & FrameFlag.HasLine) !== 0) {
-        frameLine = frameTable.line[callNodeFrame];
-      } else {
-        frameLine = funcTable.lineNumber[funcIndex];
-      }
+      frameLine = null;
     }
     const line = frameLine !== null ? frameLine : funcLine;
     if (line === null) {
diff --git a/src/profile-logic/merge-compare.ts b/src/profile-logic/merge-compare.ts
index 3304cfcf13..a588e739e9 100644
--- a/src/profile-logic/merge-compare.ts
+++ b/src/profile-logic/merge-compare.ts
@@ -13,9 +13,10 @@ import {
   getRawNativeSymbolTableBuilder,
   finishRawNativeSymbolTableBuilder,
   finishRawFrameTableBuilder,
+  finishRawFuncTableBuilder,
   finishRawSamplesTableBuilder,
   getRawFrameTableBuilder,
-  getEmptyFuncTable,
+  getRawFuncTableBuilder,
   getRawStackTableBuilder,
   finishRawStackTableBuilder,
   getRawMarkerTableBuilder,
@@ -55,9 +56,9 @@ import type {
   IndexIntoStringTable,
   IndexIntoSourceTable,
   IndexIntoSourceLocationTable,
-  FuncTable,
   RawFrameTable,
   Lib,
+  RawFuncTable,
   RawNativeSymbolTable,
   ResourceTable,
   RawSamplesTable,
@@ -80,7 +81,7 @@ import type {
   ProfilerOverhead,
   ThreadIndex,
 } from 'firefox-profiler/types';
-import { FrameFlag } from 'firefox-profiler/types';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types';
 import { translateTransformStack } from './transforms';
 
 /**
@@ -763,22 +764,18 @@ function _mapNullableString(
     : null;
 }
 
-function _mapNullableSource(
-  sourceIndex: IndexIntoSourceTable | null,
+function _mapSource(
+  sourceIndex: IndexIntoSourceTable,
   oldSourceToNewSourcePlusOne: TranslationMapForSources
-): IndexIntoStringTable | null {
-  return sourceIndex !== null
-    ? oldSourceToNewSourcePlusOne[sourceIndex] - 1
-    : null;
+): IndexIntoSourceTable {
+  return oldSourceToNewSourcePlusOne[sourceIndex] - 1;
 }
 
-function _mapNullableOriginalLocation(
-  originalLocationIndex: IndexIntoSourceLocationTable | null,
-  oldOriginalLocationToNewPlusOne: TranslationMapForOriginalLocation
-): IndexIntoSourceLocationTable | null {
-  return originalLocationIndex !== null
-    ? oldOriginalLocationToNewPlusOne[originalLocationIndex] - 1
-    : null;
+function _mapResource(
+  resourceIndex: IndexIntoResourceTable,
+  oldResourceToNewResourcePlusOne: TranslationMapForResources
+): IndexIntoResourceTable {
+  return oldResourceToNewResourcePlusOne[resourceIndex] - 1;
 }
 
 function _mapOriginalLocation(
@@ -788,16 +785,6 @@ function _mapOriginalLocation(
   return oldOriginalLocationToNewPlusOne[originalLocationIndex] - 1;
 }
 
-function _mapFuncResource(
-  resourceIndex: IndexIntoResourceTable | -1,
-  oldResourceToNewResourcePlusOne: TranslationMapForResources
-): IndexIntoResourceTable | -1 {
-  if (resourceIndex === -1) {
-    return -1;
-  }
-  return oldResourceToNewResourcePlusOne[resourceIndex] - 1;
-}
-
 function _mapFunc(
   funcIndex: IndexIntoFuncTable,
   oldFuncToNewFuncPlusOne: TranslationMapForFuncs
@@ -953,10 +940,10 @@ function mergeFuncTables(
   translationMapsForSources: TranslationMapForSources[],
   translationMapsForOriginalLocation: TranslationMapForOriginalLocation[],
   translationMapsForStrings: TranslationMapForStrings[]
-): { funcTable: FuncTable; translationMaps: TranslationMapForFuncs[] } {
+): { funcTable: RawFuncTable; translationMaps: TranslationMapForFuncs[] } {
   const mapOfInsertedFuncs = new Map<string, IndexIntoFuncTable>();
   const translationMaps: TranslationMapForFuncs[] = [];
-  const newFuncTable = getEmptyFuncTable();
+  const newFuncTable = getRawFuncTableBuilder();
 
   profiles.forEach((profile, profileIndex) => {
     const { funcTable } = profile.shared;
@@ -969,14 +956,15 @@ function mergeFuncTables(
     const oldFuncToNewFuncPlusOne = new Int32Array(funcTable.length);
 
     for (let i = 0; i < funcTable.length; i++) {
-      const sourceIndex = _mapNullableSource(
-        funcTable.source[i],
-        oldSourceToNewSourcePlusOne
-      );
-      const resourceIndex = _mapFuncResource(
-        funcTable.resource[i],
-        oldResourceToNewResourcePlusOne
-      );
+      const flags = funcTable.flags[i];
+      const sourceIndex =
+        (flags & FuncFlag.HasSource) !== 0
+          ? _mapSource(funcTable.source[i], oldSourceToNewSourcePlusOne)
+          : 0;
+      const resourceIndex =
+        (flags & FuncFlag.HasResource) !== 0
+          ? _mapResource(funcTable.resource[i], oldResourceToNewResourcePlusOne)
+          : 0;
       const nameIndex = _mapString(
         funcTable.name[i],
         oldStringToNewStringPlusOne
@@ -991,7 +979,12 @@ function mergeFuncTables(
       //    number as well.
       // 3. Label frames: they have no resource, only a name. So we can't do
       //    better than this.
-      const funcKey = [nameIndex, resourceIndex, lineNumber].join('#');
+      const funcKey = [
+        nameIndex,
+        resourceIndex,
+        (flags & FuncFlag.HasResource) !== 0 ? 1 : 0,
+        (flags & FuncFlag.HasLine) !== 0 ? lineNumber : 'nil',
+      ].join('#');
       const insertedFuncIndex = mapOfInsertedFuncs.get(funcKey);
       if (insertedFuncIndex !== undefined) {
         oldFuncToNewFuncPlusOne[i] = insertedFuncIndex + 1;
@@ -1000,18 +993,19 @@ function mergeFuncTables(
       mapOfInsertedFuncs.set(funcKey, newFuncTable.length);
       oldFuncToNewFuncPlusOne[i] = newFuncTable.length + 1;
 
-      newFuncTable.isJS.push(funcTable.isJS[i]);
+      newFuncTable.flags.push(flags);
       newFuncTable.name.push(nameIndex);
       newFuncTable.resource.push(resourceIndex);
-      newFuncTable.relevantForJS.push(funcTable.relevantForJS[i]);
       newFuncTable.source.push(sourceIndex);
       newFuncTable.lineNumber.push(lineNumber);
       newFuncTable.columnNumber.push(funcTable.columnNumber[i]);
       newFuncTable.originalLocation.push(
-        _mapNullableOriginalLocation(
-          funcTable.originalLocation[i],
-          oldOriginalLocationToNewPlusOne
-        )
+        (flags & FuncFlag.HasOriginalLocation) !== 0
+          ? _mapOriginalLocation(
+              funcTable.originalLocation[i],
+              oldOriginalLocationToNewPlusOne
+            )
+          : 0
       );
 
       newFuncTable.length++;
@@ -1020,7 +1014,10 @@ function mergeFuncTables(
     translationMaps.push(oldFuncToNewFuncPlusOne);
   });
 
-  return { funcTable: newFuncTable, translationMaps };
+  return {
+    funcTable: finishRawFuncTableBuilder(newFuncTable),
+    translationMaps,
+  };
 }
 
 /**
diff --git a/src/profile-logic/process-profile.ts b/src/profile-logic/process-profile.ts
index 4ad47bdc35..b3ad6342d3 100644
--- a/src/profile-logic/process-profile.ts
+++ b/src/profile-logic/process-profile.ts
@@ -2161,7 +2161,7 @@ function convertSharedTablesEligibleColumns(
   shared: RawProfileSharedData,
   categories: CategoryList | undefined
 ): RawProfileSharedData {
-  const { stackTable, frameTable, nativeSymbols } = shared;
+  const { stackTable, frameTable, funcTable, nativeSymbols } = shared;
   return {
     ...shared,
     stackTable: {
@@ -2186,6 +2186,16 @@ function convertSharedTablesEligibleColumns(
       column: toInt32Array(frameTable.column),
       originalLocation: toInt32Array(frameTable.originalLocation),
     },
+    funcTable: {
+      length: funcTable.length,
+      flags: toUint8Array(funcTable.flags),
+      name: toInt32Array(funcTable.name),
+      resource: toInt32Array(funcTable.resource),
+      source: toInt32Array(funcTable.source),
+      lineNumber: toInt32Array(funcTable.lineNumber),
+      columnNumber: toInt32Array(funcTable.columnNumber),
+      originalLocation: toInt32Array(funcTable.originalLocation),
+    },
     nativeSymbols:
       computeNativeSymbolTableFromRawNativeSymbolTable(nativeSymbols),
   };
diff --git a/src/profile-logic/processed-profile-versioning.ts b/src/profile-logic/processed-profile-versioning.ts
index 3a1f1ff2a6..8fb6eda4e0 100644
--- a/src/profile-logic/processed-profile-versioning.ts
+++ b/src/profile-logic/processed-profile-versioning.ts
@@ -3510,6 +3510,85 @@ const _upgraders: {
       }
     }
   },
+  [75]: (profile: any) => {
+    // The func table representation changed, mirroring the v71 frame table
+    // change:
+    //  - A new `flags` bitfield column was added (Uint8Array or plain array).
+    //  - The `isJS` and `relevantForJS` boolean columns were removed; the
+    //    IsJS / RelevantForJS flag bits carry the same information.
+    //  - The `resource`, `source`, `lineNumber`, `columnNumber`, and
+    //    `originalLocation` columns are no longer nullable in-band. When the
+    //    corresponding "Has..." flag is not set, the value in the column is
+    //    ignored and can be any placeholder (we write 0).
+    //  - All columns may now optionally be stored as typed arrays
+    //    (Int32Array for the non-flags columns).
+
+    // A snapshot of the `FuncFlag` enum as of version 75. Don't refer to the
+    // current `FuncFlag` enum here; upgraders must keep working even if later
+    // versions renumber or remove flags.
+    const IsJS = 1 << 0;
+    const RelevantForJS = 1 << 1;
+    const HasResource = 1 << 2;
+    const HasSource = 1 << 3;
+    const HasLine = 1 << 4;
+    const HasColumn = 1 << 5;
+    const HasOriginalLocation = 1 << 6;
+
+    const { funcTable } = profile.shared;
+    const {
+      isJS,
+      relevantForJS,
+      resource,
+      source,
+      lineNumber,
+      columnNumber,
+      originalLocation,
+      length,
+    } = funcTable;
+    const flags = new Array<number>(length);
+    for (let i = 0; i < length; i++) {
+      let f = 0;
+      if (isJS[i]) {
+        f |= IsJS;
+      }
+      if (relevantForJS[i]) {
+        f |= RelevantForJS;
+      }
+      if (
+        resource[i] !== -1 &&
+        resource[i] !== null &&
+        resource[i] !== undefined
+      ) {
+        f |= HasResource;
+      } else {
+        resource[i] = 0;
+      }
+      if (source[i] !== null && source[i] !== undefined) {
+        f |= HasSource;
+      } else {
+        source[i] = 0;
+      }
+      if (lineNumber[i] !== null && lineNumber[i] !== undefined) {
+        f |= HasLine;
+      } else {
+        lineNumber[i] = 0;
+      }
+      if (columnNumber[i] !== null && columnNumber[i] !== undefined) {
+        f |= HasColumn;
+      } else {
+        columnNumber[i] = 0;
+      }
+      if (originalLocation[i] !== null && originalLocation[i] !== undefined) {
+        f |= HasOriginalLocation;
+      } else {
+        originalLocation[i] = 0;
+      }
+      flags[i] = f;
+    }
+    funcTable.flags = flags;
+    delete funcTable.isJS;
+    delete funcTable.relevantForJS;
+  },
   // If you add a new upgrader here, please document the change in
   // `docs-developer/CHANGELOG-formats.md`.
 };
diff --git a/src/profile-logic/profile-compacting.ts b/src/profile-logic/profile-compacting.ts
index d232638fd1..43e647073e 100644
--- a/src/profile-logic/profile-compacting.ts
+++ b/src/profile-logic/profile-compacting.ts
@@ -14,14 +14,14 @@ import type {
   IndexIntoStackTable,
   RawStackTable,
   RawFrameTable,
-  FuncTable,
+  RawFuncTable,
   ResourceTable,
   RawNativeSymbolTable,
   Lib,
   SourceTable,
   SourceLocationTable,
 } from 'firefox-profiler/types';
-import { FrameFlag } from 'firefox-profiler/types';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types';
 import {
   assertExhaustiveCheck,
   ensureExists,
@@ -79,10 +79,6 @@ type ColumnDescription<TCol> =
             | { type: 'NO_REF' }
         :
             | { type: 'INDEX_REF'; referencedTable: TableCompactionState }
-            | {
-                type: 'INDEX_REF_OR_NEG_ONE';
-                referencedTable: TableCompactionState;
-              }
             | { type: 'NO_REF' });
 
 type TableDescription<T> = {
@@ -120,10 +116,6 @@ const ColDesc = {
     type: 'INDEX_REF_OR_NULL' as const,
     referencedTable,
   }),
-  indexRefOrNegOne: (referencedTable: TableCompactionState) => ({
-    type: 'INDEX_REF_OR_NEG_ONE' as const,
-    referencedTable,
-  }),
   selfPrefixOffset: () => ({ type: 'SELF_RELATIVE_PARENT' as const }),
   noRef: () => ({ type: 'NO_REF' as const }),
   // Like noRef, but the compacted column is always a typed array of the given
@@ -231,15 +223,20 @@ export function computeCompactedProfile(
       FrameFlag.HasOriginalLocation
     ),
   };
-  const funcTableDesc: TableDescription<FuncTable> = {
-    name: ColDesc.indexRef(tcs.stringArray),
-    isJS: ColDesc.noRef(),
-    relevantForJS: ColDesc.noRef(),
-    resource: ColDesc.indexRefOrNegOne(tcs.resourceTable),
-    source: ColDesc.indexRefOrNull(tcs.sources),
+  const funcTableDesc: TableDescription<RawFuncTable> = {
+    flags: ColDesc.noRef(),
+    name: ColDesc.indexRefInt32(tcs.stringArray),
+    resource: ColDesc.indexRefInt32GatedByFlag(
+      tcs.resourceTable,
+      FuncFlag.HasResource
+    ),
+    source: ColDesc.indexRefInt32GatedByFlag(tcs.sources, FuncFlag.HasSource),
     lineNumber: ColDesc.noRef(),
     columnNumber: ColDesc.noRef(),
-    originalLocation: ColDesc.indexRefOrNull(tcs.sourceLocationTable),
+    originalLocation: ColDesc.indexRefInt32GatedByFlag(
+      tcs.sourceLocationTable,
+      FuncFlag.HasOriginalLocation
+    ),
   };
   const sourceLocationTableDesc: TableDescription<SourceLocationTable> = {
     source: ColDesc.indexRef(tcs.sources),
@@ -417,13 +414,6 @@ function _markTableAndComputeTranslation<T>(
         break;
       case 'SELF_RELATIVE_PARENT':
         break; // already handled in the first pass
-      case 'INDEX_REF_OR_NEG_ONE':
-        markColumnWithNegOneableFields(
-          col,
-          markBuffer,
-          desc.referencedTable.markBuffer
-        );
-        break;
       case 'NO_REF':
       case 'NO_REF_TYPED':
         break;
@@ -482,21 +472,6 @@ function markSelfColumnPrefixOffset(
   }
 }
 
-function markColumnWithNegOneableFields(
-  col: Array<number | -1>,
-  shouldMark: BitSet,
-  markBuf: BitSet
-) {
-  for (let i = 0; i < col.length; i++) {
-    if (checkBit(shouldMark, i)) {
-      const val = col[i];
-      if (val !== -1) {
-        setBit(markBuf, val);
-      }
-    }
-  }
-}
-
 function markColumnGatedByFlag(
   col: Array<number> | Int32Array<ArrayBuffer>,
   flagCol: Array<number> | Uint8Array<ArrayBuffer>,
@@ -634,14 +609,6 @@ function _compactTable<T extends { length: number }>(
           newLength
         );
         break;
-      case 'INDEX_REF_OR_NEG_ONE':
-        result[key] = _compactColIndexOrNegOne(
-          oldCol,
-          markBuffer,
-          desc.referencedTable.oldIndexToNewIndexPlusOne,
-          newLength
-        );
-        break;
       case 'NO_REF':
         result[key] = _compactColCopy(oldCol, markBuffer, newLength);
         break;
@@ -762,23 +729,6 @@ function _compactColIndexOrNull(
   return newCol;
 }
 
-function _compactColIndexOrNegOne(
-  oldCol: (number | -1)[],
-  markBuffer: BitSet,
-  oldIndexToNewIndexPlusOne: Int32Array,
-  newLength: number
-): (number | -1)[] {
-  const newCol: (number | -1)[] = new Array(newLength);
-  let newIndex = 0;
-  for (let i = 0; i < oldCol.length; i++) {
-    if (checkBit(markBuffer, i)) {
-      const val = oldCol[i];
-      newCol[newIndex++] = val !== -1 ? oldIndexToNewIndexPlusOne[val] - 1 : -1;
-    }
-  }
-  return newCol;
-}
-
 function _compactColSelfPrefixOffset(
   oldCol: Int32Array<ArrayBuffer>,
   markBuffer: BitSet,
diff --git a/src/profile-logic/profile-data.ts b/src/profile-logic/profile-data.ts
index b9c829fe7d..6ed16f8483 100644
--- a/src/profile-logic/profile-data.ts
+++ b/src/profile-logic/profile-data.ts
@@ -11,7 +11,6 @@ import {
   finishRawStackTableBuilder,
   getEmptyCallNodeTable,
   getRawFrameTableBuilderWithExistingContents,
-  shallowCloneFuncTable,
 } from './data-structures';
 import {
   CallNodeInfoNonInverted,
@@ -58,6 +57,7 @@ import type {
   RawFrameTable,
   FrameTable,
   FuncTable,
+  RawFuncTable,
   NativeSymbolTable,
   RawNativeSymbolTable,
   ResourceTable,
@@ -110,7 +110,12 @@ import type {
   SampleCategoriesAndSubcategories,
   SourceLocationTable,
 } from 'firefox-profiler/types';
-import { SelectedState, ResourceType, FrameFlag } from 'firefox-profiler/types';
+import {
+  SelectedState,
+  ResourceType,
+  FrameFlag,
+  FuncFlag,
+} from 'firefox-profiler/types';
 import type { CallNodeInfo, SuffixOrderIndex } from './call-node-info';
 import {
   toFloat64Array,
@@ -1781,8 +1786,9 @@ export function computeTransformOutputForImplementationFilter(
         stackTable,
         frameTable,
         (funcIndex) => {
+          const funcFlags = funcTable.flags[funcIndex];
           // Return quickly if this is a JS frame.
-          if (funcTable.isJS[funcIndex]) {
+          if ((funcFlags & FuncFlag.IsJS) !== 0) {
             return false;
           }
           // Regular C++ functions are associated with a resource that describes the
@@ -1793,7 +1799,7 @@ export function computeTransformOutputForImplementationFilter(
             funcTable.name[funcIndex]
           );
           const isProbablyJitCode =
-            funcTable.resource[funcIndex] === -1 &&
+            (funcFlags & FuncFlag.HasResource) === 0 &&
             locationString.startsWith('0x');
           return !isProbablyJitCode;
         }
@@ -1804,7 +1810,9 @@ export function computeTransformOutputForImplementationFilter(
         frameTable,
         (funcIndex) => {
           return (
-            funcTable.isJS[funcIndex] || funcTable.relevantForJS[funcIndex]
+            (funcTable.flags[funcIndex] &
+              (FuncFlag.IsJS | FuncFlag.RelevantForJS)) !==
+            0
           );
         }
       );
@@ -2028,8 +2036,9 @@ export function computeFuncMatchesSearchString(
       return true;
     }
 
-    const sourceIndex = funcTable.source[func];
-    if (sourceIndex !== null) {
+    const funcFlags = funcTable.flags[func];
+    if ((funcFlags & FuncFlag.HasSource) !== 0) {
+      const sourceIndex = funcTable.source[func];
       const urlIndex = sources.filename[sourceIndex];
       const fileNameString = stringTable.getString(urlIndex);
       if (fileNameString.toLowerCase().includes(lowercaseSearchString)) {
@@ -2037,8 +2046,8 @@ export function computeFuncMatchesSearchString(
       }
     }
 
-    const resourceIndex = funcTable.resource[func];
-    if (resourceIndex !== -1) {
+    if ((funcFlags & FuncFlag.HasResource) !== 0) {
+      const resourceIndex = funcTable.resource[func];
       const resourceNameIndex = resourceTable.name[resourceIndex];
       const resourceNameString = stringTable.getString(resourceNameIndex);
       if (resourceNameString.toLowerCase().includes(lowercaseSearchString)) {
@@ -3609,36 +3618,49 @@ export function getOriginalPositionForFrame(
     };
   }
 
-  if (sourceLocationTable !== null) {
+  const funcFlags = funcTable.flags[funcIndex];
+  if (
+    sourceLocationTable !== null &&
+    (funcFlags & FuncFlag.HasOriginalLocation) !== 0
+  ) {
     const funcOriginalLocationIdx = funcTable.originalLocation[funcIndex];
-    if (funcOriginalLocationIdx !== null) {
-      return {
-        source: sourceLocationTable.source[funcOriginalLocationIdx],
-        line: sourceLocationTable.line[funcOriginalLocationIdx],
-        column: sourceLocationTable.column[funcOriginalLocationIdx],
-      };
-    }
+    return {
+      source: sourceLocationTable.source[funcOriginalLocationIdx],
+      line: sourceLocationTable.line[funcOriginalLocationIdx],
+      column: sourceLocationTable.column[funcOriginalLocationIdx],
+    };
   }
 
+  const funcSource =
+    (funcFlags & FuncFlag.HasSource) !== 0 ? funcTable.source[funcIndex] : null;
+  const funcLine =
+    (funcFlags & FuncFlag.HasLine) !== 0
+      ? funcTable.lineNumber[funcIndex]
+      : null;
+  const funcColumn =
+    (funcFlags & FuncFlag.HasColumn) !== 0
+      ? funcTable.columnNumber[funcIndex]
+      : null;
+
   if (frameIndex !== null) {
     const frameFlags = frameTable.flags[frameIndex];
     return {
-      source: funcTable.source[funcIndex],
+      source: funcSource,
       line:
         (frameFlags & FrameFlag.HasLine) !== 0
           ? frameTable.line[frameIndex]
-          : funcTable.lineNumber[funcIndex],
+          : funcLine,
       column:
         (frameFlags & FrameFlag.HasColumn) !== 0
           ? frameTable.column[frameIndex]
-          : funcTable.columnNumber[funcIndex],
+          : funcColumn,
     };
   }
 
   return {
-    source: funcTable.source[funcIndex],
-    line: funcTable.lineNumber[funcIndex],
-    column: funcTable.columnNumber[funcIndex],
+    source: funcSource,
+    line: funcLine,
+    column: funcColumn,
   };
 }
 
@@ -3659,8 +3681,8 @@ export function getOriginAnnotationForFunc(
 ): string {
   let resourceType = null;
   let origin = null;
-  const resourceIndex = funcTable.resource[funcIndex];
-  if (resourceIndex !== -1) {
+  if ((funcTable.flags[funcIndex] & FuncFlag.HasResource) !== 0) {
+    const resourceIndex = funcTable.resource[funcIndex];
     resourceType = resourceTable.type[resourceIndex];
     const resourceNameIndex = resourceTable.name[resourceIndex];
     origin = stringTable.getString(resourceNameIndex);
@@ -3726,10 +3748,41 @@ export function getOriginAnnotationForFunc(
  * These are used by the "collapse resource" transform.
  */
 export function reserveFunctionsForCollapsedResources(
-  originalFuncTable: FuncTable,
+  originalFuncTable: RawFuncTable,
   resourceTable: ResourceTable
 ): FuncTableWithReservedFunctions {
-  const funcTable = shallowCloneFuncTable(originalFuncTable);
+  // We reserve exactly one func per resource, so we know the final length up
+  // front. Allocate the derived columns at that length and copy the original
+  // contents into them, instead of going through a RawFuncTableBuilder; the
+  // latter would copy the entire funcTable twice, once into plain arrays and
+  // once back into typed arrays.
+  const originalLength = originalFuncTable.length;
+  const length = originalLength + resourceTable.length;
+  const flags = new Uint8Array(length);
+  const name = new Int32Array(length);
+  const resource = new Int32Array(length);
+  const source = new Int32Array(length);
+  const lineNumber = new Int32Array(length);
+  const columnNumber = new Int32Array(length);
+  const originalLocation = new Int32Array(length);
+  flags.set(originalFuncTable.flags);
+  name.set(originalFuncTable.name);
+  resource.set(originalFuncTable.resource);
+  source.set(originalFuncTable.source);
+  lineNumber.set(originalFuncTable.lineNumber);
+  columnNumber.set(originalFuncTable.columnNumber);
+  originalLocation.set(originalFuncTable.originalLocation);
+  const funcTable = {
+    flags,
+    name,
+    resource,
+    source,
+    lineNumber,
+    columnNumber,
+    originalLocation,
+    length,
+  };
+
   const reservedFunctionsForResources = new Map<
     IndexIntoResourceTable,
     IndexIntoFuncTable
@@ -3746,24 +3799,19 @@ export function reserveFunctionsForCollapsedResources(
     resourceIndex++
   ) {
     const resourceType = resourceTable.type[resourceIndex];
-    const name = resourceTable.name[resourceIndex];
     const isJS = jsResourceTypes.includes(resourceType);
-    const funcIndex = funcTable.length;
-    funcTable.isJS.push(isJS);
-    funcTable.relevantForJS.push(isJS);
-    funcTable.name.push(name);
-    funcTable.resource.push(resourceIndex);
-    funcTable.source.push(null);
-    funcTable.lineNumber.push(null);
-    funcTable.columnNumber.push(null);
-    funcTable.originalLocation.push(null);
-    funcTable.length++;
+    const funcIndex = originalLength + resourceIndex;
+    // The source, lineNumber, columnNumber and originalLocation columns keep
+    // the zero they were allocated with; the corresponding flags are unset, so
+    // those values are ignored.
+    flags[funcIndex] = isJS
+      ? FuncFlag.HasResource | FuncFlag.IsJS | FuncFlag.RelevantForJS
+      : FuncFlag.HasResource;
+    name[funcIndex] = resourceTable.name[resourceIndex];
+    resource[funcIndex] = resourceIndex;
     reservedFunctionsForResources.set(resourceIndex, funcIndex);
   }
-  return {
-    funcTable,
-    reservedFunctionsForResources,
-  };
+  return { funcTable, reservedFunctionsForResources };
 }
 
 /**
@@ -4597,7 +4645,20 @@ export function findAddressProofForFile(
 ): AddressProof | null {
   const { libs } = profile;
   const { frameTable, funcTable } = profile.shared;
-  const func = funcTable.source.indexOf(sourceIndex);
+  // Scan for the func manually rather than using `funcTable.source.indexOf`:
+  // the `source` column only carries a meaningful value for funcs which have
+  // the `HasSource` flag set, and holds an arbitrary value (usually zero) for
+  // all other funcs. An `indexOf` would happily match one of those.
+  let func = -1;
+  for (let i = 0; i < funcTable.length; i++) {
+    if (
+      (funcTable.flags[i] & FuncFlag.HasSource) !== 0 &&
+      funcTable.source[i] === sourceIndex
+    ) {
+      func = i;
+      break;
+    }
+  }
   if (func === -1) {
     return null;
   }
@@ -4947,6 +5008,19 @@ export function computeNativeSymbolTableFromRawNativeSymbolTable(
   };
 }
 
+export function computeFuncTableFromRawFuncTable(raw: RawFuncTable): FuncTable {
+  return {
+    flags: toUint8Array(raw.flags),
+    name: toInt32Array(raw.name),
+    resource: toInt32Array(raw.resource),
+    source: toInt32Array(raw.source),
+    lineNumber: toInt32Array(raw.lineNumber),
+    columnNumber: toInt32Array(raw.columnNumber),
+    originalLocation: toInt32Array(raw.originalLocation),
+    length: raw.length,
+  };
+}
+
 export function computeStackTableFromRawStackTable(
   rawStackTable: RawStackTable,
   frameTable: FrameTable,
diff --git a/src/profile-logic/sanitize.ts b/src/profile-logic/sanitize.ts
index d7d04dd472..5b0adeb2bc 100644
--- a/src/profile-logic/sanitize.ts
+++ b/src/profile-logic/sanitize.ts
@@ -6,7 +6,8 @@ import {
   getEmptyExtensions,
   getRawMarkerTableBuilderFromExisting,
   finishRawMarkerTableBuilder,
-  shallowCloneFuncTable,
+  getRawFuncTableBuilderWithExistingContents,
+  finishRawFuncTableBuilder,
 } from './data-structures';
 import { computeCompactedProfile } from './profile-compacting';
 import { StringTable } from '../utils/string-table';
@@ -37,7 +38,7 @@ import type {
   IndexIntoResourceTable,
   ProfileIndexTranslationMaps,
 } from 'firefox-profiler/types';
-import { FrameFlag } from 'firefox-profiler/types';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types';
 
 export type SanitizeProfileResult = {
   readonly profile: Profile;
@@ -186,8 +187,8 @@ export function sanitizePII(
     if (sanitizedFuncIndexesToFrameIndex.size) {
       const resourcesToBeSanitized = new Set<IndexIntoResourceTable>();
 
-      const newFuncTable = (newShared.funcTable =
-        shallowCloneFuncTable(funcTable));
+      const newFuncTable =
+        getRawFuncTableBuilderWithExistingContents(funcTable);
       const newFrameTable = (newShared.frameTable = {
         ...frameTable,
         flags: Array.from(frameTable.flags),
@@ -208,13 +209,16 @@ export function sanitizePII(
           const name = stringTable.indexForString(
             `<Func #${sanitizedFuncIndex}>`
           );
+          // Preserve IsJS/RelevantForJS from the original; strip everything else.
+          const oldFlags = funcTable.flags[funcIndex];
+          const preservedMask = FuncFlag.IsJS | FuncFlag.RelevantForJS;
+          newFuncTable.flags.push(oldFlags & preservedMask);
           newFuncTable.name.push(name);
-          newFuncTable.isJS.push(funcTable.isJS[funcIndex]);
-          newFuncTable.relevantForJS.push(funcTable.isJS[funcIndex]);
-          newFuncTable.resource.push(-1);
-          newFuncTable.source.push(null);
-          newFuncTable.lineNumber.push(null);
-          newFuncTable.columnNumber.push(null);
+          newFuncTable.resource.push(0);
+          newFuncTable.source.push(0);
+          newFuncTable.lineNumber.push(0);
+          newFuncTable.columnNumber.push(0);
+          newFuncTable.originalLocation.push(0);
           newFuncTable.length++;
 
           frameIndexes.forEach(
@@ -227,13 +231,22 @@ export function sanitizePII(
           const name = stringTable.indexForString(`<Func #${funcIndex}>`);
           newFuncTable.name[funcIndex] = name;
 
-          newFuncTable.source[funcIndex] = null;
-          if (newFuncTable.resource[funcIndex] >= 0) {
+          const clearMask = ~(
+            FuncFlag.HasResource |
+            FuncFlag.HasSource |
+            FuncFlag.HasLine |
+            FuncFlag.HasColumn |
+            FuncFlag.HasOriginalLocation
+          );
+          if ((newFuncTable.flags[funcIndex] & FuncFlag.HasResource) !== 0) {
             resourcesToBeSanitized.add(newFuncTable.resource[funcIndex]);
           }
-          newFuncTable.resource[funcIndex] = -1;
-          newFuncTable.lineNumber[funcIndex] = null;
-          newFuncTable.columnNumber[funcIndex] = null;
+          newFuncTable.flags[funcIndex] &= clearMask;
+          newFuncTable.resource[funcIndex] = 0;
+          newFuncTable.source[funcIndex] = 0;
+          newFuncTable.lineNumber[funcIndex] = 0;
+          newFuncTable.columnNumber[funcIndex] = 0;
+          newFuncTable.originalLocation[funcIndex] = 0;
         }
 
         // In both cases, nullify some information in all frames.
@@ -253,9 +266,12 @@ export function sanitizePII(
           name: resourceTable.name.slice(),
           host: resourceTable.host.slice(),
         });
-        const remainingResources = new Set<IndexIntoResourceTable>(
-          newFuncTable.resource
-        );
+        const remainingResources = new Set<IndexIntoResourceTable>();
+        for (let i = 0; i < newFuncTable.length; i++) {
+          if ((newFuncTable.flags[i] & FuncFlag.HasResource) !== 0) {
+            remainingResources.add(newFuncTable.resource[i]);
+          }
+        }
         for (const resourceIndex of resourcesToBeSanitized) {
           if (!remainingResources.has(resourceIndex)) {
             // This resource was used only by sanitized functions. Sanitize it
@@ -268,6 +284,8 @@ export function sanitizePII(
           }
         }
       }
+
+      newShared.funcTable = finishRawFuncTableBuilder(newFuncTable);
     }
 
     // First we'll loop the stack table and populate a typed array with a value
diff --git a/src/profile-logic/source-map-symbolication.ts b/src/profile-logic/source-map-symbolication.ts
index 3d899b562b..677640726c 100644
--- a/src/profile-logic/source-map-symbolication.ts
+++ b/src/profile-logic/source-map-symbolication.ts
@@ -68,8 +68,9 @@
 
 import {
   finishRawFrameTableBuilder,
-  shallowCloneFuncTable,
+  finishRawFuncTableBuilder,
   getRawFrameTableBuilderWithExistingContents,
+  getRawFuncTableBuilderWithExistingContents,
   shallowCloneSourceLocationTable,
 } from './data-structures';
 import { StringTable } from '../utils/string-table';
@@ -91,14 +92,14 @@ import type { FunctionScope } from './source-map-scope-tree';
 import type {
   IndexIntoSourceTable,
   IndexIntoFuncTable,
+  RawFuncTable,
   IndexIntoFrameTable,
-  FuncTable,
   RawFrameTable,
   RawProfileSharedData,
   SourceLocationTable,
   SourceTable,
 } from '../types';
-import { FrameFlag } from '../types';
+import { FrameFlag, FuncFlag } from '../types';
 import type { NullableMappedPosition } from 'source-map';
 import type { SourceMapConsumer } from './source-map-store';
 import type {
@@ -135,7 +136,7 @@ type ParsedSource = {
 // tables from the current shared state at apply time.
 export type SourceMapSymbolicationInput = {
   frameTable: RawFrameTable;
-  funcTable: FuncTable;
+  funcTable: RawFuncTable;
   sourceLocationTable: SourceLocationTable;
   sources: SourceTable;
   stringArray: string[];
@@ -188,7 +189,7 @@ export function symbolicateWithSourceMaps(
  */
 function _identifyToSymbolicate(
   frameTable: RawFrameTable,
-  funcTable: FuncTable,
+  funcTable: RawFuncTable,
   sources: SourceTable
 ): {
   funcsToSymbolicate: IndexIntoFuncTable[];
@@ -211,10 +212,13 @@ function _identifyToSymbolicate(
       eligibility = _isFuncSymbolicable(funcIndex, funcTable, sources) ? 1 : 2;
       funcEligibility[funcIndex] = eligibility;
 
-      if (eligibility === 1 && funcTable.originalLocation[funcIndex] === null) {
-        const funcLine = funcTable.lineNumber[funcIndex];
-        const funcCol = funcTable.columnNumber[funcIndex];
-        if (funcLine !== null && funcCol !== null) {
+      if (eligibility === 1) {
+        const funcFlags = funcTable.flags[funcIndex];
+        if (
+          (funcFlags & FuncFlag.HasOriginalLocation) === 0 &&
+          (funcFlags & FuncFlag.HasLine) !== 0 &&
+          (funcFlags & FuncFlag.HasColumn) !== 0
+        ) {
           funcsToSymbolicate.push(funcIndex);
         }
       }
@@ -237,16 +241,14 @@ function _identifyToSymbolicate(
 
 function _isFuncSymbolicable(
   funcIndex: IndexIntoFuncTable,
-  funcTable: FuncTable,
+  funcTable: RawFuncTable,
   sources: SourceTable
 ): boolean {
-  if (!funcTable.isJS[funcIndex]) {
+  const flags = funcTable.flags[funcIndex];
+  if ((flags & FuncFlag.IsJS) === 0 || (flags & FuncFlag.HasSource) === 0) {
     return false;
   }
   const sourceIndex = funcTable.source[funcIndex];
-  if (sourceIndex === null) {
-    return false;
-  }
   return sources.sourceMapURL[sourceIndex] !== null;
 }
 
@@ -337,19 +339,19 @@ function _buildSourceMapSymbolicationResponse(
 
   // Function definitions. These get an original source file.
   for (const funcIndex of funcsToSymbolicate) {
-    const sourceIndex = funcTable.source[funcIndex];
-    if (sourceIndex === null) {
+    const funcFlags = funcTable.flags[funcIndex];
+    const requiredFlags =
+      FuncFlag.HasSource | FuncFlag.HasLine | FuncFlag.HasColumn;
+    if ((funcFlags & requiredFlags) !== requiredFlags) {
       continue;
     }
+    const sourceIndex = funcTable.source[funcIndex];
     const consumer = sourceMapStore.getConsumer(sourceIndex);
     if (consumer === null) {
       continue;
     }
     const line = funcTable.lineNumber[funcIndex];
     const column = funcTable.columnNumber[funcIndex];
-    if (line === null || column === null) {
-      continue;
-    }
     const remap = _remapPosition(
       consumer,
       line,
@@ -407,10 +409,11 @@ function _buildSourceMapSymbolicationResponse(
   // inlined code it may differ (e.g. a function from utils.ts inlined into
   // app.ts maps frames back to utils.ts).
   for (const frameIndex of framesToSymbolicate) {
-    const sourceIndex = funcTable.source[frameTable.func[frameIndex]];
-    if (sourceIndex === null) {
+    const funcIndex = frameTable.func[frameIndex];
+    if ((funcTable.flags[funcIndex] & FuncFlag.HasSource) === 0) {
       continue;
     }
+    const sourceIndex = funcTable.source[funcIndex];
     const consumer = sourceMapStore.getConsumer(sourceIndex);
     if (consumer === null) {
       continue;
@@ -956,7 +959,7 @@ export function applySourceMapSymbolicationResponse(
   shared: RawProfileSharedData,
   response: SourceMapSymbolicationResponse
 ): {
-  newFuncTable: FuncTable;
+  newFuncTable: RawFuncTable;
   newFrameTable: RawFrameTable;
   newSourceLocationTable: SourceLocationTable;
   newSources: SourceTable;
@@ -965,7 +968,7 @@ export function applySourceMapSymbolicationResponse(
   const { funcTable, frameTable, sourceLocationTable, sources, stringArray } =
     shared;
 
-  const newFuncTable = shallowCloneFuncTable(funcTable);
+  const newFuncTable = getRawFuncTableBuilderWithExistingContents(funcTable);
   const newFrameTable = getRawFrameTableBuilderWithExistingContents(frameTable);
   const newSourceLocationTable =
     shallowCloneSourceLocationTable(sourceLocationTable);
@@ -1006,7 +1009,7 @@ export function applySourceMapSymbolicationResponse(
     // A concurrent run got here first. Skip the whole entry: the row and
     // the name go together; writing a name without a sourceLocationTable row
     // would be inconsistent.
-    if (newFuncTable.originalLocation[funcIndex] !== null) {
+    if ((newFuncTable.flags[funcIndex] & FuncFlag.HasOriginalLocation) !== 0) {
       continue;
     }
     const sourceIndex = urlToSourceIndex.get(resolution.originalSource);
@@ -1019,6 +1022,7 @@ export function applySourceMapSymbolicationResponse(
     newSourceLocationTable.column.push(resolution.originalColumn);
     newSourceLocationTable.length++;
     newFuncTable.originalLocation[funcIndex] = rowIndex;
+    newFuncTable.flags[funcIndex] |= FuncFlag.HasOriginalLocation;
     if (resolution.name !== null) {
       newFuncTable.name[funcIndex] = stringTable.indexForString(
         resolution.name
@@ -1053,7 +1057,7 @@ export function applySourceMapSymbolicationResponse(
   }
 
   return {
-    newFuncTable,
+    newFuncTable: finishRawFuncTableBuilder(newFuncTable),
     newFrameTable: finishRawFrameTableBuilder(newFrameTable),
     newSourceLocationTable,
     newSources,
diff --git a/src/profile-logic/symbolication.ts b/src/profile-logic/symbolication.ts
index 76a7dd71a1..8bc6ccf39a 100644
--- a/src/profile-logic/symbolication.ts
+++ b/src/profile-logic/symbolication.ts
@@ -4,14 +4,16 @@
 import {
   getRawStackTableBuilder,
   finishRawFrameTableBuilder,
+  finishRawFuncTableBuilder,
   finishRawStackTableBuilder,
-  shallowCloneFuncTable,
+  getRawFuncTableBuilderWithExistingContents,
   finishRawNativeSymbolTableBuilder,
   getRawNativeSymbolTableBuilderWithExistingContents,
   getRawFrameTableBuilderWithExistingContents,
 } from './data-structures';
 import type {
   RawFrameTableBuilder,
+  RawFuncTableBuilder,
   RawNativeSymbolTableBuilder,
 } from './data-structures';
 import { SymbolsNotFoundError } from './errors';
@@ -21,7 +23,6 @@ import type {
   RawProfileSharedData,
   RawThread,
   RawStackTable,
-  FuncTable,
   SourceTable,
   IndexIntoFuncTable,
   IndexIntoFrameTable,
@@ -34,7 +35,7 @@ import type {
   CallNodePath,
   Lib,
 } from 'firefox-profiler/types';
-import { FrameFlag } from 'firefox-profiler/types';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types';
 import type {
   AbstractSymbolStore,
   AddressResult,
@@ -243,7 +244,7 @@ export type FuncToFuncsMap = Map<IndexIntoFuncTable, IndexIntoFuncTable[]>;
 // These are created once per batch and mutated in place by each step.
 type SymbolicationTables = {
   frameTable: RawFrameTableBuilder;
-  funcTable: FuncTable;
+  funcTable: RawFuncTableBuilder;
   nativeSymbols: RawNativeSymbolTableBuilder;
   sources: SourceTable;
   // Maps a filename string index to the index of the native (id === null)
@@ -350,11 +351,11 @@ function getSymbolicationInfo(
       funcsByLib.set(libIndex, funcs);
     }
     funcs.add(funcIndex);
-    if (!resourceForLib.has(libIndex)) {
-      const resourceIndex = funcTable.resource[funcIndex];
-      if (resourceIndex !== -1) {
-        resourceForLib.set(libIndex, resourceIndex);
-      }
+    if (
+      !resourceForLib.has(libIndex) &&
+      (funcTable.flags[funcIndex] & FuncFlag.HasResource) !== 0
+    ) {
+      resourceForLib.set(libIndex, funcTable.resource[funcIndex]);
     }
   }
 
@@ -546,7 +547,9 @@ export function applySymbolicationSteps(
   const frameTable = getRawFrameTableBuilderWithExistingContents(
     oldShared.frameTable
   );
-  const funcTable = shallowCloneFuncTable(oldShared.funcTable);
+  const funcTable = getRawFuncTableBuilderWithExistingContents(
+    oldShared.funcTable
+  );
   const nativeSymbols = getRawNativeSymbolTableBuilderWithExistingContents(
     oldShared.nativeSymbols
   );
@@ -583,7 +586,7 @@ export function applySymbolicationSteps(
   let shared: RawProfileSharedData = {
     ...oldShared,
     frameTable: finishRawFrameTableBuilder(frameTable),
-    funcTable,
+    funcTable: finishRawFuncTableBuilder(funcTable),
     nativeSymbols: finishRawNativeSymbolTableBuilder(nativeSymbols),
   };
 
@@ -838,8 +841,8 @@ function _partiallyApplySymbolicationStep(
     if (addressResult === undefined) {
       const symbolName = nativeSymbols.name[nativeSymbolIndex];
       let fileNameIndex = null;
-      const sourceIndex = funcTable.source[oldFunc];
-      if (sourceIndex !== null) {
+      if ((funcTable.flags[oldFunc] & FuncFlag.HasSource) !== 0) {
+        const sourceIndex = funcTable.source[oldFunc];
         fileNameIndex = sources.filename[sourceIndex];
       }
       addressResult = {
@@ -885,18 +888,31 @@ function _partiallyApplySymbolicationStep(
       let funcIndex = funcKeyToFuncMap.get(funcKey);
       if (funcIndex === undefined) {
         funcIndex = availableFuncIter.next().value;
+        const preservedFlagsMask = FuncFlag.IsJS | FuncFlag.RelevantForJS;
         if (funcIndex === undefined) {
           // Need a new func.
           funcIndex = funcTable.length;
-          funcTable.isJS[funcIndex] = funcTable.isJS[oldFunc];
-          funcTable.relevantForJS[funcIndex] = funcTable.relevantForJS[oldFunc];
+          funcTable.flags[funcIndex] =
+            (funcTable.flags[oldFunc] & preservedFlagsMask) |
+            FuncFlag.HasResource;
           funcTable.resource[funcIndex] = resourceIndex;
-          funcTable.source[funcIndex] = null;
-          funcTable.lineNumber[funcIndex] = null;
-          funcTable.columnNumber[funcIndex] = null;
-          funcTable.originalLocation[funcIndex] = null;
+          funcTable.source[funcIndex] = 0;
+          funcTable.lineNumber[funcIndex] = 0;
+          funcTable.columnNumber[funcIndex] = 0;
+          funcTable.originalLocation[funcIndex] = 0;
           // The name field will be filled below.
           funcTable.length++;
+        } else {
+          // Reuse an existing func slot: preserve IsJS/RelevantForJS, set
+          // HasResource, and clear the other flag bits since we're overwriting
+          // the source/line/column/originalLocation columns below.
+          funcTable.flags[funcIndex] =
+            (funcTable.flags[funcIndex] & preservedFlagsMask) |
+            FuncFlag.HasResource;
+          funcTable.resource[funcIndex] = resourceIndex;
+          funcTable.lineNumber[funcIndex] = 0;
+          funcTable.columnNumber[funcIndex] = 0;
+          funcTable.originalLocation[funcIndex] = 0;
         }
         funcTable.name[funcIndex] = functionStringIndex;
         // Store filename in sources table if we have one
@@ -916,8 +932,10 @@ function _partiallyApplySymbolicationStep(
             sourceIndexForNativeFilename.set(fileNameStringIndex, sourceIndex);
           }
           funcTable.source[funcIndex] = sourceIndex;
+          funcTable.flags[funcIndex] |= FuncFlag.HasSource;
         } else {
-          funcTable.source[funcIndex] = null;
+          funcTable.source[funcIndex] = 0;
+          funcTable.flags[funcIndex] &= ~FuncFlag.HasSource;
         }
         funcKeyToFuncMap.set(funcKey, funcIndex);
       }
diff --git a/src/profile-logic/transforms.ts b/src/profile-logic/transforms.ts
index 39d0bb18fd..2a8f54642c 100644
--- a/src/profile-logic/transforms.ts
+++ b/src/profile-logic/transforms.ts
@@ -47,7 +47,7 @@ import type {
   CategoryList,
   ProfileIndexTranslationMaps,
 } from 'firefox-profiler/types';
-import { FrameFlag } from 'firefox-profiler/types';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types';
 import type { CallNodeInfo } from 'firefox-profiler/profile-logic/call-node-info';
 import type { StringTable } from 'firefox-profiler/utils/string-table';
 import {
@@ -717,7 +717,10 @@ function _collapseResourceInCallNodePath(
     callNodePath
       // Map any collapsed functions into the collapsedFuncIndex
       .map((pathFuncIndex) => {
-        return funcTable.resource[pathFuncIndex] === resourceIndex
+        const hasResource =
+          (funcTable.flags[pathFuncIndex] & FuncFlag.HasResource) !== 0;
+        return hasResource &&
+          funcTable.resource[pathFuncIndex] === resourceIndex
           ? collapsedFuncIndex
           : pathFuncIndex;
       })
@@ -990,8 +993,10 @@ export function collapseResource(
   const newFrameTableFuncCol = frameTable.func.slice();
   for (let i = 0; i < frameTable.length; i++) {
     const funcIndex = frameTable.func[i];
-    const resourceIndex = funcTable.resource[funcIndex];
-    if (resourceIndex === resourceIndexToCollapse) {
+    if (
+      (funcTable.flags[funcIndex] & FuncFlag.HasResource) !== 0 &&
+      funcTable.resource[funcIndex] === resourceIndexToCollapse
+    ) {
       newFrameTableFuncCol[i] = collapsedFuncIndex;
     }
   }
@@ -1200,8 +1205,9 @@ const FUNC_MATCHES = {
   combined: (_thread: Thread, _funcIndex: IndexIntoFuncTable) => true,
   cpp: (thread: Thread, funcIndex: IndexIntoFuncTable): boolean => {
     const { funcTable, stringTable } = thread;
+    const funcFlags = funcTable.flags[funcIndex];
     // Return quickly if this is a JS frame.
-    if (thread.funcTable.isJS[funcIndex]) {
+    if ((funcFlags & FuncFlag.IsJS) !== 0) {
       return false;
     }
 
@@ -1211,13 +1217,15 @@ const FUNC_MATCHES = {
     // frames are not associated with a shared library and thus have no resource
     const locationString = stringTable.getString(funcTable.name[funcIndex]);
     const isProbablyJitCode =
-      funcTable.resource[funcIndex] === -1 && locationString.startsWith('0x');
+      (funcFlags & FuncFlag.HasResource) === 0 &&
+      locationString.startsWith('0x');
     return !isProbablyJitCode;
   },
   js: (thread: Thread, funcIndex: IndexIntoFuncTable): boolean => {
     return (
-      thread.funcTable.isJS[funcIndex] ||
-      thread.funcTable.relevantForJS[funcIndex]
+      (thread.funcTable.flags[funcIndex] &
+        (FuncFlag.IsJS | FuncFlag.RelevantForJS)) !==
+      0
     );
   },
 };
@@ -1657,7 +1665,7 @@ export function getBacktraceItemsForStack(
       return {
         funcName: stringTable.getString(funcTable.name[funcIndex]),
         category,
-        isFrameLabel: funcTable.resource[funcIndex] === -1,
+        isFrameLabel: (funcTable.flags[funcIndex] & FuncFlag.HasResource) === 0,
         origin: getOriginAnnotationForFunc(
           funcIndex,
           frameIndex,
diff --git a/src/profile-logic/wasm-symbolication.ts b/src/profile-logic/wasm-symbolication.ts
index a28d227e4f..f831302529 100644
--- a/src/profile-logic/wasm-symbolication.ts
+++ b/src/profile-logic/wasm-symbolication.ts
@@ -10,6 +10,7 @@
 // placeholders in the profile's funcTable.
 
 import type { Profile } from 'firefox-profiler/types/profile';
+import { FuncFlag } from 'firefox-profiler/types/profile';
 import { StringTable } from 'firefox-profiler/utils/string-table';
 
 export interface WasmSymbolicationSpec {
@@ -190,8 +191,11 @@ export function applyWasmSymbolication(
     let updated = 0;
     let missingNames = 0;
     for (let f = 0; f < funcTable.length; f++) {
+      if ((funcTable.flags[f] & FuncFlag.HasSource) === 0) {
+        continue;
+      }
       const sourceIdx = funcTable.source[f];
-      if (sourceIdx === null || !sourceIndexSet.has(sourceIdx)) {
+      if (!sourceIndexSet.has(sourceIdx)) {
         continue;
       }
       const oldName = stringArray[funcTable.name[f]];
diff --git a/src/profile-query/function-annotate.ts b/src/profile-query/function-annotate.ts
index fec5c6b289..f9125ef45b 100644
--- a/src/profile-query/function-annotate.ts
+++ b/src/profile-query/function-annotate.ts
@@ -21,6 +21,7 @@ import {
   getNativeSymbolsForFunc,
   findAddressProofForFile,
   getOriginalPositionForFrame,
+  computeFuncTableFromRawFuncTable,
 } from 'firefox-profiler/profile-logic/profile-data';
 import { fetchAssembly } from 'firefox-profiler/utils/fetch-assembly';
 import { fetchSource } from 'firefox-profiler/utils/fetch-source';
@@ -33,6 +34,7 @@ import type {
   SamplesLikeTable,
   Thread,
 } from 'firefox-profiler/types';
+import { FuncFlag } from 'firefox-profiler/types';
 import type {
   FunctionAnnotateResult,
   AnnotateMode,
@@ -81,8 +83,8 @@ async function fetchSourceAnnotation(
   contextOption: string
 ): Promise<SourceAnnotationResult> {
   const warnings: string[] = [];
-  const compiledSourceIndex = profile.shared.funcTable.source[funcIndex];
-  if (compiledSourceIndex === null) {
+  const rawFuncTable = profile.shared.funcTable;
+  if ((rawFuncTable.flags[funcIndex] & FuncFlag.HasSource) === 0) {
     if (mode === 'src') {
       warnings.push(
         `Function ${functionHandle} has no source index. Use --mode asm for assembly view.`
@@ -90,6 +92,7 @@ async function fetchSourceAnnotation(
     }
     return { annotation: null, warnings };
   }
+  const compiledSourceIndex = rawFuncTable.source[funcIndex];
 
   const {
     stackTable,
@@ -338,7 +341,8 @@ export async function functionAnnotate(
 ): Promise<FunctionAnnotateResult> {
   const state = store.getState();
   const profile = getProfile(state);
-  const { funcTable, stringArray, resourceTable } = profile.shared;
+  const { stringArray, resourceTable } = profile.shared;
+  const funcTable = computeFuncTableFromRawFuncTable(profile.shared.funcTable);
 
   const funcIndex = parseFunctionHandle(functionHandle, funcTable.length);
   const funcName = stringArray[funcTable.name[funcIndex]];
diff --git a/src/profile-query/function-list.ts b/src/profile-query/function-list.ts
index 4ba06cfd90..78772a2dff 100644
--- a/src/profile-query/function-list.ts
+++ b/src/profile-query/function-list.ts
@@ -9,7 +9,7 @@ import type {
   FuncTable,
   ResourceTable,
 } from 'firefox-profiler/types';
-import { ResourceType, FrameFlag } from 'firefox-profiler/types';
+import { ResourceType, FrameFlag, FuncFlag } from 'firefox-profiler/types';
 import { getFunctionHandle } from './function-map';
 
 /**
@@ -46,11 +46,11 @@ export function getLibNameForFunc(
   resourceTable: ResourceTable,
   stringArray: string[]
 ): string | null {
+  if ((funcTable.flags[funcIndex] & FuncFlag.HasResource) === 0) {
+    return null;
+  }
   const resourceIndex = funcTable.resource[funcIndex];
-  if (
-    resourceIndex === -1 ||
-    resourceTable.type[resourceIndex] !== ResourceType.Library
-  ) {
+  if (resourceTable.type[resourceIndex] !== ResourceType.Library) {
     return null;
   }
   return stringArray[resourceTable.name[resourceIndex]];
@@ -384,8 +384,8 @@ export function formatFunctionNameWithLibrary(
   );
   // The func's resource carries the library name for native code, and the
   // origin / URL for JS code.
-  const resourceIndex = thread.funcTable.resource[funcIndex];
-  if (resourceIndex !== -1) {
+  if ((thread.funcTable.flags[funcIndex] & FuncFlag.HasResource) !== 0) {
+    const resourceIndex = thread.funcTable.resource[funcIndex];
     const resourceName = thread.stringTable.getString(
       thread.resourceTable.name[resourceIndex]
     );
diff --git a/src/profile-query/index.ts b/src/profile-query/index.ts
index 0b6826c452..9e17c68560 100644
--- a/src/profile-query/index.ts
+++ b/src/profile-query/index.ts
@@ -147,7 +147,11 @@ import type {
 } from './types';
 import type { CallTreeCollectionOptions } from './formatters/call-tree';
 
-import { getThreadsKey } from 'firefox-profiler/profile-logic/profile-data';
+import {
+  getThreadsKey,
+  computeFuncTableFromRawFuncTable,
+} from 'firefox-profiler/profile-logic/profile-data';
+import { FuncFlag } from 'firefox-profiler/types';
 import type { Store } from '../types/store';
 
 function toSourceEntry(source: EligibleSource): SourceEntry {
@@ -1280,7 +1284,10 @@ export class ProfileQuerier {
   ): Promise<WithContext<FunctionExpandResult>> {
     const state = this._store.getState();
     const profile = getProfile(state);
-    const { funcTable, resourceTable, stringArray } = profile.shared;
+    const { resourceTable, stringArray } = profile.shared;
+    const funcTable = computeFuncTableFromRawFuncTable(
+      profile.shared.funcTable
+    );
 
     // Look up the function
     const funcIndex = parseFunctionHandle(functionHandle, funcTable.length);
@@ -1309,19 +1316,24 @@ export class ProfileQuerier {
   ): Promise<WithContext<FunctionInfoResult>> {
     const state = this._store.getState();
     const profile = getProfile(state);
-    const { funcTable, resourceTable, stringArray } = profile.shared;
+    const { resourceTable, stringArray } = profile.shared;
+    const funcTable = computeFuncTableFromRawFuncTable(
+      profile.shared.funcTable
+    );
 
     // Look up the function
     const funcIndex = parseFunctionHandle(functionHandle, funcTable.length);
     const funcName = stringArray[funcTable.name[funcIndex]];
-    const resourceIndex = funcTable.resource[funcIndex];
-    const isJS = funcTable.isJS[funcIndex];
-    const relevantForJS = funcTable.relevantForJS[funcIndex];
+    const funcFlags = funcTable.flags[funcIndex];
+    const isJS = (funcFlags & FuncFlag.IsJS) !== 0;
+    const relevantForJS = (funcFlags & FuncFlag.RelevantForJS) !== 0;
+    const hasResource = (funcFlags & FuncFlag.HasResource) !== 0;
 
     let resource: FunctionInfoResult['resource'];
     let library: FunctionInfoResult['library'];
 
-    if (resourceIndex !== -1) {
+    if (hasResource) {
+      const resourceIndex = funcTable.resource[funcIndex];
       resource = {
         name: stringArray[resourceTable.name[resourceIndex]],
         index: resourceIndex,
diff --git a/src/selectors/per-thread/index.ts b/src/selectors/per-thread/index.ts
index 5460a7a95d..af4d8b081c 100644
--- a/src/selectors/per-thread/index.ts
+++ b/src/selectors/per-thread/index.ts
@@ -32,6 +32,7 @@ import type {
   ThreadsKey,
   State,
 } from 'firefox-profiler/types';
+import { FuncFlag } from 'firefox-profiler/types';
 
 import type { TimingsForPath } from '../../profile-logic/profile-data';
 
@@ -217,7 +218,7 @@ export const selectedNodeSelectors: NodeSelectors = (() => {
       }
 
       const funcIndex = ProfileData.getLeafFuncIndex(selectedPath);
-      return funcTable.isJS[funcIndex];
+      return (funcTable.flags[funcIndex] & FuncFlag.IsJS) !== 0;
     }
   );
 
diff --git a/src/selectors/profile.ts b/src/selectors/profile.ts
index 2d03725270..d879f17dac 100644
--- a/src/selectors/profile.ts
+++ b/src/selectors/profile.ts
@@ -21,6 +21,7 @@ import {
   computeTabToThreadIndexesMap,
   computeStackTableFromRawStackTable,
   computeFrameTableFromRawFrameTable,
+  computeFuncTableFromRawFuncTable,
   computeNativeSymbolTableFromRawNativeSymbolTable,
   reserveFunctionsForCollapsedResources,
   computeSamplesTableFromRawSamplesTable,
@@ -292,6 +293,11 @@ export const getNativeSymbolTable: Selector<NativeSymbolTable> = createSelector(
   computeNativeSymbolTableFromRawNativeSymbolTable
 );
 
+export const getFuncTable: Selector<FuncTable> = createSelector(
+  (state: State) => getRawProfileSharedData(state).funcTable,
+  computeFuncTableFromRawFuncTable
+);
+
 export const getStackTable: Selector<StackTable> = createSelector(
   (state: State) => getRawProfileSharedData(state).stackTable,
   getFrameTable,
diff --git a/src/test/components/CallNodeContextMenu.test.tsx b/src/test/components/CallNodeContextMenu.test.tsx
index 0e032e73cf..a5062bd4a1 100644
--- a/src/test/components/CallNodeContextMenu.test.tsx
+++ b/src/test/components/CallNodeContextMenu.test.tsx
@@ -28,6 +28,7 @@ import { updateBrowserConnectionStatus } from 'firefox-profiler/actions/app';
 import { simulateWebChannel } from '../fixtures/mocks/web-channel';
 import { retrieveProfileFromBrowser } from '../../actions/receive-profile';
 import type { GeckoProfile } from 'firefox-profiler/types';
+import { FuncFlag } from 'firefox-profiler/types';
 
 describe('calltree/CallNodeContextMenu', function () {
   // Provide a store with a useful profile to assert context menu operations off of.
@@ -71,15 +72,19 @@ describe('calltree/CallNodeContextMenu', function () {
 
     const { funcTable } = profile.shared;
 
+    const jsFuncFlags =
+      FuncFlag.HasSource | FuncFlag.HasLine | FuncFlag.HasColumn;
     const funcIndexA = funcNames.indexOf('A.js');
     funcTable.source[funcIndexA] = sourceIndex;
     funcTable.lineNumber[funcIndexA] = 1;
     funcTable.columnNumber[funcIndexA] = 111;
+    funcTable.flags[funcIndexA] |= jsFuncFlags;
 
     const funcIndexB = funcNames.indexOf('B.js');
     funcTable.source[funcIndexB] = sourceIndex;
     funcTable.lineNumber[funcIndexB] = 2;
     funcTable.columnNumber[funcIndexB] = 222;
+    funcTable.flags[funcIndexB] |= jsFuncFlags;
 
     const store = storeWithProfile(profile);
     store.dispatch(changeRightClickedCallNode(0, [funcIndexA, funcIndexB]));
diff --git a/src/test/components/FlameGraph.test.tsx b/src/test/components/FlameGraph.test.tsx
index 5d39138f5e..b91f50cd39 100644
--- a/src/test/components/FlameGraph.test.tsx
+++ b/src/test/components/FlameGraph.test.tsx
@@ -48,6 +48,7 @@ import { mockRaf } from '../fixtures/mocks/request-animation-frame';
 import { autoMockElementSize } from '../fixtures/mocks/element-size';
 
 import type { CssPixels } from 'firefox-profiler/types';
+import { FuncFlag } from 'firefox-profiler/types';
 
 const GRAPH_WIDTH = 200;
 const GRAPH_HEIGHT = 300;
@@ -356,6 +357,8 @@ function setupFlameGraph() {
     funcTable.lineNumber[funcIndex] = funcIndex + 10;
     funcTable.columnNumber[funcIndex] = funcIndex + 100;
     funcTable.source[funcIndex] = defaultSourceIndex;
+    funcTable.flags[funcIndex] |=
+      FuncFlag.HasLine | FuncFlag.HasColumn | FuncFlag.HasSource;
   }
 
   funcTable.source[funcNamesDict.B] = bSourceIndex;
diff --git a/src/test/fixtures/profile-summary.ts b/src/test/fixtures/profile-summary.ts
index 6f35567fc5..45478b3168 100644
--- a/src/test/fixtures/profile-summary.ts
+++ b/src/test/fixtures/profile-summary.ts
@@ -8,9 +8,9 @@ import type {
   IndexIntoStackTable,
   RawStackTable,
   RawFrameTable,
-  FuncTable,
+  RawFuncTable,
 } from 'firefox-profiler/types';
-import { FrameFlag } from 'firefox-profiler/types';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types';
 
 /**
  * Walks a raw profile and asserts a set of structural invariants. Throws
@@ -82,14 +82,13 @@ export function assertProfileIntegrity(profile: Profile): void {
         `funcTable.name[${fn}] = ${name} is not a valid integer index in [0, ${stringCount})`
       );
     }
-    const res = funcTable.resource[fn];
-    if (
-      !Number.isInteger(res) ||
-      (res !== -1 && (res < 0 || res >= resourceTable.length))
-    ) {
-      throw new Error(
-        `funcTable.resource[${fn}] = ${res} is not a valid integer index in [0, ${resourceTable.length}) or -1`
-      );
+    if ((funcTable.flags[fn] & FuncFlag.HasResource) !== 0) {
+      const res = funcTable.resource[fn];
+      if (!Number.isInteger(res) || res < 0 || res >= resourceTable.length) {
+        throw new Error(
+          `funcTable.resource[${fn}] = ${res} is not a valid integer index in [0, ${resourceTable.length})`
+        );
+      }
     }
   }
 
@@ -459,7 +458,7 @@ function renderStackPath(
   stack: IndexIntoStackTable | null,
   stackTable: RawStackTable,
   frameTable: RawFrameTable,
-  funcTable: FuncTable,
+  funcTable: RawFuncTable,
   stringArray: string[]
 ): string {
   if (stack === null) {
diff --git a/src/test/fixtures/profiles/call-nodes.ts b/src/test/fixtures/profiles/call-nodes.ts
index dfe3282647..eee03d3455 100644
--- a/src/test/fixtures/profiles/call-nodes.ts
+++ b/src/test/fixtures/profiles/call-nodes.ts
@@ -43,14 +43,13 @@ export default function getProfile(): Profile {
 
   // Be explicit about table creation so flow errors are really readable.
   const funcTable: FuncTable = {
-    name: funcNames,
-    isJS: Array(funcNames.length).fill(false),
-    resource: Array(funcNames.length).fill(-1),
-    relevantForJS: Array(funcNames.length).fill(false),
-    source: Array(funcNames.length).fill(null),
-    lineNumber: Array(funcNames.length).fill(null),
-    columnNumber: Array(funcNames.length).fill(null),
-    originalLocation: Array(funcNames.length).fill(null),
+    flags: new Uint8Array(funcNames.length),
+    name: new Int32Array(funcNames),
+    resource: new Int32Array(funcNames.length),
+    source: new Int32Array(funcNames.length),
+    lineNumber: new Int32Array(funcNames.length),
+    columnNumber: new Int32Array(funcNames.length),
+    originalLocation: new Int32Array(funcNames.length),
     length: funcNames.length,
   };
 
diff --git a/src/test/fixtures/utils.ts b/src/test/fixtures/utils.ts
index c955a2d233..cabb0e3707 100644
--- a/src/test/fixtures/utils.ts
+++ b/src/test/fixtures/utils.ts
@@ -19,6 +19,7 @@ import {
   createThreadFromDerivedTables,
   computeStackTableFromRawStackTable,
   computeFrameTableFromRawFrameTable,
+  computeFuncTableFromRawFuncTable,
   computeNativeSymbolTableFromRawNativeSymbolTable,
   computeSamplesTableFromRawSamplesTable,
   computeJsAllocationsTableFromRawJsAllocationsTable,
@@ -154,6 +155,7 @@ export function computeThreadFromRawThread(
     shared.frameTable,
     categories
   );
+  const funcTable = computeFuncTableFromRawFuncTable(shared.funcTable);
   const nativeSymbols = computeNativeSymbolTableFromRawNativeSymbolTable(
     shared.nativeSymbols
   );
@@ -188,7 +190,7 @@ export function computeThreadFromRawThread(
     samples,
     stackTable,
     frameTable,
-    shared.funcTable,
+    funcTable,
     nativeSymbols,
     shared.resourceTable,
     stringTable,
diff --git a/src/test/integration/profiler-edit/__snapshots__/profiler-edit.test.ts.snap b/src/test/integration/profiler-edit/__snapshots__/profiler-edit.test.ts.snap
index 82decd756c..f666a08608 100644
--- a/src/test/integration/profiler-edit/__snapshots__/profiler-edit.test.ts.snap
+++ b/src/test/integration/profiler-edit/__snapshots__/profiler-edit.test.ts.snap
@@ -87,7 +87,7 @@ Object {
     "markerSchema": Array [],
     "oscpu": "macOS 14.6.1",
     "pausedRanges": Array [],
-    "preprocessedProfileVersion": 74,
+    "preprocessedProfileVersion": 75,
     "processType": 0,
     "product": "a.out",
     "sampleUnits": Object {
@@ -593,50 +593,50 @@ Object {
     },
     "funcTable": Object {
       "columnNumber": Array [
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
-      "isJS": Array [
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
+      "flags": Array [
+        4,
+        4,
+        4,
+        4,
+        4,
+        4,
+        4,
+        4,
+        4,
+        4,
+        4,
+        4,
+        4,
       ],
       "length": 13,
       "lineNumber": Array [
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
       "name": Array [
         6,
@@ -654,34 +654,19 @@ Object {
         18,
       ],
       "originalLocation": Array [
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-      ],
-      "relevantForJS": Array [
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
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diff --git a/src/test/store/__snapshots__/profile-view.test.ts.snap b/src/test/store/__snapshots__/profile-view.test.ts.snap
index eed3a0100e..f020e95137 100644
--- a/src/test/store/__snapshots__/profile-view.test.ts.snap
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+      0,
+    ],
+    "flags": Uint8Array [
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
     ],
     "length": 9,
-    "lineNumber": Array [
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-    ],
-    "name": Array [
+    "lineNumber": Int32Array [
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+    ],
+    "name": Int32Array [
       0,
       1,
       2,
@@ -3866,49 +3822,38 @@ Object {
       7,
       8,
     ],
-    "originalLocation": Array [
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-    ],
-    "relevantForJS": Array [
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
-    ],
-    "resource": Array [
-      -1,
-      -1,
-      -1,
-      -1,
-      -1,
-      -1,
-      -1,
-      -1,
-      -1,
+    "originalLocation": Int32Array [
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
     ],
-    "source": Array [
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
+    "resource": Int32Array [
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+    ],
+    "source": Int32Array [
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
     ],
   },
   "isJsTracer": undefined,
@@ -4217,41 +4162,41 @@ Object {
     ],
   },
   "funcTable": Object {
-    "columnNumber": Array [
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-    ],
-    "isJS": Array [
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
+    "columnNumber": Int32Array [
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+    ],
+    "flags": Uint8Array [
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
     ],
     "length": 9,
-    "lineNumber": Array [
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-    ],
-    "name": Array [
+    "lineNumber": Int32Array [
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+    ],
+    "name": Int32Array [
       0,
       1,
       2,
@@ -4262,49 +4207,38 @@ Object {
       7,
       8,
     ],
-    "originalLocation": Array [
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-    ],
-    "relevantForJS": Array [
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
-      false,
-    ],
-    "resource": Array [
-      -1,
-      -1,
-      -1,
-      -1,
-      -1,
-      -1,
-      -1,
-      -1,
-      -1,
+    "originalLocation": Int32Array [
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+    ],
+    "resource": Int32Array [
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
     ],
-    "source": Array [
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
-      null,
+    "source": Int32Array [
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
     ],
   },
   "isJsTracer": undefined,
diff --git a/src/test/store/js-tracer.test.ts b/src/test/store/js-tracer.test.ts
index ca5e5335e2..1f30bb9643 100644
--- a/src/test/store/js-tracer.test.ts
+++ b/src/test/store/js-tracer.test.ts
@@ -19,6 +19,7 @@ import {
 } from '../fixtures/profiles/processed-profile';
 
 import type { Profile } from 'firefox-profiler/types';
+import { FuncFlag } from 'firefox-profiler/types';
 
 describe('jsTracerFixed', function () {
   function fixTiming(events: TestDefinedJsTracerEvent[]) {
@@ -349,6 +350,11 @@ describe('selectors/getJsTracerTiming', function () {
         const fooLine = 3;
         const fooColumn = 5;
         const { shared } = profile;
+        const jsFuncFlags =
+          FuncFlag.IsJS |
+          FuncFlag.HasLine |
+          FuncFlag.HasColumn |
+          FuncFlag.HasSource;
 
         shared.funcTable.lineNumber[foo] = fooLine;
         shared.funcTable.columnNumber[foo] = fooColumn;
@@ -357,6 +363,7 @@ describe('selectors/getJsTracerTiming', function () {
           shared.sources,
           fooUrlIndex
         );
+        shared.funcTable.flags[foo] |= jsFuncFlags;
 
         const bar = funcNamesDict['Bar.js'];
         const barLine = 7;
@@ -368,6 +375,7 @@ describe('selectors/getJsTracerTiming', function () {
           shared.sources,
           barUrlIndex
         );
+        shared.funcTable.flags[bar] |= jsFuncFlags;
 
         const baz = funcNamesDict['Baz.js'];
         // Use bar's line and column information.
@@ -378,6 +386,7 @@ describe('selectors/getJsTracerTiming', function () {
           shared.sources,
           bazUrlIndex
         );
+        shared.funcTable.flags[baz] |= jsFuncFlags;
 
         // Manually update the JS tracer events to point to the right column numbers.
         jsTracer.line[2] = fooLine;
diff --git a/src/test/store/source-map-symbolication.test.ts b/src/test/store/source-map-symbolication.test.ts
index cdc798c639..f279cbf1ad 100644
--- a/src/test/store/source-map-symbolication.test.ts
+++ b/src/test/store/source-map-symbolication.test.ts
@@ -35,7 +35,7 @@ import { getProfileFromTextSamples } from '../fixtures/profiles/processed-profil
 
 import type { BrowserConnection } from '../../app-logic/browser-connection';
 import type { Profile } from 'firefox-profiler/types';
-import { FrameFlag } from 'firefox-profiler/types';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types';
 import type {
   WorkerInput,
   WorkerOutput,
@@ -133,6 +133,7 @@ function makeProfileWithJsSources(sources: SourceDescriptor[]): Profile {
   for (let i = 0; i < sources.length; i++) {
     funcTable.lineNumber[i] = 1;
     funcTable.columnNumber[i] = 10;
+    funcTable.flags[i] |= FuncFlag.HasLine | FuncFlag.HasColumn;
     frameTable.flags[i] |= FrameFlag.HasLine | FrameFlag.HasColumn;
     frameTable.line[i] = 1;
     frameTable.column[i] = 15;
diff --git a/src/test/unit/__snapshots__/profile-conversion.test.ts.snap b/src/test/unit/__snapshots__/profile-conversion.test.ts.snap
index fa71c3fb91..4f9d85b213 100644
--- a/src/test/unit/__snapshots__/profile-conversion.test.ts.snap
+++ b/src/test/unit/__snapshots__/profile-conversion.test.ts.snap
@@ -42,7 +42,7 @@ Object {
         "RefreshDriverTick",
         "Network",
       ],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "ART Trace (Android)",
       "symbolicated": true,
       "version": 36,
@@ -1022,7 +1022,7 @@ Object {
         "RefreshDriverTick",
         "Network",
       ],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "ART Trace (Android)",
       "symbolicated": true,
       "version": 36,
@@ -2305,7 +2305,7 @@ Object {
       "markerSchemaNames": Array [
         "EventDispatch",
       ],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Chrome Trace",
       "symbolicated": true,
       "version": 36,
@@ -2697,7 +2697,7 @@ Object {
       "markerSchemaNames": Array [
         "EventDispatch",
       ],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Chrome Trace",
       "symbolicated": true,
       "version": 36,
@@ -3086,7 +3086,7 @@ Object {
       "markerSchemaNames": Array [
         "EventDispatch",
       ],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Chrome Trace",
       "symbolicated": true,
       "version": 36,
@@ -3187,7 +3187,7 @@ Object {
       "markerSchemaNames": Array [
         "EventDispatch",
       ],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Chrome Trace",
       "symbolicated": true,
       "version": 36,
@@ -3540,7 +3540,7 @@ Object {
       "markerSchemaNames": Array [
         "EventDispatch",
       ],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Chrome Trace",
       "symbolicated": true,
       "version": 36,
@@ -3605,7 +3605,7 @@ Object {
       "markerSchemaNames": Array [
         "EventDispatch",
       ],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Chrome Trace",
       "symbolicated": true,
       "version": 36,
@@ -3759,7 +3759,7 @@ Object {
       "markerSchemaNames": Array [
         "EventDispatch",
       ],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Chrome Trace",
       "symbolicated": true,
       "version": 36,
@@ -3817,7 +3817,7 @@ Object {
       "importedFrom": undefined,
       "interval": 1,
       "markerSchemaNames": Array [],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Firefox",
       "symbolicated": true,
       "version": 36,
@@ -4207,7 +4207,7 @@ Object {
       "importedFrom": undefined,
       "interval": 1,
       "markerSchemaNames": Array [],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Firefox",
       "symbolicated": true,
       "version": 36,
@@ -4265,7 +4265,7 @@ Object {
       "importedFrom": undefined,
       "interval": 1,
       "markerSchemaNames": Array [],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Firefox",
       "symbolicated": true,
       "version": 36,
@@ -4323,7 +4323,7 @@ Object {
       "importedFrom": undefined,
       "interval": 1,
       "markerSchemaNames": Array [],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Firefox",
       "symbolicated": true,
       "version": 36,
@@ -4643,7 +4643,7 @@ Object {
       "importedFrom": "Simpleperf",
       "interval": 0,
       "markerSchemaNames": Array [],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "com.example.sampleapplication",
       "symbolicated": undefined,
       "version": 30,
@@ -5019,7 +5019,7 @@ Object {
       "importedFrom": "Simpleperf",
       "interval": 0,
       "markerSchemaNames": Array [],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "com.example.sampleapplication",
       "symbolicated": undefined,
       "version": 30,
@@ -5319,7 +5319,7 @@ Object {
       "importedFrom": "dhat",
       "interval": 1,
       "markerSchemaNames": Array [],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "target/debug/examples/work_log (dhat)",
       "symbolicated": true,
       "version": 36,
@@ -5452,7 +5452,7 @@ Object {
       "importedFrom": undefined,
       "interval": 1,
       "markerSchemaNames": Array [],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Flamegraph",
       "symbolicated": true,
       "version": 36,
@@ -5510,7 +5510,7 @@ Object {
       "importedFrom": undefined,
       "interval": 1,
       "markerSchemaNames": Array [],
-      "preprocessedProfileVersion": 74,
+      "preprocessedProfileVersion": 75,
       "product": "Flamegraph",
       "symbolicated": true,
       "version": 36,
diff --git a/src/test/unit/__snapshots__/profile-upgrading.test.ts.snap b/src/test/unit/__snapshots__/profile-upgrading.test.ts.snap
index 285f72f448..a4865443e4 100644
--- a/src/test/unit/__snapshots__/profile-upgrading.test.ts.snap
+++ b/src/test/unit/__snapshots__/profile-upgrading.test.ts.snap
@@ -40,7 +40,7 @@ Object {
     "oscpu": undefined,
     "physicalCPUs": undefined,
     "platform": undefined,
-    "preprocessedProfileVersion": 74,
+    "preprocessedProfileVersion": 75,
     "processType": 0,
     "product": "Firefox",
     "sampleUnits": undefined,
@@ -2310,227 +2310,227 @@ Object {
     },
     "funcTable": Object {
       "columnNumber": Array [
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
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-      "isJS": Array [
-        false,
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+      "flags": Array [
+        4,
+        4,
+        4,
+        4,
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       ],
       "length": 72,
       "lineNumber": Array [
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       "name": Array [
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@@ -2549,210 +2549,136 @@ Object {
         33,
         35,
         38,
-        40,
-        42,
-        44,
-        46,
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-        51,
-        53,
-        55,
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-        139,
-        141,
-        143,
-        145,
-        147,
-        149,
-        151,
-        153,
-      ],
-      "originalLocation": Array [
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-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
+        40,
+        42,
+        44,
+        46,
+        49,
+        51,
+        53,
+        55,
+        7,
+        60,
+        62,
+        64,
+        66,
+        68,
+        70,
+        72,
+        74,
+        76,
+        78,
+        80,
+        82,
+        84,
+        86,
+        88,
+        90,
+        92,
+        94,
+        96,
+        98,
+        100,
+        102,
+        104,
+        106,
+        108,
+        110,
+        112,
+        114,
+        116,
+        119,
+        121,
+        123,
+        125,
+        127,
+        129,
+        131,
+        133,
+        135,
+        137,
+        139,
+        141,
+        143,
+        145,
+        147,
+        149,
+        151,
+        153,
       ],
-      "relevantForJS": Array [
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
+      "originalLocation": Array [
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
       "resource": Array [
         0,
@@ -2829,78 +2755,78 @@ Object {
         1,
       ],
       "source": Array [
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
     },
     "nativeSymbols": Object {
@@ -7867,7 +7793,7 @@ Object {
     "misc": "rv:48.0",
     "oscpu": "Intel Mac OS X 10.11",
     "platform": "Macintosh",
-    "preprocessedProfileVersion": 74,
+    "preprocessedProfileVersion": 75,
     "processType": 0,
     "product": "Firefox",
     "stackwalk": 1,
@@ -8134,32 +8060,32 @@ Object {
     },
     "funcTable": Object {
       "columnNumber": Array [
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
-      "isJS": Array [
-        false,
-        false,
-        false,
-        false,
-        true,
-        false,
-        false,
+      "flags": Array [
+        0,
+        4,
+        4,
+        0,
+        29,
+        4,
+        4,
       ],
       "length": 7,
       "lineNumber": Array [
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
         34,
-        null,
-        null,
+        0,
+        0,
       ],
       "name": Array [
         5,
@@ -8171,40 +8097,31 @@ Object {
         7,
       ],
       "originalLocation": Array [
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-      ],
-      "relevantForJS": Array [
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
       "resource": Array [
-        -1,
         0,
         0,
-        -1,
+        0,
+        0,
         1,
         2,
         2,
       ],
       "source": Array [
-        null,
-        null,
-        null,
-        null,
         0,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
     },
     "nativeSymbols": Object {
@@ -9295,7 +9212,7 @@ Object {
     "misc": "rv:48.0",
     "oscpu": "Intel Mac OS X 10.11",
     "platform": "Macintosh",
-    "preprocessedProfileVersion": 74,
+    "preprocessedProfileVersion": 75,
     "processType": 0,
     "product": "Firefox",
     "stackwalk": 1,
@@ -9584,38 +9501,38 @@ Object {
     },
     "funcTable": Object {
       "columnNumber": Array [
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
-      "isJS": Array [
-        false,
-        false,
-        false,
-        false,
-        true,
-        false,
-        false,
-        false,
-        false,
+      "flags": Array [
+        0,
+        4,
+        4,
+        0,
+        29,
+        4,
+        4,
+        2,
+        2,
       ],
       "length": 9,
       "lineNumber": Array [
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
         34,
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
       ],
       "name": Array [
         6,
@@ -9629,48 +9546,37 @@ Object {
         15,
       ],
       "originalLocation": Array [
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-      ],
-      "relevantForJS": Array [
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        true,
-        true,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
       "resource": Array [
-        -1,
         0,
         0,
-        -1,
+        0,
+        0,
         1,
         2,
         2,
-        -1,
-        -1,
+        0,
+        0,
       ],
       "source": Array [
-        null,
-        null,
-        null,
-        null,
         0,
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
     },
     "nativeSymbols": Object {
@@ -10893,7 +10799,7 @@ Object {
     "misc": "rv:48.0",
     "oscpu": "Intel Mac OS X 10.11",
     "platform": "Macintosh",
-    "preprocessedProfileVersion": 74,
+    "preprocessedProfileVersion": 75,
     "processType": 0,
     "product": "Firefox",
     "stackwalk": 1,
@@ -11208,38 +11114,38 @@ Object {
     },
     "funcTable": Object {
       "columnNumber": Array [
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
-      "isJS": Array [
-        false,
-        false,
-        false,
-        false,
-        true,
-        false,
-        false,
-        false,
-        false,
+      "flags": Array [
+        0,
+        4,
+        4,
+        0,
+        29,
+        4,
+        4,
+        2,
+        2,
       ],
       "length": 9,
       "lineNumber": Array [
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
         34,
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
       ],
       "name": Array [
         7,
@@ -11253,48 +11159,37 @@ Object {
         16,
       ],
       "originalLocation": Array [
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-        null,
-      ],
-      "relevantForJS": Array [
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        false,
-        true,
-        true,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
       "resource": Array [
-        -1,
         0,
         0,
-        -1,
+        0,
+        0,
         1,
         2,
         2,
-        -1,
-        -1,
+        0,
+        0,
       ],
       "source": Array [
-        null,
-        null,
-        null,
-        null,
         0,
-        null,
-        null,
-        null,
-        null,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
       ],
     },
     "nativeSymbols": Object {
diff --git a/src/test/unit/line-timings.test.ts b/src/test/unit/line-timings.test.ts
index 4823e44fe4..c6e1b241ae 100644
--- a/src/test/unit/line-timings.test.ts
+++ b/src/test/unit/line-timings.test.ts
@@ -20,7 +20,7 @@ import type {
   IndexIntoCategoryList,
   LineNumber,
 } from 'firefox-profiler/types';
-import { FrameFlag } from 'firefox-profiler/types';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types';
 
 describe('getStackLineInfo', function () {
   it('computes results for all stacks', function () {
@@ -144,6 +144,7 @@ describe('getLineTimings for getStackLineInfo', function () {
     // Set funcTable.lineNumber to a value for the func of that frame
     const func = frameTable.func[leafFrame];
     funcTable.lineNumber[func] = 35;
+    funcTable.flags[func] |= FuncFlag.HasLine;
 
     const fileStringIndex = stringTable.indexForString('file.js');
     const fileSourceIndex = thread.sources.filename.indexOf(fileStringIndex);
@@ -202,6 +203,8 @@ describe('getLineTimings for getStackLineInfo', function () {
     sourceLocationTable.length += 2;
     funcTable.originalLocation[funcAIndex] = funcAOriginalLocationIdx;
     funcTable.originalLocation[funcBIndex] = funcBOriginalLocationIdx;
+    funcTable.flags[funcAIndex] |= FuncFlag.HasOriginalLocation;
+    funcTable.flags[funcBIndex] |= FuncFlag.HasOriginalLocation;
 
     const stackLineInfo = getStackLineInfo(
       stackTable,
@@ -394,6 +397,7 @@ describe('getTotalLineTimingsForCallNode', function () {
     // Set funcTable.lineNumber to a value for the func of that frame
     const func = frameTable.func[leafFrame];
     funcTable.lineNumber[func] = 35;
+    funcTable.flags[func] |= FuncFlag.HasLine;
 
     // Compute the line timings for the child call node.
     // The fallback should use funcTable.lineNumber[func] = 35
diff --git a/src/test/unit/merge-compare.test.ts b/src/test/unit/merge-compare.test.ts
index 6b4fc0a3c4..0c03235189 100644
--- a/src/test/unit/merge-compare.test.ts
+++ b/src/test/unit/merge-compare.test.ts
@@ -18,7 +18,7 @@ import { ensureExists } from 'firefox-profiler/utils/types';
 import { getTimeRangeIncludingAllThreads } from 'firefox-profiler/profile-logic/profile-data';
 import { StringTable } from '../../utils/string-table';
 import type { RawProfileSharedData, Profile } from 'firefox-profiler/types';
-import { ResourceType, FrameFlag } from 'firefox-profiler/types';
+import { ResourceType, FrameFlag, FuncFlag } from 'firefox-profiler/types';
 import { callTreeFromProfile, formatTree } from '../fixtures/utils';
 import { storeWithProfile } from '../fixtures/stores';
 import { addTransformToStack } from '../../actions/profile-view';
@@ -1051,7 +1051,9 @@ describe('mergeProfilesForDiffing with source tables', function () {
     sharedA.sourceLocationTable.column.push(22);
     sharedA.sourceLocationTable.length = 1;
     sharedA.funcTable.originalLocation[0] = 0;
+    sharedA.funcTable.flags[0] |= FuncFlag.HasOriginalLocation;
     sharedA.frameTable.originalLocation[0] = 0;
+    sharedA.frameTable.flags[0] |= FrameFlag.HasOriginalLocation;
 
     const sharedB = profileB.profile.shared;
     sharedB.sourceLocationTable.source.push(0);
@@ -1059,7 +1061,9 @@ describe('mergeProfilesForDiffing with source tables', function () {
     sharedB.sourceLocationTable.column.push(44);
     sharedB.sourceLocationTable.length = 1;
     sharedB.funcTable.originalLocation[0] = 0;
+    sharedB.funcTable.flags[0] |= FuncFlag.HasOriginalLocation;
     sharedB.frameTable.originalLocation[0] = 0;
+    sharedB.frameTable.flags[0] |= FrameFlag.HasOriginalLocation;
 
     const profileState = stateFromLocation({
       pathname: '/public/fakehash1/',
@@ -1098,10 +1102,14 @@ describe('mergeProfilesForDiffing with source tables', function () {
     expect(funcAIndex).toBeGreaterThanOrEqual(0);
     expect(funcBIndex).toBeGreaterThanOrEqual(0);
 
+    expect(funcTable.flags[funcAIndex] & FuncFlag.HasOriginalLocation).not.toBe(
+      0
+    );
+    expect(funcTable.flags[funcBIndex] & FuncFlag.HasOriginalLocation).not.toBe(
+      0
+    );
     const funcAOriginalLocationIdx = funcTable.originalLocation[funcAIndex];
     const funcBOriginalLocationIdx = funcTable.originalLocation[funcBIndex];
-    expect(funcAOriginalLocationIdx).not.toBeNull();
-    expect(funcBOriginalLocationIdx).not.toBeNull();
     expect(
       sourceLocationTable.line[ensureExists(funcAOriginalLocationIdx)]
     ).toBe(11);
@@ -1143,8 +1151,9 @@ describe('mergeProfilesForDiffing with source tables', function () {
     expect(sourceLocationTable.length).toBe(0);
     expect(funcTable.originalLocation).toHaveLength(funcTable.length);
     expect(frameTable.originalLocation).toHaveLength(frameTable.length);
-    for (const v of funcTable.originalLocation) {
-      expect(v).toBeNull();
+    // No HasOriginalLocation bits should be set on any func.
+    for (let i = 0; i < funcTable.length; i++) {
+      expect(funcTable.flags[i] & FuncFlag.HasOriginalLocation).toBe(0);
     }
     // On the frame table, no HasOriginalLocation bits should be set.
     for (let i = 0; i < frameTable.length; i++) {
diff --git a/src/test/unit/process-profile.test.ts b/src/test/unit/process-profile.test.ts
index ad6ec61389..71014b9934 100644
--- a/src/test/unit/process-profile.test.ts
+++ b/src/test/unit/process-profile.test.ts
@@ -39,7 +39,7 @@ import type {
   IndexIntoStackTable,
   GeckoSamples,
 } from 'firefox-profiler/types';
-import { FrameFlag } from 'firefox-profiler/types';
+import { FrameFlag, FuncFlag } from 'firefox-profiler/types';
 
 describe('extract functions and resource from location strings', function () {
   // These location strings are turned into the proper funcs.
@@ -133,17 +133,26 @@ describe('extract functions and resource from location strings', function () {
         const locationName = locations[locationIndex];
 
         const funcName = stringTable.getString(funcTable.name[funcIndex]);
-        const resourceIndex = funcTable.resource[funcIndex];
-        const isJS = funcTable.isJS[funcIndex];
-        const sourceIndex = funcTable.source[funcIndex];
-        const fileNameIndex =
-          sourceIndex !== null ? sources.filename[sourceIndex] : null;
+        const funcFlags = funcTable.flags[funcIndex];
+        const hasResource = (funcFlags & FuncFlag.HasResource) !== 0;
+        const resourceIndex = hasResource ? funcTable.resource[funcIndex] : -1;
+        const isJS = (funcFlags & FuncFlag.IsJS) !== 0;
+        const hasSource = (funcFlags & FuncFlag.HasSource) !== 0;
+        const fileNameIndex = hasSource
+          ? sources.filename[funcTable.source[funcIndex]]
+          : null;
         const fileName =
           fileNameIndex === null ? null : stringTable.getString(fileNameIndex);
-        const lineNumber = funcTable.lineNumber[funcIndex];
-        const columnNumber = funcTable.columnNumber[funcIndex];
+        const lineNumber =
+          (funcFlags & FuncFlag.HasLine) !== 0
+            ? funcTable.lineNumber[funcIndex]
+            : null;
+        const columnNumber =
+          (funcFlags & FuncFlag.HasColumn) !== 0
+            ? funcTable.columnNumber[funcIndex]
+            : null;
         let resourceName, host, resourceType;
-        if (resourceIndex === -1) {
+        if (!hasResource) {
           resourceName = null;
           host = null;
           resourceType = null;
diff --git a/src/test/unit/profile-data.test.ts b/src/test/unit/profile-data.test.ts
index a3423b1a21..4d17eb69d8 100644
--- a/src/test/unit/profile-data.test.ts
+++ b/src/test/unit/profile-data.test.ts
@@ -65,7 +65,12 @@ import type {
   IndexIntoCategoryList,
   IndexIntoNativeSymbolTable,
 } from 'firefox-profiler/types';
-import { SelectedState, ResourceType, FrameFlag } from 'firefox-profiler/types';
+import {
+  SelectedState,
+  ResourceType,
+  FrameFlag,
+  FuncFlag,
+} from 'firefox-profiler/types';
 
 describe('string-table', function () {
   const u = StringTable.withBackingArray(['foo', 'bar', 'baz']);
@@ -290,7 +295,8 @@ describe('process-profile', function () {
       expect(shared.frameTable.address[22]).toEqual(0x1a45);
       expect(shared.frameTable.address[24]).toEqual(0xf84);
       expect(shared.frameTable.address[25]).toEqual(0xf84);
-      const funcTableNames = shared.funcTable.name.map(
+      const funcTableNames = Array.from(
+        shared.funcTable.name,
         (nameIndex) => shared.stringArray[nameIndex]
       );
       expect(funcTableNames[0]).toEqual('(root)');
@@ -895,7 +901,7 @@ describe('filter-by-implementation', function () {
     }
     const frameIndex = filteredThread.stackTable.frame[stackIndex];
     const funcIndex = filteredThread.frameTable.func[frameIndex];
-    return filteredThread.funcTable.isJS[funcIndex];
+    return (filteredThread.funcTable.flags[funcIndex] & FuncFlag.IsJS) !== 0;
   }
 
   it('will return the same thread if filtering to "all"', function () {
diff --git a/src/test/unit/profile-tree.test.ts b/src/test/unit/profile-tree.test.ts
index 93e2c75f4c..48c82e95e1 100644
--- a/src/test/unit/profile-tree.test.ts
+++ b/src/test/unit/profile-tree.test.ts
@@ -14,6 +14,7 @@ import {
 import { computeFlameGraphRows } from '../../profile-logic/flame-graph';
 import {
   computeFrameTableFromRawFrameTable,
+  computeFuncTableFromRawFuncTable,
   getCallNodeInfo,
   getInvertedCallNodeInfo,
   getOriginAnnotationForFunc,
@@ -21,7 +22,7 @@ import {
   filterRawThreadSamplesToRange,
   getSampleIndexToCallNodeIndex,
 } from '../../profile-logic/profile-data';
-import { ResourceType, FrameFlag } from 'firefox-profiler/types';
+import { ResourceType, FrameFlag, FuncFlag } from 'firefox-profiler/types';
 import {
   callTreeFromProfile,
   functionListTreeFromProfile,
@@ -694,9 +695,14 @@ describe('origin annotation', function () {
     const resourceIndex = shared.resourceTable.length;
     const funcIndex = funcNames.indexOf(funcName);
     shared.funcTable.resource[funcIndex] = resourceIndex;
-    shared.funcTable.source[funcIndex] = location
-      ? addSourceToTable(shared.sources, stringTable.indexForString(location))
-      : null;
+    shared.funcTable.flags[funcIndex] |= FuncFlag.HasResource;
+    if (location) {
+      shared.funcTable.source[funcIndex] = addSourceToTable(
+        shared.sources,
+        stringTable.indexForString(location)
+      );
+      shared.funcTable.flags[funcIndex] |= FuncFlag.HasSource;
+    }
     shared.resourceTable.name.push(stringTable.indexForString(name));
     shared.resourceTable.host.push(
       host ? stringTable.indexForString(host) : null
@@ -727,7 +733,7 @@ describe('origin annotation', function () {
       funcNames.indexOf(funcName),
       null,
       computeFrameTableFromRawFrameTable(shared.frameTable, undefined),
-      shared.funcTable,
+      computeFuncTableFromRawFuncTable(shared.funcTable),
       shared.resourceTable,
       stringTable,
       shared.sources
@@ -771,6 +777,8 @@ describe('getOriginAnnotationForFunc with originalLocation', function () {
     shared.funcTable.source[0] = bundleIndex;
     shared.funcTable.lineNumber[0] = 1;
     shared.funcTable.columnNumber[0] = 100;
+    shared.funcTable.flags[0] |=
+      FuncFlag.HasSource | FuncFlag.HasLine | FuncFlag.HasColumn;
 
     // The text sample produces one frame referencing func 0. Give it a
     // compiled position so tier-3 fallback has something meaningful to surface.
@@ -803,7 +811,7 @@ describe('getOriginAnnotationForFunc with originalLocation', function () {
         0,
         0,
         computeFrameTableFromRawFrameTable(shared.frameTable, undefined),
-        shared.funcTable,
+        computeFuncTableFromRawFuncTable(shared.funcTable),
         shared.resourceTable,
         stringTable,
         shared.sources,
@@ -834,6 +842,7 @@ describe('getOriginAnnotationForFunc with originalLocation', function () {
       10,
       4
     );
+    shared.funcTable.flags[0] |= FuncFlag.HasOriginalLocation;
     expect(callOrigin(null)).toEqual('http://example.com/original.ts:10:4');
   });
 
@@ -860,6 +869,8 @@ describe('getOriginalPositionForFrame', function () {
     shared.funcTable.source[0] = bundleIndex;
     shared.funcTable.lineNumber[0] = 1;
     shared.funcTable.columnNumber[0] = 100;
+    shared.funcTable.flags[0] |=
+      FuncFlag.HasSource | FuncFlag.HasLine | FuncFlag.HasColumn;
     shared.frameTable.flags[0] |= FrameFlag.HasLine | FrameFlag.HasColumn;
     shared.frameTable.line[0] = 5;
     shared.frameTable.column[0] = 10;
@@ -893,7 +904,7 @@ describe('getOriginalPositionForFrame', function () {
         0,
         0,
         computeFrameTableFromRawFrameTable(shared.frameTable, undefined),
-        shared.funcTable,
+        computeFuncTableFromRawFuncTable(shared.funcTable),
         shared.sourceLocationTable
       )
     ).toEqual({ source: originalIndex, line: 42, column: 7 });
@@ -906,12 +917,13 @@ describe('getOriginalPositionForFrame', function () {
       10,
       4
     );
+    shared.funcTable.flags[0] |= FuncFlag.HasOriginalLocation;
     expect(
       getOriginalPositionForFrame(
         0,
         0,
         computeFrameTableFromRawFrameTable(shared.frameTable, undefined),
-        shared.funcTable,
+        computeFuncTableFromRawFuncTable(shared.funcTable),
         shared.sourceLocationTable
       )
     ).toEqual({ source: originalIndex, line: 10, column: 4 });
@@ -924,7 +936,7 @@ describe('getOriginalPositionForFrame', function () {
         0,
         0,
         computeFrameTableFromRawFrameTable(shared.frameTable, undefined),
-        shared.funcTable,
+        computeFuncTableFromRawFuncTable(shared.funcTable),
         shared.sourceLocationTable
       )
     ).toEqual({ source: bundleIndex, line: 5, column: 10 });
@@ -940,7 +952,7 @@ describe('getOriginalPositionForFrame', function () {
         0,
         0,
         computeFrameTableFromRawFrameTable(shared.frameTable, undefined),
-        shared.funcTable,
+        computeFuncTableFromRawFuncTable(shared.funcTable),
         shared.sourceLocationTable
       )
     ).toEqual({ source: bundleIndex, line: 1, column: 100 });
@@ -953,12 +965,13 @@ describe('getOriginalPositionForFrame', function () {
       10,
       4
     );
+    shared.funcTable.flags[0] |= FuncFlag.HasOriginalLocation;
     expect(
       getOriginalPositionForFrame(
         null,
         0,
         computeFrameTableFromRawFrameTable(shared.frameTable, undefined),
-        shared.funcTable,
+        computeFuncTableFromRawFuncTable(shared.funcTable),
         shared.sourceLocationTable
       )
     ).toEqual({ source: originalIndex, line: 10, column: 4 });
@@ -972,12 +985,13 @@ describe('getOriginalPositionForFrame', function () {
       10,
       4
     );
+    shared.funcTable.flags[0] |= FuncFlag.HasOriginalLocation;
     expect(
       getOriginalPositionForFrame(
         0,
         0,
         computeFrameTableFromRawFrameTable(shared.frameTable, undefined),
-        shared.funcTable,
+        computeFuncTableFromRawFuncTable(shared.funcTable),
         null
       )
     ).toEqual({ source: bundleIndex, line: 5, column: 10 });
diff --git a/src/test/url-handling.test.ts b/src/test/url-handling.test.ts
index 044983ca6d..72e1a1f257 100644
--- a/src/test/url-handling.test.ts
+++ b/src/test/url-handling.test.ts
@@ -44,6 +44,7 @@ import type {
   IndexIntoSourceTable,
   BottomBoxInfo,
 } from 'firefox-profiler/types';
+import { FuncFlag } from 'firefox-profiler/types';
 import getNiceProfile from './fixtures/profiles/call-nodes';
 import queryString from 'query-string';
 import {
@@ -915,9 +916,8 @@ describe('url upgrading', function () {
         G.js
       `);
 
-      profile.shared.funcTable.relevantForJS[
-        funcNamesDictPerThread.DrelevantForJs
-      ] = true;
+      profile.shared.funcTable.flags[funcNamesDictPerThread.DrelevantForJs] |=
+        FuncFlag.RelevantForJS;
 
       const callNodePathBefore = [
         funcNamesDictPerThread['B.js'],
@@ -967,9 +967,8 @@ describe('url upgrading', function () {
         E.js
       `);
 
-      profile.shared.funcTable.relevantForJS[
-        funcNamesDictPerThread.BrelevantForJs
-      ] = true;
+      profile.shared.funcTable.flags[funcNamesDictPerThread.BrelevantForJs] |=
+        FuncFlag.RelevantForJS;
 
       const callNodePathBefore = [
         funcNamesDictPerThread['C.js'],
@@ -1018,9 +1017,8 @@ describe('url upgrading', function () {
         F.js
       `);
 
-      profile.shared.funcTable.relevantForJS[
-        funcNamesDictPerThread.BrelevantForJs
-      ] = true;
+      profile.shared.funcTable.flags[funcNamesDictPerThread.BrelevantForJs] |=
+        FuncFlag.RelevantForJS;
 
       const callNodePathBefore = [
         funcNamesDictPerThread['D.js'],
@@ -1068,9 +1066,8 @@ describe('url upgrading', function () {
         G.js            E.js
       `);
 
-      profile.shared.funcTable.relevantForJS[
-        funcNamesDictPerThread.CrelevantForJs
-      ] = true;
+      profile.shared.funcTable.flags[funcNamesDictPerThread.CrelevantForJs] |=
+        FuncFlag.RelevantForJS;
 
       const callNodePathBefore = [
         funcNamesDictPerThread['B.js'],
@@ -1118,9 +1115,8 @@ describe('url upgrading', function () {
         G.js            E.js
       `);
 
-      profile.shared.funcTable.relevantForJS[
-        funcNamesDictPerThread.BrelevantForJs
-      ] = true;
+      profile.shared.funcTable.flags[funcNamesDictPerThread.BrelevantForJs] |=
+        FuncFlag.RelevantForJS;
 
       const callNodePathBefore = [
         funcNamesDictPerThread['C.js'],
diff --git a/src/types/actions.ts b/src/types/actions.ts
index 888a3b05a9..01d57310b3 100644
--- a/src/types/actions.ts
+++ b/src/types/actions.ts
@@ -13,7 +13,7 @@ import type {
   IndexIntoCategoryList,
   PageList,
   IndexIntoSourceTable,
-  FuncTable,
+  RawFuncTable,
   RawFrameTable,
   SourceLocationTable,
   SourceTable,
@@ -456,7 +456,7 @@ type ReceiveProfileAction =
   | { readonly type: 'SOURCE_MAP_SYMBOLICATION_FAILED' }
   | {
       readonly type: 'BULK_SOURCE_MAP_SYMBOLICATION';
-      readonly newFuncTable: FuncTable;
+      readonly newFuncTable: RawFuncTable;
       readonly newFrameTable: RawFrameTable;
       readonly newSourceLocationTable: SourceLocationTable;
       readonly newSources: SourceTable;
diff --git a/src/types/profile-derived.ts b/src/types/profile-derived.ts
index fb74792a12..b93f55826d 100644
--- a/src/types/profile-derived.ts
+++ b/src/types/profile-derived.ts
@@ -20,7 +20,6 @@ import type {
   ProcessType,
   PausedRange,
   RawMarkerTable,
-  FuncTable,
   ResourceTable,
   JsTracerTable,
   IndexIntoStackTable,
@@ -305,6 +304,27 @@ export type FrameTable = {
   length: number;
 };
 
+/**
+ * The `FuncTable` type of the derived thread.
+ *
+ * Differs from `RawFuncTable` in that all columns are always stored as typed
+ * arrays. In `RawFuncTable`, these columns may be either regular arrays or
+ * typed arrays, since regular arrays are convenient during construction.
+ *
+ * See the comment on `RawFuncTable` for the semantics of the `flags` column
+ * and how it relates to the other columns.
+ */
+export type FuncTable = {
+  flags: Uint8Array<ArrayBuffer>;
+  name: Int32Array<ArrayBuffer>;
+  resource: Int32Array<ArrayBuffer>;
+  source: Int32Array<ArrayBuffer>;
+  lineNumber: Int32Array<ArrayBuffer>;
+  columnNumber: Int32Array<ArrayBuffer>;
+  originalLocation: Int32Array<ArrayBuffer>;
+  length: number;
+};
+
 /**
  * The `NativeSymbolTable` type of the derived thread.
  *
diff --git a/src/types/profile.ts b/src/types/profile.ts
index 6414dc43f0..8337046d64 100644
--- a/src/types/profile.ts
+++ b/src/types/profile.ts
@@ -398,36 +398,69 @@ export type RawFrameTable = {
  * were created upfront to become orphaned, as the frames that originally referred
  * to them get reassigned to the canonical func for their actual function.
  */
-export type FuncTable = {
-  // The function name.
-  name: Array<IndexIntoStringTable>;
+/**
+ * Bit flags for the `flags` column of the RawFuncTable / FuncTable.
+ * Each flag indicates whether the corresponding column carries a meaningful
+ * value for that func; when a flag bit is unset, the value in the associated
+ * column is ignored.
+ */
+export const FuncFlag = {
+  // Set when this func is a JavaScript function.
+  IsJS: 1 << 0,
+  // Set when this func should be treated as "relevant for JS" (e.g. DOM API
+  // label funcs). Non-JavaScript functions can be marked as "relevant for JS"
+  // so that they show up in JavaScript stack views. IsJS implies RelevantForJS
+  // in practice but the bit is stored explicitly.
+  RelevantForJS: 1 << 1,
+  // Set when `resource` is meaningful (i.e. this func has an associated
+  // resource, not the sentinel).
+  HasResource: 1 << 2,
+  // Set when `source` is meaningful (this func has an associated source file).
+  HasSource: 1 << 3,
+  // Set when `lineNumber` is meaningful.
+  HasLine: 1 << 4,
+  // Set when `columnNumber` is meaningful.
+  HasColumn: 1 << 5,
+  // Set when `originalLocation` is meaningful.
+  HasOriginalLocation: 1 << 6,
+} as const;
+
+export type FuncFlags = number;
+
+export type RawFuncTable = {
+  // A bitfield with one bit per optional column, drawn from `FuncFlag`.
+  // For each row, the flag bit tells you whether the value in the
+  // corresponding column is meaningful. When a bit is unset, the value in the
+  // corresponding column has no meaning; producers can store any value there
+  // (typically 0) and consumers must ignore it.
+  flags: number[] | Uint8Array<ArrayBuffer>;
 
-  // isJS and relevantForJS describe the function type. Non-JavaScript functions
-  // can be marked as "relevant for JS" so that for example DOM API label functions
-  // will show up in any JavaScript stack views.
-  // It may be worth combining these two fields into one:
-  // https://github.com/firefox-devtools/profiler/issues/2543
-  isJS: Array<boolean>;
-  relevantForJS: Array<boolean>;
+  // The function name.
+  name: Array<IndexIntoStringTable> | Int32Array<ArrayBuffer>;
 
   // The resource describes "Which bag of code did this function come from?".
   // For JS functions, the resource is of type addon, webhost, otherhost, or url.
   // For native functions, the resource is of type library.
-  // For labels and for other unidentified functions, we set the resource to -1.
-  resource: Array<IndexIntoResourceTable | -1>;
+  // Only meaningful when `HasResource` is set in `flags`.
+  resource: Array<IndexIntoResourceTable> | Int32Array<ArrayBuffer>;
 
   // These are non-null for JS functions only. The line and column describe the
   // location of the *start* of the JS function. As for the information about which
   // which lines / columns inside the function were actually hit during execution,
   // that information is stored in the frameTable, not in the funcTable.
-  source: Array<IndexIntoSourceTable | null>;
-  lineNumber: Array<number | null>;
-  columnNumber: Array<number | null>;
+  // Only meaningful when `HasSource` is set.
+  source: Array<IndexIntoSourceTable> | Int32Array<ArrayBuffer>;
+  // Only meaningful when `HasLine` is set.
+  lineNumber: Array<number> | Int32Array<ArrayBuffer>;
+  // Only meaningful when `HasColumn` is set.
+  columnNumber: Array<number> | Int32Array<ArrayBuffer>;
 
-  // Index into the sourceLocationTable, or null if not source-mapped.
-  // Points to the original source file, line, and column for this function's
-  // definition.
-  originalLocation: Array<IndexIntoSourceLocationTable | null>;
+  // Index into the sourceLocationTable, pointing at the original source file,
+  // line, and column for this function's definition. Only meaningful when
+  // `HasOriginalLocation` is set.
+  originalLocation:
+    | Array<IndexIntoSourceLocationTable>
+    | Int32Array<ArrayBuffer>;
 
   length: number;
 };
@@ -1153,7 +1186,7 @@ export type SourceLocationTable = {
 export type RawProfileSharedData = {
   stackTable: RawStackTable;
   frameTable: RawFrameTable;
-  funcTable: FuncTable;
+  funcTable: RawFuncTable;
   resourceTable: ResourceTable;
   nativeSymbols: RawNativeSymbolTable;
   // Strings for profiles are collected into a single table, and are referred to by