valtree performance tuning

[lukas-code]

Summary: This PR makes type checking of code with many type-level constants faster.

After #136180 was merged, we observed a small perf regression (#136318 (comment)). This happened because that PR introduced additional copies in the fast reject code path for consts, which is very hot for certain crates:

rust/compiler/rustc_type_ir/src/fast_reject.rs

Lines 486 to 487 in 6c1d960

	ty::ConstKind::Value(lhs_val) => match rhs.kind() {
	ty::ConstKind::Value(rhs_val) => lhs_val.valtree() == rhs_val.valtree(),

This PR improves the performance again by properly interning the valtrees so that copying and comparing them becomes faster. This will become especially useful with feature(adt_const_params), so the fast reject code doesn't have to do a deep compare of the valtrees.

A less invasive alternative that I considered is simply avoiding copies introduced by #136180 and comparing the valtrees it in-place (see commit: 9e91e50 / perf results: #136593 (comment)), however that was still measurably slower than interning.

[lukas-code]

@bors try @rust-timer queue

[bors]

⌛ Trying commit dc8caa3 with merge 95bc439...

[bors]

☀️ Try build successful - checks-actions
Build commit: 95bc439 (95bc439e0cc5e28a3a245d530f8acb3b84d250ac)

[rust-timer]

Finished benchmarking commit (95bc439): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

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

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary -2.0%, secondary -1.1%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	6.3%	[6.3%, 6.3%]	1
Improvements ✅ (primary)	-2.0%	[-2.0%, -2.0%]	1
Improvements ✅ (secondary)	-3.5%	[-3.8%, -3.4%]	3
All ❌✅ (primary)	-2.0%	[-2.0%, -2.0%]	1

Cycles

Results (secondary 2.5%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.5%	[2.5%, 2.5%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 778.541s -> 779.446s (0.12%)
Artifact size: 328.82 MiB -> 328.84 MiB (0.01%)

[lukas-code]

@bors try @rust-timer queue

[bors]

⌛ Trying commit bc51bb2 with merge 9e91e50...

[bors]

☀️ Try build successful - checks-actions
Build commit: 9e91e50 (9e91e50ac5920f0b9b4a3b1e0880c85336ba5c64)

[rust-timer]

Finished benchmarking commit (9e91e50): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

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

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.6%	[-2.6%, -0.1%]	14
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.3%]	1
All ❌✅ (primary)	-1.6%	[-2.6%, -0.1%]	14

Max RSS (memory usage)

Results (primary -0.9%, secondary -2.5%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.1%	[1.1%, 1.1%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.0%	[-3.0%, -3.0%]	1
Improvements ✅ (secondary)	-2.5%	[-2.5%, -2.5%]	1
All ❌✅ (primary)	-0.9%	[-3.0%, 1.1%]	2

Cycles

Results (primary -2.1%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.1%	[-3.0%, -1.6%]	9
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.1%	[-3.0%, -1.6%]	9

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 780.473s -> 782.144s (0.21%)
Artifact size: 329.02 MiB -> 328.96 MiB (-0.02%)

[lukas-code]

@bors try @rust-timer queue

[bors]

⌛ Trying commit cd733ad with merge b50e910...

[lukas-code]

@rust-timer build b50e910

[rust-timer]

Error occurred while parsing comment: Invalid command argument b50e910b6edc6d2acb791008b59627f355c12932 (there may be no spaces around the = character)

[rust-timer]

Finished benchmarking commit (b50e910): comparison URL.

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

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

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

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	2.7%	[2.7%, 2.7%]	1
Regressions ❌ (secondary)	0.3%	[0.2%, 0.6%]	7
Improvements ✅ (primary)	-2.5%	[-5.6%, -0.2%]	21
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.2%	[-5.6%, 2.7%]	22

Max RSS (memory usage)

Results (secondary 1.8%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.5%	[2.2%, 4.9%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.7%	[-1.7%, -1.7%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (primary -2.8%, secondary 2.3%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	2.5%	[2.5%, 2.5%]	1
Regressions ❌ (secondary)	2.3%	[2.3%, 2.3%]	1
Improvements ✅ (primary)	-3.2%	[-5.4%, -2.2%]	16
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.8%	[-5.4%, 2.5%]	17

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 779.143s -> 777.841s (-0.17%)
Artifact size: 329.04 MiB -> 328.98 MiB (-0.02%)

[bors]

☔ The latest upstream changes (presumably #136762) made this pull request unmergeable. Please resolve the merge conflicts.

[lukas-code]

@bors try @rust-timer queue

[bors]

⌛ Trying commit d6f5175 with merge fdc99c9...

[bors]

☀️ Try build successful - checks-actions
Build commit: fdc99c9 (fdc99c910e177780043e910ad8466f227059293f)

[rust-timer]

Finished benchmarking commit (fdc99c9): comparison URL.

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

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

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

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.4%	[0.2%, 0.5%]	5
Improvements ✅ (primary)	-2.7%	[-5.7%, -0.2%]	20
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	1
All ❌✅ (primary)	-2.7%	[-5.7%, -0.2%]	20

Max RSS (memory usage)

Results (primary -1.2%, secondary 2.3%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.5%	[4.5%, 4.5%]	2
Improvements ✅ (primary)	-1.2%	[-1.2%, -1.2%]	1
Improvements ✅ (secondary)	-2.1%	[-2.1%, -2.1%]	1
All ❌✅ (primary)	-1.2%	[-1.2%, -1.2%]	1

Cycles

Results (primary -3.1%, secondary 2.7%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.7%	[2.3%, 3.1%]	2
Improvements ✅ (primary)	-3.1%	[-6.1%, -1.9%]	19
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-3.1%	[-6.1%, -1.9%]	19

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 779.273s -> 777.952s (-0.17%)
Artifact size: 329.09 MiB -> 329.05 MiB (-0.01%)