Separate const prop lints from optimizations

[Lireer]

r? @oli-obk

Separates lints and optimizations during const prop by moving the lints into their own file and checking them during post borrowck cleanup.
Thanks to @oli-obk for mentoring me.

[oli-obk]

If you write fixes #70073 merging this PR will automatically close that issue

[oli-obk]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit 449f1e18d211f9c0018d6f79cf1c02bb8110e776 with merge 11e53ca50fce06dbb1fa00ab5a78ee351b427888...

[Lireer]

Some issues that might be affected by this PR #81265, #82646, #81224, #70923, #51491.

[tmiasko]

run_post_borrowck_cleanup_passes doesn't run for --emit metadata / cargo check, except for const fns. You might want to experiment with changing that as well:

rust/compiler/rustc_interface/src/passes.rs

Lines 976 to 979 in bce19cf

	if tcx.hir().body_const_context(def_id).is_some() {
	tcx.ensure()
	.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(def_id));
	}

[tmiasko]

@rust-timer build 11e53ca50fce06dbb1fa00ab5a78ee351b427888

[rust-timer]

Queued 11e53ca50fce06dbb1fa00ab5a78ee351b427888 with parent 0ac4658, future comparison URL.

[oli-obk]

run_post_borrowck_cleanup_passes doesn't run for --emit metadata / cargo check, except for const fns. You might want to experiment with changing that as well:

rust/compiler/rustc_interface/src/passes.rs

Lines 976 to 979 in bce19cf

	if tcx.hir().body_const_context(def_id).is_some() {
	tcx.ensure()
	.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(def_id));
	}

We could also try moving the lint even earlier. mir-interpret should be able to handle it with some minor tweaks to change panics into more benign failures

Edit: will address this in follow up PRs

[rust-timer]

Finished benchmarking commit (11e53ca50fce06dbb1fa00ab5a78ee351b427888): comparison url.

Summary: This benchmark run shows 56 relevant regressions 😿 to instruction counts.

• Arithmetic mean of relevant regressions: 1.0%
• Largest regression in instruction counts: 2.0% on incr-patched: println builds of unicode_normalization debug

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

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 led to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression

[oli-obk]

We're doing const prop twice now, so it's fairly obvious where the regression is coming from. This is expected, since the current PR is the first step to fix the bug that optimizations can change diagnostics.

[oli-obk]

@bors r+ rollup=never

[bors]

📌 Commit da1a68326927f815a72347368352e2fa01c48e30 has been approved by oli-obk

[bors]

⌛ Testing commit da1a68326927f815a72347368352e2fa01c48e30 with merge 4976c2337559584555ca2e9567413e85218a0ad3...

[bors]

💔 Test failed - checks-actions

[bors]

☔ The latest upstream changes (presumably #95056) made this pull request unmergeable. Please resolve the merge conflicts.

[oli-obk]

@bors r+

[bors]

💡 This pull request was already approved, no need to approve it again.

• This pull request previously failed. You should add more commits to fix the bug, or use retry to trigger a build again.
• There's another pull request that is currently being tested, blocking this pull request: Properly track ImplObligations #91030

[bors]

📌 Commit 440946a has been approved by oli-obk

[bors]

⌛ Testing commit 440946a with merge 903707951703c815ca0bf6432bdce20e0873acda...

[rust-log-analyzer]

A job failed! Check out the build log: (web) (plain)

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

[bors]

💔 Test failed - checks-actions

[oli-obk]

@bors retry failure near submodule checkouts

[bors]

⌛ Testing commit 440946a with merge 63b8f01...

[bors]

☀️ Test successful - checks-actions
Approved by: oli-obk
Pushing 63b8f01 to master...

[rust-timer]

Finished benchmarking commit (63b8f01): comparison url.

Summary: This benchmark run shows 40 relevant regressions 😿 to instruction counts.

• Arithmetic mean of relevant regressions: 1.2%
• Largest regression in instruction counts: 2.1% on incr-full builds of unicode_normalization opt

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression

[oli-obk]

We're doing const prop twice now, so it's fairly obvious where the regression is coming from. This is expected, since the current PR is the first step to fix the bug that optimizations can change diagnostics.

@rustbot label: +perf-regression-triaged