Add cache-based fast path for cfgs and check-cfgs

[Urgau]

This PR add a fast path for testing if a cfg is enabled and is expected.

This cache reduce the number of lookup from 2/3 to just 1 (in the good path).

Currently:

• when there are no expecteds cfgs, we do 2 lookup (one for finding if the cfg is enabled and the second for trying to get the expected values)
• when there are some expecteds cfgs, we do 3 lookup in the good case (same as above + one to see if the value is in the expected values) and 2 in the "bad" case

With this PR we will only do 1 lookup if the cfg is expected (aka the good case) no matter if the cfg is actually enabled or not. See the PR changes/commits for more details.

The perf runs done below shows that there is no to a slightly improvement, which is expected as we do less work, but we also don't have any benchmark with many cfgs to be assertive.

[rustbot]

r? @oli-obk

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[matthiaskrgr]

@bors try @rust-timer queue

[rustbot]

Failed to set assignee to ghost: invalid assignee

Note: Only org members with at least the repository "read" role, users with write permissions, or people who have commented on the PR may be assigned.

[bors]

⌛ Trying commit 24d06a9 with merge 4ee97b1...

[workingjubilee]

@Urgau I believe the handling specially-recognizes r? @ghost in the PR opening.

In any case, it's somewhat useless after-the-fact, as they will remain subscribed to the thread and must manually unsubscribe.

[Urgau]

Yeah, I kinda knew about it but I was hoping I was wrong 😄, but the real issue is that rustbot didn't considered the Draft status and assigned someone anyway. It should have waited for the status to changed; but that's a topic for another time.

[bors]

☀️ Try build successful - checks-actions
Build commit: 4ee97b1 (4ee97b1068420a05fa2f91425b1a5f83f240767f)

[rust-timer]

Finished benchmarking commit (4ee97b1): comparison URL.

Overall result: ✅ improvements - no 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.

@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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.9%	[-2.9%, -2.9%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.9%	[-2.9%, -2.9%]	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
Regressions ❌ (secondary)	1.8%	[1.2%, 2.1%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.7%	[-4.9%, -2.5%]	2
All ❌✅ (primary)	-	-	0

Cycles

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

Binary size

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

Bootstrap: 649.894s -> 649.476s (-0.06%)
Artifact size: 172.55 MiB -> 172.57 MiB (0.01%)

[workingjubilee]

hot unambiguous perf results!

[Urgau]

No perf improvement or regression, which is expected since don't have any check-cfg or big cfg test.

Let's try an approach that includes all expected cfgs and cfg. It again shouldn't have any impact but it's switching from FxHashSet to FxHashMap so just to be sure may I get another perf run (cc @matthiaskrgr).

[matthiaskrgr]

@bors try @rust-timer queue

[bors]

⌛ Trying commit b5e463d with merge 478862c...

[bors]

☀️ Try build successful - checks-actions
Build commit: 478862c (478862ce99721d8d99c698714ab15e5601c67673)

[rust-timer]

Finished benchmarking commit (478862c): comparison URL.

Overall result: ✅ improvements - no 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.

@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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	1
All ❌✅ (primary)	-	-	0

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)	-	-	0
Improvements ✅ (primary)	-0.8%	[-0.8%, -0.8%]	1
Improvements ✅ (secondary)	-2.2%	[-2.2%, -2.2%]	1
All ❌✅ (primary)	-0.8%	[-0.8%, -0.8%]	1

Cycles

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

Binary size

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

Bootstrap: 649.076s -> 653.276s (0.65%)
Artifact size: 172.58 MiB -> 310.43 MiB (79.87%)

[Kobzol]

(The artifact size change is just getting the libLLVM.so size back, thanks to rust-lang/rustc-perf#1838).

[Urgau]

r? @petrochenkov

[petrochenkov]

This cache complicates the cfg logic, so I don't want to merge it until there are some benchmarks showing improvements.
Let's maybe block this on rust-lang/cargo#13571 reaching rustc-perf.
@rustbot blocked

[rustbot]

There are merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged.

You can start a rebase with the following commands:

$ # rebase
$ git rebase -i master
$ # delete any merge commits in the editor that appears
$ git push --force-with-lease

The following commits are merge commits:

• e6dcf99

[lqd]

@bors try @rust-timer queue

[bors]

⌛ Trying commit e6dcf99 with merge 81d5a42...

[bors]

☀️ Try build successful - checks-actions
Build commit: 81d5a42 (81d5a42c668f851052b6dc31326831d39f9eba5f)

[rust-timer]

Finished benchmarking commit (81d5a42): comparison URL.

Overall result: ❌ regressions - no 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.

@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
Regressions ❌ (secondary)	4.4%	[4.4%, 4.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-5.4%	[-5.4%, -5.4%]	1
All ❌✅ (primary)	-	-	0

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)	3.6%	[3.3%, 4.0%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 676.654s -> 676.922s (0.04%)
Artifact size: 315.91 MiB -> 315.91 MiB (0.00%)

[Urgau]

Nothing significant. Closing.