Remove semi-nondeterminism of DefPathHash ordering from inliner

[compiler-errors]

Déjà vu or something because I kinda thought I had put this PR up before. I recall a discussion somewhere where I think it was @saethlin mentioning that this check was no longer needed since we have "proper" cycle detection. Putting that up as a PR now.

This may slighlty negatively affect inlining, since the cycle breaking here means that we still inlined some cycles when the def path hashes were ordered in certain ways, this leads to really bad nondeterminism that makes minimizing ICEs and putting up inliner bugfixes difficult.

r? @cjgillot or @saethlin or someone else idk

[compiler-errors]

@bors try @rust-timer queue

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[bors]

⌛ Trying commit 8f97231 with merge af813e4...

[saethlin]

I recall a discussion somewhere where I think it was @saethlin mentioning that this check was no longer needed since we have "proper" cycle detection.

I don't think I ever said that; the DefPathHash comparison has been in here the whole time I've worked on the code. But I similarly detest this property of the inliner. It doesn't just make minimizing ICEs difficult, it also makes our codegen globally unstable with respect to small edits of almost any kind.

[bors]

☀️ Try build successful - checks-actions
Build commit: af813e4 (af813e474e9257203839a37854187ce27c02daab)

[oli-obk]

Yea this was always fishy. The original inliner (even before I added cycle detection) already had this check to prevent cycle errors. Glad we have a principled way now

[rust-timer]

Finished benchmarking commit (af813e4): comparison URL.

Overall result: ❌ regressions - 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.

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-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)	0.9%	[0.4%, 2.6%]	5
Regressions ❌ (secondary)	0.5%	[0.1%, 0.8%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.9%	[0.4%, 2.6%]	5

Max RSS (memory usage)

Results (primary -2.8%)

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)	-2.8%	[-2.8%, -2.8%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.8%	[-2.8%, -2.8%]	2

Cycles

Results (primary 1.6%)

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)	1.6%	[1.6%, 1.6%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.6%	[1.6%, 1.6%]	1

Binary size

Results (primary 0.1%, secondary -0.2%)

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%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.4%, -0.0%]	2
All ❌✅ (primary)	0.1%	[0.1%, 0.1%]	1

Bootstrap: 760.616s -> 767.093s (0.85%)
Artifact size: 341.32 MiB -> 341.30 MiB (-0.01%)

[saethlin]

@rustbot label +perf-regression-triaged Acceptable overhead for being able to bisect inliner issues, or alternatively for a bugfix. See comments above.

@bors r+

[bors]

📌 Commit 8f97231 has been approved by saethlin

It is now in the queue for this repository.

[bors]

⌛ Testing commit 8f97231 with merge 46b0f8b...

[bors]

☀️ Test successful - checks-actions
Approved by: saethlin
Pushing 46b0f8b to master...

[rust-timer]

Finished benchmarking commit (46b0f8b): comparison URL.

Overall result: ❌ regressions - ACTION NEEDED

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
cc @rust-lang/wg-compiler-performance

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)	0.8%	[0.3%, 2.5%]	5
Regressions ❌ (secondary)	0.6%	[0.1%, 1.0%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.8%	[0.3%, 2.5%]	5

Max RSS (memory usage)

Results (primary 2.5%)

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)	2.5%	[2.5%, 2.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.5%	[2.5%, 2.5%]	1

Cycles

Results (primary 1.5%)

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)	1.5%	[1.5%, 1.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[1.5%, 1.5%]	1

Binary size

Results (primary 0.1%, secondary -0.2%)

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%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.4%, -0.0%]	2
All ❌✅ (primary)	0.1%	[0.1%, 0.1%]	1

Bootstrap: 759.624s -> 767.973s (1.10%)
Artifact size: 341.31 MiB -> 341.29 MiB (-0.01%)

[pnkfelix]

@rustbot label: +perf-regression-triaged

not sure why @saethlin 's attempt to do this above didn't work; do we strictly require the colon after the word "label" in the command?