generator layout: ignore fake borrows #117712

lcnr · 2023-11-08T13:13:25Z

We emit fake shallow borrows in case the scrutinee place uses a Deref and there is a match guard. This is necessary to prevent the match guard from mutating the scrutinee:

rust/compiler/rustc_mir_build/src/build/matches/mod.rs

Lines 1250 to 1265 in fab1054

    
           // Insert a borrows of prefixes of places that are bound and are 
        
           // behind a dereference projection. 
        
           // 
        
           // These borrows are taken to avoid situations like the following: 
        
           // 
        
           // match x[10] { 
        
           //     _ if { x = &[0]; false } => (), 
        
           //     y => (), // Out of bounds array access! 
        
           // } 
        
           // 
        
           // match *x { 
        
           //     // y is bound by reference in the guard and then by copy in the 
        
           //     // arm, so y is 2 in the arm! 
        
           //     y if { y == 1 && (x = &2) == () } => y, 
        
           //     _ => 3, 
        
           // }

These fake borrows end up impacting the generator witness computation in mir_generator_witnesses, which causes the issue in #117059. This PR now completely ignores fake borrows during this computation. This is sound as thse are always removed after analysis and the actual computation of the generator layout happens afterwards.

Only the second commit impacts behavior, and could be backported by itself.

r? types

rustbot · 2023-11-08T13:13:37Z

This PR changes MIR

cc @oli-obk, @RalfJung, @JakobDegen, @davidtwco, @celinval, @vakaras

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

This PR changes Stable MIR

cc @oli-obk, @celinval, @spastorino, @ouz-a

BoxyUwU · 2023-11-08T13:21:12Z

r? types

lcnr · 2023-11-08T13:25:38Z

Going to use a t-types fcp again, merging once the FCP period starts without waiting for 10 days.

@rfcbot fcp merge

rfcbot · 2023-11-08T13:25:40Z

Team member @lcnr has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

jackh726 · 2023-11-08T13:33:29Z

r=me when FCP completes

also adds some comments

lcnr · 2023-11-09T09:00:08Z

(checked the box for @oli-obk as they're currently not available)

aliemjay · 2023-11-09T10:29:04Z

@rfcbot reviewed

rfcbot · 2023-11-09T10:29:10Z

🔔 This is now entering its final comment period, as per the review above. 🔔

lcnr · 2023-11-09T10:46:13Z

@bors r=jackh726 p=1

generator layout: ignore fake borrows fixes rust-lang#117059 We emit fake shallow borrows in case the scrutinee place uses a `Deref` and there is a match guard. This is necessary to prevent the match guard from mutating the scrutinee: https://github.com/rust-lang/rust/blob/fab1054e1742790c22ccc92a625736d658363677/compiler/rustc_mir_build/src/build/matches/mod.rs#L1250-L1265 These fake borrows end up impacting the generator witness computation in `mir_generator_witnesses`, which causes the issue in rust-lang#117059. This PR now completely ignores fake borrows during this computation. This is sound as thse are always removed after analysis and the actual computation of the generator layout happens afterwards. Only the second commit impacts behavior, and could be backported by itself. r? types

apiraino · 2023-11-09T11:12:17Z

Beta backport accepted as per compiler team on Zulip

@rustbot label +beta-accepted

wesleywiser · 2023-11-09T11:15:44Z

It is possible to only backport the second commit (after fixing the comment here which belongs in the next commit). However, T-compiler is fine with taking the whole PR as the rest of the rest of the changes are mechanical in nature.

rust-log-analyzer · 2023-11-09T12:24:50Z

The job x86_64-apple-1 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

SCCACHE_BUCKET=rust-lang-ci-sccache2
SCRIPT=./x.py --stage 2 test --skip tests/ui --skip tests/rustdoc --skip tests/run-make-fulldeps
SHELL=/bin/bash
SHLVL=3
SSH_AUTH_SOCK=/private/tmp/com.apple.launchd.A9bQDgyjTu/Listeners
STATS_EXT=true
STATS_EXTP=https://provjobdsettingscdn.blob.core.windows.net/settings/provjobdsettings-0.5.154/provjobd.data
STATS_RDCL=true
STATS_TIS=mining

bors · 2023-11-09T12:25:17Z

💔 Test failed - checks-actions

lcnr · 2023-11-09T12:33:15Z

@bors retry

seems spurious

bors · 2023-11-09T14:23:49Z

⌛ Testing commit 92267c9 with merge b7583d3...

bors · 2023-11-09T16:23:13Z

☀️ Test successful - checks-actions
Approved by: jackh726
Pushing b7583d3 to master...

rust-timer · 2023-11-09T20:00:59Z

Finished benchmarking commit (b7583d3): 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)	-0.4%	[-0.4%, -0.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	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)	0.6%	[0.4%, 0.9%]	7
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.6%	[-0.7%, -0.5%]	4
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[-0.7%, 0.9%]	11

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)	-0.4%	[-0.5%, -0.4%]	2
Improvements ✅ (secondary)	-13.6%	[-13.8%, -13.4%]	2
All ❌✅ (primary)	-0.4%	[-0.5%, -0.4%]	2

Binary size

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

Bootstrap: 663.537s -> 662.476s (-0.16%)
Artifact size: 308.81 MiB -> 308.77 MiB (-0.01%)

[beta] backports - dropck_outlives check whether generator witness needs_drop rust-lang#117134 - Make sure that predicates with unmentioned bound vars are still considered global in the old solver rust-lang#117589 - Check binders with bound vars for global bounds that don't hold rust-lang#117637 - generator layout: ignore fake borrows rust-lang#117712 r? ghost

Update Rust toolchain from nightly-2023-11-09 to nightly-2023-11-10 without any other source changes. This is an automatically generated pull request. If any of the CI checks fail, manual intervention is required. In such a case, review the changes at https://github.com/rust-lang/rust from rust-lang@fdaaaf9 up to rust-lang@0f44eb3. The log for this commit range is: rust-lang@0f44eb32f1 Auto merge of rust-lang#117727 - saethlin:inline-derived-fmt, r=nnethercote rust-lang@eae4135939 Auto merge of rust-lang#117708 - onur-ozkan:x-setup, r=clubby789 rust-lang@4c8862b263 Auto merge of rust-lang#117122 - ferrocene:pa-configure-git-diff, r=albertlarsan68 rust-lang@d32d9238cf Emit #[inline] on derive(Debug) rust-lang@b7583d38b7 Auto merge of rust-lang#117712 - lcnr:expand-coroutine, r=jackh726 rust-lang@488dd9bc73 fmt rust-lang@e7998aa21f Auto merge of rust-lang#117734 - nnethercote:rm-Zstrip, r=davidtwco rust-lang@287ae4db75 Auto merge of rust-lang#117632 - Nilstrieb:icup, r=davidtwco rust-lang@492e57c6ad Auto merge of rust-lang#117736 - TaKO8Ki:rollup-fjrtmlb, r=TaKO8Ki rust-lang@d1e26401bc chore(bootstrap): capitalize {error, warning, info, note} tags rust-lang@42fbf3ebf5 allow users to override the existing configuration during x setup rust-lang@3d6417fc7a check config file before prompts on x setup rust-lang@f5195c52bb Rollup merge of rust-lang#117724 - Kobzol:shim-error-message, r=onur-ozkan rust-lang@e603f4491c Rollup merge of rust-lang#117723 - onur-ozkan:keep-bootstrap-on-x-clean, r=albertlarsan68 rust-lang@6533c62ce7 Rollup merge of rust-lang#117705 - tshepang:patch-2, r=Nilstrieb rust-lang@b4fa5b7004 Rollup merge of rust-lang#117694 - jmillikin:core-io-borrowed-buf, r=m-ou-se rust-lang@4cc549811f Rollup merge of rust-lang#117645 - compiler-errors:auto-trait-subst, r=petrochenkov rust-lang@a1a8d6fe9c Rollup merge of rust-lang#116762 - WaffleLapkin:fixup_fromptr_docs, r=RalfJung rust-lang@d8dbf7ca0e Auto merge of rust-lang#117557 - Zoxc:panic-prio, r=petrochenkov rust-lang@ecc936b155 Remove `-Z strip`. rust-lang@57fb1e643a Auto merge of rust-lang#117454 - shepmaster:github-actions-m1-tests, r=GuillaumeGomez,onur-ozkan rust-lang@341c85648c Move `BorrowedBuf` and `BorrowedCursor` from `std:io` to `core::io` rust-lang@92267c9794 update mir-opt tests rust-lang@992d93f687 rename `BorrowKind::Shallow` to `Fake` rust-lang@a42eca42df generator layout: ignore fake borrows rust-lang@622be2d138 Restore rustc shim error message rust-lang@de0458af97 speed up `x clean` rust-lang@6909992501 Run tests in CI for aarch64-apple-darwin rust-lang@64090536d4 Install tidy for aarch64-apple-darwin rust-lang@469d34b39b Mark Rustdoc test as Linux-only rust-lang@bf360d407e instrument constituent types computation rust-lang@03435e6fdd accept review suggestion rust-lang@769ad29c3e triagebot.toml: use inclusive language rust-lang@102384523a Document how rust atomics work wrt mixed-sized and non-atomic accesses rust-lang@c17d33f1df Extend builtin/auto trait args with error when they have >1 argument rust-lang@580fa0c1a9 rename github_repository to git_repository rust-lang@ffffc2038f Update ICU4X rust-lang@ff1858e2aa Make `FatalErrorMarker` lower priority than other panics rust-lang@4a0873533f update suggest-tests rust-lang@5a562d962e pass the correct args to compiletest rust-lang@545cc830e1 allow configuring the parent GitHub repository Co-authored-by: celinval <celinval@users.noreply.github.com>

instrument constituent types computation

bf360d4

rustbot assigned BoxyUwU Nov 8, 2023

lcnr added the beta-nominated Nominated for backporting to the compiler in the beta channel. label Nov 8, 2023

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. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Nov 8, 2023

lcnr added the I-types-nominated Nominated for discussion during a types team meeting. label Nov 8, 2023

rustbot added the T-types Relevant to the types team, which will review and decide on the PR/issue. label Nov 8, 2023

rustbot assigned jackh726 and unassigned BoxyUwU Nov 8, 2023

lcnr removed the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Nov 8, 2023

rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Nov 8, 2023

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lcnr added 3 commits November 8, 2023 22:55

generator layout: ignore fake borrows

a42eca4

rename BorrowKind::Shallow to Fake

992d93f

also adds some comments

update mir-opt tests

92267c9

lcnr force-pushed the expand-coroutine branch from dbb2914 to 92267c9 Compare November 8, 2023 21:55

rfcbot added the final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. label Nov 9, 2023

rfcbot removed the proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. label Nov 9, 2023

rustbot added the beta-accepted Accepted for backporting to the compiler in the beta channel. label Nov 9, 2023

bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Nov 9, 2023

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 9, 2023

bors added the merged-by-bors This PR was explicitly merged by bors. label Nov 9, 2023

bors merged commit b7583d3 into rust-lang:master Nov 9, 2023
11 checks passed

rustbot added this to the 1.75.0 milestone Nov 9, 2023

bors mentioned this pull request Nov 9, 2023

static mut: allow mutable reference to arbitrary types, not just slices and arrays #117614

Merged

cuviper mentioned this pull request Nov 9, 2023

[beta] backports #117764

Merged

cuviper modified the milestones: 1.75.0, 1.74.0 Nov 9, 2023

cuviper removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Nov 9, 2023

lcnr deleted the expand-coroutine branch November 9, 2023 22:36

apiraino removed the to-announce Announce this issue on triage meeting label Dec 14, 2023

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generator layout: ignore fake borrows #117712

generator layout: ignore fake borrows #117712

lcnr commented Nov 8, 2023 •

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rust-timer commented Nov 9, 2023

	// Insert a borrows of prefixes of places that are bound and are
	// behind a dereference projection.
	//
	// These borrows are taken to avoid situations like the following:
	//
	// match x[10] {
	// _ if { x = &[0]; false } => (),
	// y => (), // Out of bounds array access!
	// }
	//
	// match *x {
	// // y is bound by reference in the guard and then by copy in the
	// // arm, so y is 2 in the arm!
	// y if { y == 1 && (x = &2) == () } => y,
	// _ => 3,
	// }

generator layout: ignore fake borrows #117712

generator layout: ignore fake borrows #117712

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rust-timer commented Nov 9, 2023

Overall result: ✅ improvements - no action needed

Instruction count

Max RSS (memory usage)

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Binary size

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