Re-enable the early otherwise branch optimization

[DianQK]

Closes #95162. Fixes #119014.

This is the first part of #121397.

An invalid enum discriminant can come from anywhere. We have to check to see if all successors contain the discriminant statement. This should have a pass to hoist instructions.

r? cjgillot

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[bors]

☔ The latest upstream changes (presumably #122423) made this pull request unmergeable. Please resolve the merge conflicts.

[DianQK]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 57d566e with merge 1c207eb...

[bors]

☀️ Try build successful - checks-actions
Build commit: 1c207eb (1c207eb7b67fd11382d4e3cb46c8391d16a27f4d)

[rust-timer]

Finished benchmarking commit (1c207eb): 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 a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.4%	[-0.6%, -0.3%]	4
All ❌✅ (primary)	-	-	0

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)	-1.8%	[-4.9%, -0.8%]	13
Improvements ✅ (secondary)	-3.2%	[-4.8%, -2.0%]	37
All ❌✅ (primary)	-1.8%	[-4.9%, -0.8%]	13

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)	-	-	0
Improvements ✅ (primary)	-0.9%	[-1.0%, -0.8%]	4
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.9%	[-1.0%, -0.8%]	4

Binary size

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

Bootstrap: 670.407s -> 669.691s (-0.11%)
Artifact size: 315.71 MiB -> 315.69 MiB (-0.01%)

[cjgillot]

@bors r+

[bors]

📌 Commit 57d566e has been approved by cjgillot

It is now in the queue for this repository.

[DianQK]

Oops, I need to update the pass name to UnreachableEnumBranching after #122225.

@bors r-

[DianQK]

Done: https://github.com/rust-lang/rust/compare/6196373d842c467fe35d507608c67e415e9c8843..5428a15ff71acd951318d01f9df9cb85b24751a8.

[DianQK]

@rustbot ready

[cjgillot]

@bors r+

[bors]

📌 Commit 5428a15 has been approved by cjgillot

It is now in the queue for this repository.

[bors]

⌛ Testing commit 5428a15 with merge 7427e2c...

[bors]

💔 Test failed - checks-actions

[DianQK]

LLVM 17 cannot optimize it: https://godbolt.org/z/8d9PEoh9G. I have added @ min-llvm-version: 18.

[WaffleLapkin]

@bors r=cjgillot

[bors]

📌 Commit 166bb1b has been approved by cjgillot

It is now in the queue for this repository.

[bors]

⌛ Testing commit 166bb1b with merge 59c808f...

[bors]

☀️ Test successful - checks-actions
Approved by: cjgillot
Pushing 59c808f to master...

[rust-timer]

Finished benchmarking commit (59c808f): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.7%	[-0.7%, -0.7%]	1
All ❌✅ (primary)	-	-	0

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)	2.6%	[2.6%, 2.6%]	1
Regressions ❌ (secondary)	3.3%	[3.3%, 3.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.6%	[2.6%, 2.6%]	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: 674.046s -> 674.144s (0.01%)
Artifact size: 318.46 MiB -> 318.36 MiB (-0.03%)