Computing crate_hash from metadata encoding instead of HIR (implements #94878) (very draft)

[Daniel-B-Smith]

Adds a parallel process of hashing along with the metadata encoding. It does add metadata encoding in a few places to ensure that the hash was available. Currently, the metadata encoding always generates both the metadata and the hash even if only one is needed.

Known issue: one test failure due to #137108 (pre-existing repr(simd) projection bug. The new metadata pass trips some MIR validation. This will need to catch the issue earlier.

Local profiling on laptop shows roughly neutral (~0.5%), requesting CI perf run for precise measurement

[nnethercote]

@bors try @rust-timer queue

[rust-log-analyzer]

The job aarch64-gnu-llvm-21-1 failed! Check out the build log: (web) (plain enhanced) (plain)

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

Executing "/scripts/stage_2_test_set1.sh"
+ /scripts/stage_2_test_set1.sh
PR_CI_JOB set; skipping tidy
+ '[' 1 == 1 ']'
+ echo 'PR_CI_JOB set; skipping tidy'
+ SKIP_TIDY='--skip tidy'
+ ../x.py --stage 2 test --skip tidy --skip compiler --skip src
##[group]Building bootstrap
    Finished `dev` profile [unoptimized] target(s) in 0.04s
##[endgroup]
downloading https://static.rust-lang.org/dist/2026-03-05/rustfmt-nightly-aarch64-unknown-linux-gnu.tar.xz
---
---- [ui] tests/ui/simd/shuffle.rs#opt stdout ----

error in revision `opt`: test compilation failed although it shouldn't!
status: exit status: 101
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/simd/shuffle.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--cfg" "opt" "--check-cfg" "cfg(test,FALSE,opt,noopt)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/simd/shuffle.opt/a" "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers" "-O"
stdout: none
--- stderr -------------------------------
##[error]error: internal compiler error: compiler/rustc_mir_transform/src/validate.rs:81:25: broken MIR in Item(DefId(0:43 ~ shuffle[8d15]::{impl#1}::clone)) (after phase change to runtime-optimized) at bb0[1]:
                                Projecting into SIMD type Simd is banned by MCP#838
  --> /checkout/tests/ui/simd/shuffle.rs:16:32
   |
LL | #[derive(Copy, Clone, ConstParamTy, PartialEq, Eq)]
   |                ----- in this derive macro expansion
LL | #[repr(simd)]
LL | struct Simd<T, const N: usize>([T; N]);
   |                                ^^^^^^


thread 'rustc' (151671) panicked at compiler/rustc_mir_transform/src/validate.rs:81:25:
Box<dyn Any>
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::diagnostic::BugAbort as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
   2: <rustc_errors::DiagCtxtHandle>::span_bug::<rustc_span::span_encoding::Span, alloc::string::String>
   3: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
   4: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
   5: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
   6: rustc_middle::util::bug::span_bug_fmt::<rustc_span::span_encoding::Span>
   7: <rustc_mir_transform::validate::CfgChecker>::fail::<alloc::string::String>
   8: <rustc_mir_transform::validate::Validator as rustc_mir_transform::pass_manager::MirPass>::run_pass
   9: rustc_mir_transform::pass_manager::run_passes_inner
  10: rustc_mir_transform::run_optimization_passes
  11: rustc_mir_transform::optimized_mir
      [... omitted 2 frames ...]
  12: rustc_mir_transform::deduce_param_attrs::deduced_param_attrs
      [... omitted 2 frames ...]
  13: <rustc_metadata::rmeta::encoder::EncodeContext>::encode_crate_root
  14: rustc_metadata::rmeta::encoder::encode_metadata::{closure#3}::{closure#0}
  15: <rustc_metadata::rmeta::encoder::encode_metadata::{closure#3} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, &std::path::Path)>>::call_once
  16: rustc_metadata::rmeta::encoder::encode_metadata
  17: rustc_metadata::fs::encode_and_write_metadata
  18: rustc_interface::passes::start_codegen
  19: <rustc_interface::queries::Linker>::codegen_and_build_linker
  20: <std::thread::local::LocalKey<core::cell::Cell<*const ()>>>::with::<rustc_middle::ty::context::tls::enter_context<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}, core::option::Option<rustc_interface::queries::Linker>>::{closure#1}, core::option::Option<rustc_interface::queries::Linker>>::{closure#0}, core::option::Option<rustc_interface::queries::Linker>>
  21: <rustc_middle::ty::context::TyCtxt>::create_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}>
  22: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>
  23: std::panicking::catch_unwind::<(), core::panic::unwind_safe::AssertUnwindSafe<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}::{closure#0}>>
  24: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
  25: rustc_span::create_session_globals_then::<(), rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}::{closure#0}>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

note: using internal features is not supported and expected to cause internal compiler errors when used incorrectly

note: rustc 1.96.0-nightly (74e25bba5 2026-04-10) running on aarch64-unknown-linux-gnu

note: compiler flags: -Z threads=1 -Z simulate-remapped-rust-src-base=/rustc/FAKE_PREFIX -Z translate-remapped-path-to-local-path=no -Z ignore-directory-in-diagnostics-source-blocks=/cargo -Z ignore-directory-in-diagnostics-source-blocks=/checkout/vendor -C codegen-units=1 -Z ui-testing -Z deduplicate-diagnostics=no -Z write-long-types-to-disk=no -C strip=debuginfo -C prefer-dynamic -C rpath -C debuginfo=0

query stack during panic:
#0 [optimized_mir] optimizing MIR for `<impl at /checkout/tests/ui/simd/shuffle.rs:14:16: 14:21>::clone`
#1 [deduced_param_attrs] deducing parameter attributes for <impl at /checkout/tests/ui/simd/shuffle.rs:14:16: 14:21>::clone
end of query stack
error: aborting due to 1 previous error
------------------------------------------

---- [ui] tests/ui/simd/shuffle.rs#opt stdout end ----

[nnethercote]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 78660b1 (78660b17cc996b4e0aef52dab0411773908ab93e, parent: 02c7f9bec0fd583160f8bcccb830216023b07bee)

[rust-timer]

Finished benchmarking commit (78660b1): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@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)	1.4%	[0.3%, 9.7%]	127
Regressions ❌ (secondary)	7.7%	[0.2%, 196.7%]	119
Improvements ✅ (primary)	-0.6%	[-5.2%, -0.2%]	27
Improvements ✅ (secondary)	-0.7%	[-2.0%, -0.3%]	20
All ❌✅ (primary)	1.1%	[-5.2%, 9.7%]	154

Max RSS (memory usage)

Results (primary 3.2%, secondary 19.7%)

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

	mean	range	count
Regressions ❌ (primary)	3.7%	[1.5%, 8.2%]	12
Regressions ❌ (secondary)	23.1%	[2.4%, 119.7%]	15
Improvements ✅ (primary)	-3.7%	[-3.7%, -3.7%]	1
Improvements ✅ (secondary)	-5.2%	[-5.4%, -4.9%]	2
All ❌✅ (primary)	3.2%	[-3.7%, 8.2%]	13

Cycles

Results (primary 5.0%, secondary 28.4%)

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

	mean	range	count
Regressions ❌ (primary)	5.8%	[1.5%, 12.5%]	14
Regressions ❌ (secondary)	29.7%	[2.5%, 197.4%]	25
Improvements ✅ (primary)	-6.7%	[-6.7%, -6.7%]	1
Improvements ✅ (secondary)	-3.0%	[-3.0%, -3.0%]	1
All ❌✅ (primary)	5.0%	[-6.7%, 12.5%]	15

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 491.759s -> 491.424s (-0.07%)
Artifact size: 394.19 MiB -> 394.26 MiB (0.02%)