Rename `UninhabitedEnumBranching` to `UnreachableEnumBranching` #122225

DianQK · 2024-03-09T07:06:58Z

Per #120268, I rename UninhabitedEnumBranching to UnreachableEnumBranching .

I solved some nits to add some comments.

I adjusted the workaround restrictions. This should be useful for a <= b and if let Some/Ok(v). For enum with few variants, early-tailduplication should not cause compile time overhead.

r? RalfJung

rustbot · 2024-03-09T07:07:07Z

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

RalfJung · 2024-03-09T11:29:13Z

Thanks for the PR! However, unfortunately I can't review any behavior change in a MIR opt, nor can I tell whether the new tests make sense.
r? compiler

cjgillot · 2024-03-09T18:42:31Z

@bors try @rust-timer queue

bors · 2024-03-09T18:43:40Z

⌛ Trying commit 2b156ba with merge ba9e2ee...

Rename `UninhabitedEnumBranching` to `UnreachableEnumBranching` Per [rust-lang#120268](rust-lang#120268 (comment)), I rename `UninhabitedEnumBranching` to `UnreachableEnumBranching` . I solved some nits to add some comments. I adjusted the workaround restrictions. This should be useful for `a <= b` and `if let Some/Ok(v)`. For enum with few variants, `early-tailduplication` should not cause compile time overhead. r? RalfJung

bors · 2024-03-09T20:13:05Z

☀️ Try build successful - checks-actions
Build commit: ba9e2ee (ba9e2eebdf0a51a604ce7a9697acbbff9a354bb1)

rust-timer · 2024-03-09T23:20:07Z

Finished benchmarking commit (ba9e2ee): 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
Regressions ❌ (secondary)	0.3%	[0.3%, 0.3%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
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)	2.5%	[0.2%, 3.8%]	5
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-9.6%	[-12.0%, -7.2%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.9%	[-12.0%, 3.8%]	7

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)	0.9%	[0.9%, 0.9%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.9%	[0.9%, 0.9%]	1

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)	0.1%	[0.1%, 0.1%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.0%	[-0.1%, -0.0%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[-0.1%, 0.1%]	5

Bootstrap: 650.585s -> 649.35s (-0.19%)
Artifact size: 310.34 MiB -> 310.38 MiB (0.01%)

DianQK · 2024-03-11T02:43:18Z

@cjgillot Would you be willing to add yourself to mir-opt in triagebot.toml. Then I can use r? mir-opt. :)

riking · 2024-03-12T17:04:44Z

compiler/rustc_mir_transform/src/unreachable_enum_branching.rs

            let replace_otherwise_to_unreachable = otherwise_is_last_variant
-                || !otherwise_is_empty_unreachable && allowed_variants.is_empty();
+                || (!otherwise_is_empty_unreachable && allowed_variants.is_empty());

            if unreachable_targets.is_empty() && !replace_otherwise_to_unreachable {
                continue;


The allow(rustc::potential_query_instability) should include a comment that the length of the list is known to be 1. Or use one of the exactly_one iterator adapaters.

…` or `Result` `early-tailduplication` is only a problem when there are a significant number of branches.

cjgillot · 2024-04-03T00:27:16Z

@bors r+

bors · 2024-04-03T00:27:19Z

📌 Commit ec313d1 has been approved by cjgillot

It is now in the queue for this repository.

bors · 2024-04-03T06:22:27Z

⌛ Testing commit ec313d1 with merge 76cf07d...

bors · 2024-04-03T08:27:41Z

☀️ Test successful - checks-actions
Approved by: cjgillot
Pushing 76cf07d to master...

rust-timer · 2024-04-03T09:43:51Z

Finished benchmarking commit (76cf07d): 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)	-0.3%	[-0.3%, -0.3%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.3%	[-0.3%, -0.3%]	1

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)	6.0%	[4.8%, 7.0%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.0%	[-3.8%, -0.2%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.8%	[-3.8%, 7.0%]	5

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)	2.1%	[2.1%, 2.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

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)	0.2%	[0.0%, 0.3%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.3%, -0.0%]	9
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.1%	[-0.3%, 0.3%]	12

Bootstrap: 667.614s -> 668.678s (0.16%)
Artifact size: 318.09 MiB -> 318.11 MiB (0.00%)

Rename UninhabitedEnumBranching to UnreachableEnumBranching

8ddd966

rustbot assigned RalfJung Mar 9, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Mar 9, 2024

rustbot assigned compiler-errors and unassigned RalfJung Mar 9, 2024

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Mar 9, 2024

cjgillot self-assigned this Mar 10, 2024

riking reviewed Mar 12, 2024

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compiler-errors removed their assignment Mar 12, 2024

DianQK added 5 commits March 13, 2024 22:35

Add comments for UnreachableEnumBranching

df33e02

Addition of parentheses to clarify precedence

a10d157

Update unreachable_enum_default_branch.rs

f8656ef

Remove restrictions on small enum statements such as Order, `Option…

102bda4

…` or `Result` `early-tailduplication` is only a problem when there are a significant number of branches.

Update the test case for SimplifyCfg-after-unreachable-enum-branching

ec313d1

DianQK force-pushed the nits-120268 branch from 2b156ba to ec313d1 Compare March 13, 2024 14:35

bors removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 3, 2024

bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Apr 3, 2024

bors added the merged-by-bors This PR was explicitly merged by bors. label Apr 3, 2024

bors merged commit 76cf07d into rust-lang:master Apr 3, 2024
12 checks passed

rustbot added this to the 1.79.0 milestone Apr 3, 2024

DianQK deleted the nits-120268 branch April 3, 2024 08:31

This was referenced Apr 3, 2024

Stabilize min_exhaustive_patterns #122792

Merged

Run InstSimplify before UnreachablePropagation #123256

Closed

DianQK mentioned this pull request Apr 7, 2024

Re-enable the early otherwise branch optimization #122387

Merged

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Rename `UninhabitedEnumBranching` to `UnreachableEnumBranching` #122225

Rename `UninhabitedEnumBranching` to `UnreachableEnumBranching` #122225

DianQK commented Mar 9, 2024

rustbot commented Mar 9, 2024

RalfJung commented Mar 9, 2024 •

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DianQK commented Mar 11, 2024

riking Mar 12, 2024 •

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rust-timer commented Apr 3, 2024

Rename UninhabitedEnumBranching to UnreachableEnumBranching #122225

Rename UninhabitedEnumBranching to UnreachableEnumBranching #122225

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rust-timer commented Mar 9, 2024

Overall result: ❌ regressions - no action needed

DianQK commented Mar 11, 2024

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cjgillot commented Apr 3, 2024

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rust-timer commented Apr 3, 2024

Overall result: ✅ improvements - no action needed

Rename `UninhabitedEnumBranching` to `UnreachableEnumBranching` #122225

Rename `UninhabitedEnumBranching` to `UnreachableEnumBranching` #122225

RalfJung commented Mar 9, 2024 •

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riking Mar 12, 2024 •

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