Shrink rustc_parse_format::Piece

[WaffleLapkin]

This makes both variants closer together in size (previously they were different by 208 bytes -- 16 vs 224). This may make things worse, but it's worth a try.

r? @nnethercote

[Kobzol]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 78060cb with merge 246e5ade5454a7cc83867bc0bcb8603bda642504...

[bors]

☀️ Try build successful - checks-actions
Build commit: 246e5ade5454a7cc83867bc0bcb8603bda642504 (246e5ade5454a7cc83867bc0bcb8603bda642504)

[rust-timer]

Finished benchmarking commit (246e5ade5454a7cc83867bc0bcb8603bda642504): 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)	-0.4%	[-0.6%, -0.3%]	4
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)	1.1%	[1.1%, 1.1%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-2.6%, -2.2%]	3
All ❌✅ (primary)	1.1%	[1.1%, 1.1%]	2

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)	2.2%	[1.4%, 3.0%]	3
Regressions ❌ (secondary)	3.1%	[3.1%, 3.1%]	1
Improvements ✅ (primary)	-0.6%	[-0.6%, -0.6%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[-0.6%, 3.0%]	4

[rust-timer]

Finished benchmarking commit (246e5ade5454a7cc83867bc0bcb8603bda642504): 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)	-0.4%	[-0.6%, -0.3%]	4
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)	1.1%	[1.1%, 1.1%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-2.6%, -2.2%]	3
All ❌✅ (primary)	1.1%	[1.1%, 1.1%]	2

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)	2.2%	[1.4%, 3.0%]	3
Regressions ❌ (secondary)	3.1%	[3.1%, 3.1%]	1
Improvements ✅ (primary)	-0.6%	[-0.6%, -0.6%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[-0.6%, 3.0%]	4

[nnethercote]

Some sub-1% instruction count wins on deep-vector, plus an intriguing but possibly too-good-to-be-true -0.4% reduction in bootstrap time.

@WaffleLapkin Do you still want to proceed? If so, adding a static_assert_size! would be a good idea. Otherwise, the code changes are fine.

[WaffleLapkin]

@nnethercote Added the assert 👍🏻
@rustbot label -A-bootstrap

[nnethercote]

@bors r+

[bors]

📌 Commit e4b4d25315abaf0022a2ee53953f63daaae67382 has been approved by nnethercote

It is now in the queue for this repository.

[nnethercote]

Wait, there's a size assertion failure:

error[E0308]: mismatched types
   --> /checkout/compiler/rustc_index/src/lib.rs:29:32
    |
27  | macro_rules! static_assert_size {
    | ------------------------------- in this expansion of `rustc_data_structures::static_assert_size!`
28  |     ($ty:ty, $size:expr) => {
29  |         const _: [(); $size] = [(); ::std::mem::size_of::<$ty>()];
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected an array with a fixed size of 24 elements, found one with 16 elements
    |
   ::: compiler/rustc_parse_format/src/lib.rs:913:1
    |
913 | rustc_data_structures::static_assert_size!(Piece<'_>, 24);
    | --------------------------------------------------------- in this macro invocation

@bors r-

[nnethercote]

Yeah, 16 seems the right size: 8 bytes for the tag, and 8 bytes for the single pointer/Box field in each variant.

[WaffleLapkin]

Right, I forgot that I test on arm xD

Yeah, 16 seems the right size: 8 bytes for the tag, and 8 bytes for the single pointer/Box field in each variant.

This is not actually right, the first field is &str, which is 16 bytes, the tag is actually 0 bytes, I assume instead of a 8 bytes tag we use &str's niche.

[nnethercote]

@bors r+

[bors]

📌 Commit c44c82d has been approved by nnethercote

It is now in the queue for this repository.

[bors]

🌲 The tree is currently closed for pull requests below priority 10. This pull request will be tested once the tree is reopened.

[bors]

⌛ Testing commit c44c82d with merge 0d5573e...

[bors]

☀️ Test successful - checks-actions
Approved by: nnethercote
Pushing 0d5573e to master...

[rust-timer]

Finished benchmarking commit (0d5573e): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

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)	1.6%	[1.6%, 1.6%]	1
Improvements ✅ (primary)	-3.0%	[-3.0%, -3.0%]	1
Improvements ✅ (secondary)	-0.8%	[-1.0%, -0.8%]	3
All ❌✅ (primary)	-3.0%	[-3.0%, -3.0%]	1

Cycles

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