Computing crate_hash from metadata encoding instead of HIR (implements #94878) (very draft) by Daniel-B-Smith · Pull Request #154724 · rust-lang/rust

Daniel-B-Smith · 2026-04-02T18:15:01Z

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 · 2026-04-09T23:26:03Z

@bors try @rust-timer queue

rust-timer · 2026-04-28T22:11:38Z

Finished benchmarking commit (34256d3): 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)	0.5%	[0.2%, 1.0%]	46
Regressions ❌ (secondary)	0.9%	[0.1%, 3.9%]	31
Improvements ✅ (primary)	-0.6%	[-5.4%, -0.2%]	13
Improvements ✅ (secondary)	-0.4%	[-1.6%, -0.0%]	18
All ❌✅ (primary)	0.3%	[-5.4%, 1.0%]	59

Max RSS (memory usage)

Results (primary 0.5%, secondary -1.0%)

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

	mean	range	count
Regressions ❌ (primary)	5.6%	[5.6%, 5.6%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-4.5%	[-4.5%, -4.5%]	1
Improvements ✅ (secondary)	-1.0%	[-1.0%, -1.0%]	1
All ❌✅ (primary)	0.5%	[-4.5%, 5.6%]	2

Cycles

Results (primary -2.6%, secondary 3.0%)

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

	mean	range	count
Regressions ❌ (primary)	2.2%	[2.2%, 2.2%]	1
Regressions ❌ (secondary)	3.8%	[2.5%, 4.8%]	5
Improvements ✅ (primary)	-7.3%	[-7.3%, -7.3%]	1
Improvements ✅ (secondary)	-1.3%	[-1.3%, -1.3%]	1
All ❌✅ (primary)	-2.6%	[-7.3%, 2.2%]	2

Binary size

Results (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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	1
All ❌✅ (primary)	-	-	0

Bootstrap: 487.089s -> 487.591s (0.10%)
Artifact size: 393.44 MiB -> 393.40 MiB (-0.01%)

ZuseZ4 · 2026-05-01T00:38:43Z

@bors try @rust-timer queue

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

Daniel-B-Smith · 2026-05-01T00:39:56Z

Before the next perf numbers come back, there are two optimizations this time. First, I removed a few inputs into the crate_hash for the tcx.needs_crate_hash() && !tcx.needs_metadata() case. I also changed the hashing of the metadata bytes to be a straight stable hash of the byte stream instead of using a stable hashing context.

rust-bors · 2026-05-01T02:46:25Z

☀️ Try build successful (CI)
Build commit: d73a833 (d73a8336e43c291c192ed07d1d4c5f82597e3d86, parent: f53b654a8882fd5fc036c4ca7a4ff41ce32497a6)

rust-timer · 2026-05-01T03:26:48Z

Finished benchmarking commit (d73a833): 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)	0.6%	[0.2%, 1.0%]	47
Regressions ❌ (secondary)	0.8%	[0.1%, 3.7%]	30
Improvements ✅ (primary)	-0.7%	[-5.4%, -0.2%]	12
Improvements ✅ (secondary)	-0.4%	[-1.6%, -0.2%]	15
All ❌✅ (primary)	0.3%	[-5.4%, 1.0%]	59

Max RSS (memory usage)

Results (primary -3.4%, secondary 3.0%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.0%	[2.1%, 3.4%]	4
Improvements ✅ (primary)	-3.4%	[-4.4%, -2.5%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-3.4%	[-4.4%, -2.5%]	2

Cycles

Results (primary -6.5%, secondary 1.3%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.1%	[3.8%, 4.4%]	2
Improvements ✅ (primary)	-6.5%	[-6.5%, -6.5%]	1
Improvements ✅ (secondary)	-4.2%	[-4.2%, -4.2%]	1
All ❌✅ (primary)	-6.5%	[-6.5%, -6.5%]	1

Binary size

Results (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
Regressions ❌ (secondary)	0.1%	[0.1%, 0.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Bootstrap: 487.787s -> 499.567s (2.41%)
Artifact size: 390.97 MiB -> 390.94 MiB (-0.01%)

DO NOT SUBMIT!

Daniel-B-Smith · 2026-05-01T18:49:25Z

The next performance test is to see if removing the no_hash I added from the hir_crate would improve performance. That seems like the culprit of the IncrUnchanged regressions. I somewhat expect regressions in IncrPatched, but I don't know the relative magnitude of the two options.

JonathanBrouwer · 2026-05-01T20:56:54Z

@bors try @rust-timer queue

rust-timer · 2026-05-01T20:56:56Z

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

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

rust-bors · 2026-05-02T03:05:11Z

💔 Test for 9e15878 failed: CI

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Apr 2, 2026

This comment has been minimized.

Sign in to view

Daniel-B-Smith force-pushed the smithdb3/fix-94878 branch 5 times, most recently from 24c04d5 to c826667 Compare April 7, 2026 15:59

This comment has been minimized.

Sign in to view

Daniel-B-Smith force-pushed the smithdb3/fix-94878 branch from c826667 to 1fe48e6 Compare April 8, 2026 14:22

This comment has been minimized.

Sign in to view

Daniel-B-Smith force-pushed the smithdb3/fix-94878 branch 2 times, most recently from 43a7704 to 338aba3 Compare April 8, 2026 19:34

This comment has been minimized.

Sign in to view

Daniel-B-Smith force-pushed the smithdb3/fix-94878 branch 2 times, most recently from 0ddcd96 to d27cca5 Compare April 8, 2026 21:34

This comment has been minimized.

Sign in to view

Daniel-B-Smith force-pushed the smithdb3/fix-94878 branch 3 times, most recently from 1e5f269 to 4171895 Compare April 9, 2026 14:56

This comment has been minimized.

Sign in to view

Daniel-B-Smith changed the title ~~#94878~~ Computing crate_hash from metadata encoding instead of HIR (implements #94878) (very draft) Apr 9, 2026

This comment has been minimized.

Sign in to view

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 9, 2026

Daniel-B-Smith force-pushed the smithdb3/fix-94878 branch from 4171895 to bb57d62 Compare April 9, 2026 23:55

This comment has been minimized.

Sign in to view

Daniel-B-Smith force-pushed the smithdb3/fix-94878 branch from bb57d62 to 1ad9d87 Compare April 10, 2026 14:25

This comment has been minimized.

Sign in to view

rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 28, 2026

Daniel-B-Smith force-pushed the smithdb3/fix-94878 branch from ca61d35 to 05997b1 Compare April 30, 2026 21:09

This comment has been minimized.

Sign in to view

Daniel-B-Smith force-pushed the smithdb3/fix-94878 branch from 05997b1 to 4a7b9ef Compare April 30, 2026 23:34

This comment has been minimized.

Sign in to view

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label May 1, 2026

rust-bors Bot pushed a commit that referenced this pull request May 1, 2026

Auto merge of #154724 - Daniel-B-Smith:smithdb3/fix-94878, r=<try>

d73a833

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

This comment has been minimized.

Sign in to view

rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label May 1, 2026

Daniel-B-Smith added 6 commits May 1, 2026 14:46

Convert crate hash to use metadata instead of HIR

1555289

remove some HIR hashing

defdd7e

Comment out a currently failing test

97efc4b

DO NOT SUBMIT!

Checkpointing an attempted optimization

a90f748

Small optimization

de9fdcc

Restore HIR crate hashing

2f78a26

Daniel-B-Smith force-pushed the smithdb3/fix-94878 branch from 3662494 to 2f78a26 Compare May 1, 2026 20:02

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label May 1, 2026

This comment has been minimized.

Sign in to view

rust-bors Bot pushed a commit that referenced this pull request May 1, 2026

Auto merge of #154724 - Daniel-B-Smith:smithdb3/fix-94878, r=<try>

9e15878

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

Uh oh!

Conversation

Daniel-B-Smith commented Apr 2, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

nnethercote commented Apr 9, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

rust-timer commented Apr 28, 2026

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

Uh oh!

This comment has been minimized.

ZuseZ4 commented May 1, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

Daniel-B-Smith commented May 1, 2026

Uh oh!

rust-bors Bot commented May 1, 2026

Uh oh!

This comment has been minimized.

rust-timer commented May 1, 2026

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

Uh oh!

Daniel-B-Smith commented May 1, 2026

Uh oh!

JonathanBrouwer commented May 1, 2026

Uh oh!

rust-timer commented May 1, 2026

Uh oh!

This comment has been minimized.

rust-bors Bot commented May 2, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

10 participants

Daniel-B-Smith commented Apr 2, 2026 •

edited by rustbot

Loading