ci: Download and cache LLVM for the fuzz build

Author: tgross35

.github/workflows/main.yaml

@@ -22,9 +22,18 @@ jobs:
             os: ubuntu-24.04
     steps:
     - uses: actions/checkout@v6
-    - name: Install Rust
-      run: rustup update nightly --no-self-update && rustup default nightly
+    - name: Install Dependencies
+      run: |
+        rustup update nightly --no-self-update
+        rustup default nightly
+        sudo apt-get install -y llvm  # Needed to build the C++ APFloat
+    - name: Download llvm source
+      run: ./etc/download-llvm.sh
+    # This should also cache LLVM since it downloads to `target/llvm-downloads`
     - uses: Swatinem/rust-cache@v2
+      with:
+        key: ${{ matrix.target }}
+
     - name: Build and run tests
       run: cargo test --workspace
 
@@ -48,7 +57,7 @@ jobs:
     - uses: Swatinem/rust-cache@v2
     - run: |
         # strip the fuzz crate that uses a newer edition
-        sed '/members =/d' Cargo.toml
+        sed -i '/members =/d' Cargo.toml
         cargo build --package rustc_apfloat
 
   rustfmt:

etc/download-llvm.sh

@@ -12,8 +12,13 @@ version="$(
 llvm_hash="${version##*-}"
 
 target_dir="${CARGO_TARGET_DIR:-target}"
-out_dir="$target_dir/llvm-downloads/"
+out_dir="$target_dir/llvm-downloads"
 mkdir -p "$out_dir"
 
+if [ -d "$out_dir/llvm-project-$llvm_hash" ] && [ "${1:-}" != "-f" ]; then
+    echo Download already exists. Pass '-f' to overwrite.
+    exit
+fi
+
 tgz_url="https://codeload.github.com/llvm/llvm-project/tar.gz/$llvm_hash"
 curl -sS "$tgz_url" | tar -C "$out_dir" -xz

fuzz/src/apf_fuzz.cpp

@@ -127,7 +127,7 @@ class FloatEval {
                 rm = APFloat::rmNearestTiesToAway;
                 break;
             default:
-                printf("unsupported rounding mode %d\n", rm);
+                printf("unsupported rounding mode %d\n", static_cast<int8_t>(rm));
                 exit(1);
         }
 
@@ -175,7 +175,7 @@ class FloatEval {
                 a.convert(sem, rm, &cvt_exact);
                 break;
             default:
-                printf("unrecognized op tag %d", tag);
+                printf("unrecognized op tag %d", static_cast<int8_t>(tag));
                 exit(1);
         }