[EXPERIMENT] Test 8-bit tags for hashbrown

[Amanieu]

See rust-lang/hashbrown#653

[Amanieu]

@bors try @rust-timer queue

[Amanieu]

@bors try cancel

[rust-bors]

Try build cancelled. Cancelled workflows:

• https://github.com/rust-lang/rust/actions/runs/17927565095

[Amanieu]

@bors try

[rust-log-analyzer]

The job aarch64-gnu-llvm-20-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[TIMING:start] compile::Std { target: aarch64-unknown-linux-gnu, build_compiler: Compiler { stage: 1, host: aarch64-unknown-linux-gnu, forced_compiler: false }, crates: [], force_recompile: false, extra_rust_args: [], is_for_mir_opt_tests: false }
[TIMING:start] compile::StartupObjects { compiler: Compiler { stage: 1, host: aarch64-unknown-linux-gnu, forced_compiler: false }, target: aarch64-unknown-linux-gnu }
[TIMING:end] compile::StartupObjects { compiler: Compiler { stage: 1, host: aarch64-unknown-linux-gnu, forced_compiler: false }, target: aarch64-unknown-linux-gnu } -- 0.000
##[group]Building stage1 library artifacts (stage1 -> stage1, aarch64-unknown-linux-gnu)
    Updating git repository `https://github.com/gaujay/hashbrown.git`
    Updating crates.io index
---
   Compiling rustc-std-workspace-alloc v1.99.0 (/checkout/library/rustc-std-workspace-alloc)
   Compiling panic_unwind v0.0.0 (/checkout/library/panic_unwind)
   Compiling gimli v0.32.0
[RUSTC-TIMING] rustc_std_workspace_alloc test:false 0.031
   Compiling hashbrown v0.16.0 (https://github.com/gaujay/hashbrown.git?branch=8-bits-tag#fcce0699)
[RUSTC-TIMING] panic_unwind test:false 0.100
error[E0308]: mismatched types
     --> /cargo/git/checkouts/hashbrown-19ea029273e5a732/fcce069/src/control/group/neon.rs:72:61
      |
   72 |             let cmp = neon::vceq_u8(self.0, neon::vdup_n_u8(tag.0));
      |                                             --------------- ^^^^^ expected `u8`, found `i8`
      |                                             |
      |                                             arguments to this function are incorrect
      |
note: function defined here
     --> /checkout/library/core/src/../../stdarch/crates/core_arch/src/arm_shared/neon/generated.rs:10793:8
      |
10793 | pub fn vdup_n_u8(value: u8) -> uint8x8_t {
      |        ^^^^^^^^^
help: you can convert an `i8` to a `u8` and panic if the converted value doesn't fit
      |
   72 |             let cmp = neon::vceq_u8(self.0, neon::vdup_n_u8(tag.0.try_into().unwrap()));
      |                                                                  ++++++++++++++++++++

error[E0308]: mismatched types
    --> /cargo/git/checkouts/hashbrown-19ea029273e5a732/fcce069/src/raw/mod.rs:1707:40
     |
1707 |             for bit in group.match_tag(tag_hash) {
     |                              --------- ^^^^^^^^ expected `Tag`, found `i32`
     |                              |
     |                              arguments to this method are incorrect
     |
note: method defined here
    --> /cargo/git/checkouts/hashbrown-19ea029273e5a732/fcce069/src/control/group/neon.rs:70:19
     |
  70 |     pub(crate) fn match_tag(self, tag: Tag) -> BitMask {
     |                   ^^^^^^^^^       --------

error[E0308]: mismatched types
    --> /cargo/git/checkouts/hashbrown-19ea029273e5a732/fcce069/src/raw/mod.rs:1916:40
     |
1916 |             for bit in group.match_tag(tag_hash) {
     |                              --------- ^^^^^^^^ expected `Tag`, found `i32`
     |                              |
     |                              arguments to this method are incorrect
     |
note: method defined here
    --> /cargo/git/checkouts/hashbrown-19ea029273e5a732/fcce069/src/control/group/neon.rs:70:19
     |
  70 |     pub(crate) fn match_tag(self, tag: Tag) -> BitMask {
     |                   ^^^^^^^^^       --------

error[E0308]: mismatched types
    --> /cargo/git/checkouts/hashbrown-19ea029273e5a732/fcce069/src/raw/mod.rs:4085:39
     |
4085 |         let bitmask = group.match_tag(tag_hash).into_iter();
     |                             --------- ^^^^^^^^ expected `Tag`, found `i32`
     |                             |
     |                             arguments to this method are incorrect
     |
note: method defined here
    --> /cargo/git/checkouts/hashbrown-19ea029273e5a732/fcce069/src/control/group/neon.rs:70:19
     |
  70 |     pub(crate) fn match_tag(self, tag: Tag) -> BitMask {
     |                   ^^^^^^^^^       --------

error[E0308]: mismatched types
    --> /cargo/git/checkouts/hashbrown-19ea029273e5a732/fcce069/src/raw/mod.rs:4139:53
     |
4139 |                 self.bitmask = self.group.match_tag(self.tag_hash).into_iter();
     |                                           --------- ^^^^^^^^^^^^^ expected `Tag`, found `i32`
     |                                           |
     |                                           arguments to this method are incorrect
     |
note: method defined here
    --> /cargo/git/checkouts/hashbrown-19ea029273e5a732/fcce069/src/control/group/neon.rs:70:19
     |
  70 |     pub(crate) fn match_tag(self, tag: Tag) -> BitMask {
     |                   ^^^^^^^^^       --------

[RUSTC-TIMING] alloc test:false 6.295
   Compiling std_detect v0.1.5 (/checkout/library/std_detect)
For more information about this error, try `rustc --explain E0308`.

[rust-bors]

☀️ Try build successful (CI)
Build commit: d29dae6 (d29dae6c92b168ee50770c080643f888f6b5cd62, parent: ce4beebecb77821734079cff47d8af08f9f27f11)

[rust-timer]

Finished benchmarking commit (d29dae6): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.3%	[0.1%, 1.1%]	82
Regressions ❌ (secondary)	0.3%	[0.1%, 1.1%]	78
Improvements ✅ (primary)	-1.2%	[-1.7%, -0.8%]	2
Improvements ✅ (secondary)	-0.2%	[-0.3%, -0.1%]	3
All ❌✅ (primary)	0.2%	[-1.7%, 1.1%]	84

Max RSS (memory usage)

Results (primary 2.4%, secondary 0.9%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	3.9%	[2.5%, 6.7%]	3
Regressions ❌ (secondary)	2.5%	[1.2%, 3.8%]	2
Improvements ✅ (primary)	-2.0%	[-2.0%, -2.0%]	1
Improvements ✅ (secondary)	-2.5%	[-2.5%, -2.5%]	1
All ❌✅ (primary)	2.4%	[-2.0%, 6.7%]	4

Cycles

Results (primary 1.9%, secondary 2.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.9%	[1.9%, 1.9%]	1
Regressions ❌ (secondary)	2.2%	[1.7%, 2.6%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.9%	[1.9%, 1.9%]	1

Binary size

Results (primary 0.1%, secondary 0.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.0%, 0.8%]	45
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	3
Improvements ✅ (primary)	-0.3%	[-0.9%, -0.1%]	7
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.3%]	1
All ❌✅ (primary)	0.1%	[-0.9%, 0.8%]	52

Bootstrap: 472.191s -> 472.724s (0.11%)
Artifact size: 389.95 MiB -> 390.24 MiB (0.07%)

[bors]

☔ The latest upstream changes (presumably #149159) made this pull request unmergeable. Please resolve the merge conflicts.