Fix races conditions with SyntaxContext decoding

[Zoxc]

This changes SyntaxContext decoding to work with concurrent decoding. The remapped_ctxts field now only stores SyntaxContext which have completed decoding, while the new decoding and local_in_progress keeps track of SyntaxContexts which are in process of being decoding and on which threads.

This fixes 2 issues with the current implementation. It can return an SyntaxContext which contains dummy data if another thread starts decoding before the first one has completely finished. Multiple threads could also allocate multiple SyntaxContexts for the same raw_id.

[rustbot]

r? @cjgillot

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

[Zoxc]

This could use a perf run.

[cjgillot]

@bors try @rust-timer queue

[bors]

⌛ Trying commit e41240e with merge 7251ff878f99800ce3b521cacac760ceb8c60931...

[bors]

☀️ Try build successful - checks-actions
Build commit: 7251ff878f99800ce3b521cacac760ceb8c60931 (7251ff878f99800ce3b521cacac760ceb8c60931)

[rust-timer]

Finished benchmarking commit (7251ff878f99800ce3b521cacac760ceb8c60931): 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)	0.2%	[0.2%, 0.2%]	3
Regressions ❌ (secondary)	0.3%	[0.2%, 0.4%]	7
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[0.2%, 0.2%]	3

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)	2.5%	[2.5%, 2.5%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
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: 634.844s -> 635.738s (0.14%)
Artifact size: 346.96 MiB -> 347.13 MiB (0.05%)

[cjgillot]

Perf: unfiltered results show small improvements and small regressions balancing out.
@bors r+

[bors]

📌 Commit 246a6a6 has been approved by cjgillot

It is now in the queue for this repository.

[bors]

⌛ Testing commit 246a6a6 with merge b60e31b...

[bors]

☀️ Test successful - checks-actions
Approved by: cjgillot
Pushing b60e31b to master...

[rust-timer]

Finished benchmarking commit (b60e31b): 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)	0.3%	[0.2%, 0.3%]	4
Regressions ❌ (secondary)	0.3%	[0.3%, 0.4%]	7
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[0.2%, 0.3%]	4

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)	-2.7%	[-2.7%, -2.7%]	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)	2.1%	[2.1%, 2.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 630.156s -> 630.278s (0.02%)
Artifact size: 315.55 MiB -> 315.65 MiB (0.03%)