dont clone old syntax context

[bvanjoi]

I guess this regression was caused by too many clones, so this is an attempt to use the old value rather than cloning it. Perhaps a better approach would be to ensure that only the substantial fields mentioned in this comment are cacheable.

Anyway, let's run a perf test to see if this can solve the problem.

r? @pnkfelix or @petrochenkov

[compiler-errors]

@bors try @rust-timer queue

[bors]

⌛ Trying commit efd2619 with merge 89b1569...

[bors]

☀️ Try build successful - checks-actions
Build commit: 89b1569 (89b15693dc0b42d4bbdfe7f1b9718511c36f8194)

[rust-timer]

Finished benchmarking commit (89b1569): comparison URL.

Overall result: ❌✅ regressions and improvements - 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
Regressions ❌ (secondary)	0.4%	[0.4%, 0.4%]	2
Improvements ✅ (primary)	-0.5%	[-0.6%, -0.3%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.5%	[-0.6%, -0.3%]	3

Max RSS (memory usage)

Results (primary -0.0%, secondary -0.1%)

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)	1.1%	[0.4%, 2.3%]	14
Regressions ❌ (secondary)	0.8%	[0.5%, 2.5%]	22
Improvements ✅ (primary)	-0.7%	[-1.7%, -0.4%]	25
Improvements ✅ (secondary)	-0.8%	[-3.1%, -0.4%]	33
All ❌✅ (primary)	-0.0%	[-1.7%, 2.3%]	39

Cycles

Results (primary -0.2%, 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)	1.7%	[0.4%, 6.4%]	9
Regressions ❌ (secondary)	1.3%	[0.4%, 6.5%]	48
Improvements ✅ (primary)	-0.9%	[-3.8%, -0.4%]	25
Improvements ✅ (secondary)	-1.0%	[-5.3%, -0.4%]	41
All ❌✅ (primary)	-0.2%	[-3.8%, 6.4%]	34

Binary size

Results (primary -0.5%)

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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.5%	[-0.5%, -0.5%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.5%	[-0.5%, -0.5%]	2

Bootstrap: 788.226s -> 788.556s (0.04%)
Artifact size: 338.74 MiB -> 338.72 MiB (-0.01%)

[bvanjoi]

It shows a slight performance improvement, and I will give it a try by only encoding/decoding the essential fields to see if it makes a difference.

@rustbot blocked