Don't use Immediate::offset to transmute pointers to integers

[RalfJung]

This applies the relatively new assert_matches_abi check in the offset operation on immediates, which makes sure that if offsets are used to alter the layout (which is possible because the field layout is arbitrarily picked by the caller), this is not done in a way that breaks the invariant of the Immediate type.

This leads to ICEs in a GVN mir-opt test, so the second commit fixes GVN.

Fixes #131064.

[rustbot]

r? @chenyukang

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[rustbot]

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

[bors]

☔ The latest upstream changes (presumably #131006) made this pull request unmergeable. Please resolve the merge conflicts.

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[RalfJung]

This is unblocked now, I added a second commit that fixes the ICE.

Cc @cjgillot

[rustbot]

Some changes occurred in coverage tests.

cc @Zalathar

[RalfJung]

This changes something in the coverage output. I don't know what that output means or why it changes now, but if it relied on bogus optimizations then it's probably better to have it fixed now...

[Zalathar]

Looks like an artifact of some MIR node no longer being optimized away.

As you say, if a bogus optimization is no longer happening, then that's probably for the best.

[chenyukang]

r? compiler

[nnethercote]

Is it worth adding a debug_assert_matches_abi method?

[RalfJung]

IMO no, I'd rather not duplicate this logic.

[nnethercote]

Wouldn't it look like this, with no logic duplication?

pub fn debug_assert_matches_abi(self, abi: Abi, cx: &impl HasDataLayout) {
    if cfg!(debug_assertions) {
        self.assert_matches_abi(abi, cx);
    }
}

[RalfJung]

Ah, that's what you mean.

Didn't seem worth it to me. 🤷

[nnethercote]

@bors r+

[bors]

📌 Commit 7d63efd has been approved by nnethercote

It is now in the queue for this repository.

[bors]

⌛ Testing commit 7d63efd with merge a964a92...

[bors]

☀️ Test successful - checks-actions
Approved by: nnethercote
Pushing a964a92 to master...

[rust-timer]

Finished benchmarking commit (a964a92): comparison URL.

Overall result: ❌ regressions - 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)	0.2%	[0.2%, 0.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

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)	2.1%	[2.0%, 2.1%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.1%	[2.0%, 2.1%]	2

Cycles

Results (secondary -0.5%)

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)	6.4%	[2.3%, 9.2%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-7.5%	[-8.8%, -6.8%]	6
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 774.632s -> 773.837s (-0.10%)
Artifact size: 329.53 MiB -> 329.55 MiB (0.01%)