Remove comments from mir-opt MIR dumps

[saethlin]

See https://rust-lang.zulipchat.com/#narrow/stream/189540-t-compiler.2Fwg-mir-opt/topic/Line.20numbers.20in.20mir-opt.20tests/near/363849874

In #99780 there is mention that "there has been a zulip conversation about disabling line numbers with mixed opinions" which to me means that some people opposed this. I can't find the referenced conversation so... here we go.

The current situation is quite chaotic. It's not hard to find MIR diffs which contain

• Absolute line numbers
• Relative line numbers
• Substituted line numbers (LL)
  For example:

  rust/tests/mir-opt/inline/inline_shims.drop.Inline.diff

  Lines 10 to 17 in 408bbd0

  	let mut _5: *mut std::option::Option<B>; // in scope 0 at $DIR/inline_shims.rs:+2:38: +2:39
  	scope 1 {
  	}
  	scope 2 {
  	+ scope 3 (inlined std::ptr::drop_in_place::<Option<B>> - shim(Some(Option<B>))) { // at $DIR/inline_shims.rs:12:14: 12:40
  	+ let mut _6: isize; // in scope 3 at $SRC_DIR/core/src/ptr/mod.rs:LL:COL
  	+ let mut _7: isize; // in scope 3 at $SRC_DIR/core/src/ptr/mod.rs:LL:COL
  	+ }

And sometimes adding a comment at the top of a mir-opt test generates a diff in the test because a line number changed: https://github.com/rust-lang/rust/pull/98112/files#diff-b8cf4bcce95078e6a3faf075e9abf6864872fb28a64d95c04f04513b9e3bbd81

And irrelevant changes to the standard library can generate diffs in mir-opt tests: https://github.com/rust-lang/rust/pull/110694/files#diff-bf96b0e7c67b8b272814536888fd9428c314991e155beae1f0a2a67f0ac47b2c
769886c

I think we should, specifically in mir-opt tests, completely remove the comments, or insert placeholders for all line and column numbers.

[rustbot]

r? @eholk

(rustbot has picked a reviewer for you, use r? to override)

[bjorn3]

Can you put the // mir::Constant on the same line as the _2 = const {alloc2: *mut i32};?

[saethlin]

Ah I see I missed a few more places the comments are emitted.

[saethlin]

r? mir-opt

[bors]

☔ The latest upstream changes (presumably #112418) made this pull request unmergeable. Please resolve the merge conflicts.

[oli-obk]

@bors r+ p=1 bitrotty

[bors]

📌 Commit e2fab8f0dcca015d83c83a06f5f25eb368b7bf5e has been approved by oli-obk

It is now in the queue for this repository.

[bors]

⌛ Testing commit e2fab8f0dcca015d83c83a06f5f25eb368b7bf5e with merge e72dff92be7b99d9222f4fdb685df5ca261c257a...

[bors]

💔 Test failed - checks-actions

[saethlin]

I goofed. I forgot that even with all the awesome improvements to blessing that @pietroalbini built, blessing with debug = true is still not effective.

[oli-obk]

@bors r+

[bors]

📌 Commit 0a1fa41 has been approved by oli-obk

It is now in the queue for this repository.

[scottmcm]

blessing with debug = true is still not effective.

Not this PR, but maybe emitting a warning for that could make sense?

(And I assume it's debug-std = true that's the major issue? debug = true; debug-std = false should be fine for blessing these?)

[saethlin]

The problem is that the tests don't get blessed at all because they are // ignore-debug.

Yes, it's the standard library code that's the problem, and I think this can be gracefully solved by piggybacking on the work Pietro did.

[bors]

⌛ Testing commit 0a1fa41 with merge c84d5e7...

[bors]

☀️ Test successful - checks-actions
Approved by: oli-obk
Pushing c84d5e7 to master...

[rust-timer]

Finished benchmarking commit (c84d5e7): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -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)	2.2%	[2.2%, 2.2%]	1
Improvements ✅ (primary)	-2.2%	[-2.2%, -2.2%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.2%	[-2.2%, -2.2%]	1

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)	3.4%	[1.1%, 4.5%]	6
Regressions ❌ (secondary)	1.4%	[1.4%, 1.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.4%	[1.1%, 4.5%]	6

Binary size

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

Bootstrap: 649.004s -> 647.175s (-0.28%)

[lqd]

It seems this PR removed comments from -Zdump-mir dumps that were not mir-opt tests. I'll open a PR.

[shepmaster]

This also removed functionality from the playground. I'll delete that code now.