[Experiment] Play with match lowering

[Nadrieril]

Match lowering to MIR has the reputation of being the most intricate piece of the compiler, and after banging my head on it for a bit I sure hope there isn't anything more intricate somewhere else. It's good quality code but I hope to unentangle it. This PR is me wrestling with it and asking rustc-timer for its opinion.

r? @ghost

[Nadrieril]

First off: after 4 years, can we remove this hack?

@bors try @rust-timer queue

[bors]

⌛ Trying commit 8ae0de2 with merge d0155dc...

[bors]

☀️ Try build successful - checks-actions
Build commit: d0155dc (d0155dcb4c205b18af0b9b3d50e809beeef5cd63)

[rust-timer]

Finished benchmarking commit (d0155dc): 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

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)	-1.4%	[-2.9%, -0.4%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.4%	[-2.9%, -0.4%]	3

Cycles

Results

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)	0.4%	[0.4%, 0.4%]	1
Regressions ❌ (secondary)	1.9%	[1.6%, 2.2%]	5
Improvements ✅ (primary)	-0.7%	[-1.0%, -0.4%]	2
Improvements ✅ (secondary)	-4.0%	[-4.0%, -4.0%]	1
All ❌✅ (primary)	-0.3%	[-1.0%, 0.4%]	3

Binary size

Results

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

Bootstrap: 672.726s -> 671.48s (-0.19%)
Artifact size: 312.44 MiB -> 312.48 MiB (0.01%)

[Nadrieril]

It seems we can! Popped this off: #119112

[Nadrieril]

I'll resuscitate this when I get back to it

[Nadrieril]

I eagerly simplify MatchPairs, let's see if perf likes that

@bors try @rust-timer queue

[bors]

⌛ Trying commit b005fea with merge 568ca85...

[bors]

💔 Test failed - checks-actions

[Nadrieril]

Well, looks like I messed up

[Nadrieril]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 6267474 with merge 625aff6...

[bors]

☀️ Try build successful - checks-actions
Build commit: 625aff6 (625aff67a4fe667136ce1c968d629814bb6f1753)

[rust-timer]

Finished benchmarking commit (625aff6): comparison URL.

Overall result: ❌ regressions - 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.

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 a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.7%	[0.5%, 0.8%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.7%	[0.5%, 0.8%]	3

Max RSS (memory usage)

Results

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)	6.6%	[6.6%, 6.6%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-3.7%, -1.1%]	2
All ❌✅ (primary)	6.6%	[6.6%, 6.6%]	1

Cycles

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

Binary size

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

Bootstrap: 652.672s -> 652.719s (0.01%)
Artifact size: 175.51 MiB -> 175.49 MiB (-0.01%)

[Nadrieril]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 6433f90 with merge c703bf4...

[bors]

☀️ Try build successful - checks-actions
Build commit: c703bf4 (c703bf4652fefce62ed4f36ac9d32716e113f3e7)

[rust-timer]

Finished benchmarking commit (c703bf4): comparison URL.

Overall result: ❌ regressions - 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 a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.7%	[0.5%, 0.8%]	2
Regressions ❌ (secondary)	0.4%	[0.4%, 0.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.7%	[0.5%, 0.8%]	2

Max RSS (memory usage)

Results

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)	2.9%	[2.9%, 2.9%]	2
Regressions ❌ (secondary)	3.9%	[2.7%, 5.1%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.7%	[-4.4%, -3.0%]	2
All ❌✅ (primary)	2.9%	[2.9%, 2.9%]	2

Cycles

Results

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)	3.7%	[3.6%, 3.8%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 652.82s -> 651.197s (-0.25%)
Artifact size: 175.51 MiB -> 175.52 MiB (0.01%)