In LexicalResolver, don't construct graph unless necessary.

[nnethercote]

A small but easy perf win.

r? @jackh726

[nnethercote]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 8e6c9e0 with merge 6afef3bc826bb1dbbb61b0357520d5233e630105...

[lqd]

r=me with the expected perf improvement

[bors]

☀️ Try build successful - checks-actions
Build commit: 6afef3bc826bb1dbbb61b0357520d5233e630105 (6afef3bc826bb1dbbb61b0357520d5233e630105)

[rust-timer]

Finished benchmarking commit (6afef3bc826bb1dbbb61b0357520d5233e630105): 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)	0.6%	[0.6%, 0.6%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.4%	[-0.7%, -0.2%]	11
All ❌✅ (primary)	0.6%	[0.6%, 0.6%]	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)	4.0%	[4.0%, 4.0%]	1
Regressions ❌ (secondary)	3.8%	[3.8%, 3.8%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-2.4%, -2.4%]	1
All ❌✅ (primary)	4.0%	[4.0%, 4.0%]	1

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.3%	[-2.4%, -2.2%]	2
All ❌✅ (primary)	-	-	0

[lqd]

The cargo incr regression looks unrelated (and in a scenario we don't deploy), about encoding/decoding, while the wins are defo in the lexical resolver.

 79,826,049  ???:rustc_middle::ty::codec::encode_with_shorthand::<rustc_query_impl::on_disk_cache::CacheEncoder, rustc_middle::ty::Ty, <rustc_query_impl::on_disk_cache::CacheEncoder as rustc_type_ir::codec::TyEncoder>::type_shorthands>
-45,260,416  ???:<std::collections::hash::map::HashMap<rustc_hir::hir_id::ItemLocalId, rustc_middle::ty::Ty, core::hash::BuildHasherDefault<rustc_hash::FxHasher>> as rustc_serialize::serialize::Encodable<rustc_query_impl::on_disk_cache::CacheEncoder>>::encode
 24,158,243  ???:llvm::FPPassManager::runOnModule(llvm::Module&)
 21,446,668  <all-jemalloc-files>:<all-jemalloc-functions>
-19,908,056  ???:<rustc_middle::ty::subst::GenericArg as rustc_serialize::serialize::Decodable<rustc_query_impl::on_disk_cache::CacheDecoder>>::decode
-14,140,935  ???:<std::collections::hash::map::HashMap<rustc_hir::hir_id::ItemLocalId, alloc::vec::Vec<rustc_middle::ty::adjustment::Adjustment>, core::hash::BuildHasherDefault<rustc_hash::FxHasher>> as rustc_serialize::serialize::Encodable<rustc_query_impl::on_disk_cache::CacheEncoder>>::encode
 13,388,280  ???:<rustc_query_impl::on_disk_cache::CacheDecoder as rustc_type_ir::codec::TyDecoder>::cached_ty_for_shorthand::<<rustc_middle::ty::Ty as rustc_serialize::serialize::Decodable<rustc_query_impl::on_disk_cache::CacheDecoder>>::decode::{closure#0}>
 13,322,106  ???:<[rustc_middle::ty::subst::GenericArg] as rustc_serialize::serialize::Encodable<rustc_query_impl::on_disk_cache::CacheEncoder>>::encode
 13,185,582  ???:<&rustc_middle::ty::list::List<rustc_middle::ty::subst::GenericArg> as rustc_serialize::serialize::Decodable<rustc_query_impl::on_disk_cache::CacheDecoder>>::decode
...

[nnethercote]

Weird results. It's easier to focus on just the full check measurements:

• #110520.
• #110527

The best results are better in #110527, e.g. unused-warnings improves from -0.58% to -0.72, and libc-0.2.124 improves from -0.11% to -0.22%. Which aligns with what I saw locally, and makes logical sense: this PR is simply doing less work. But the results for #110520 are more uniformly green.

[nnethercote]

I will try another perf run, to see what happens.

@bors try @rust-timer queue

[bors]

⌛ Trying commit 8e6c9e0 with merge 2085cd2cd2f0c42c70e3d0fe60fcbb25036397e9...

[bors]

☀️ Try build successful - checks-actions
Build commit: 2085cd2cd2f0c42c70e3d0fe60fcbb25036397e9 (2085cd2cd2f0c42c70e3d0fe60fcbb25036397e9)

[rust-timer]

Finished benchmarking commit (2085cd2cd2f0c42c70e3d0fe60fcbb25036397e9): 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)	-0.5%	[-0.7%, -0.4%]	5
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

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

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)	0.7%	[0.7%, 0.7%]	1
Regressions ❌ (secondary)	2.8%	[2.6%, 3.1%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.7%	[0.7%, 0.7%]	1

[nnethercote]

Latest results are better, showing that the supposed sub-significance-threshold reds were just noise. I think it's reasonable to merge this now.

@bors r=lqd

[bors]

📌 Commit 8e6c9e0 has been approved by lqd

It is now in the queue for this repository.

[bors]

⌛ Testing commit 8e6c9e0 with merge 23a76a8...

[bors]

☀️ Test successful - checks-actions
Approved by: lqd
Pushing 23a76a8 to master...

[rust-timer]

Finished benchmarking commit (23a76a8): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -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)	-0.3%	[-0.4%, -0.2%]	4
Improvements ✅ (secondary)	-0.4%	[-0.8%, -0.2%]	11
All ❌✅ (primary)	-0.3%	[-0.4%, -0.2%]	4

Max RSS (memory usage)

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

Cycles

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