proc_macro/bridge: stop using a remote object handle for proc_macro Punct and Group #98188

mystor · 2022-06-17T04:32:42Z

This is the third part of #86822, split off as requested in #86822 (review). This patch transforms the Punct and Group types into structs serialized over IPC rather than handles, making them more efficient to create and manipulate from within proc-macros.

rust-highfive · 2022-06-17T04:32:47Z

r? @petrochenkov

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mystor · 2022-06-17T04:32:52Z

r? @eddyb

bors · 2022-06-18T10:44:47Z

☔ The latest upstream changes (presumably #98186) made this pull request unmergeable. Please resolve the merge conflicts.

proc_macro/bridge: cache static spans in proc_macro's client thread-local state This is the second part of rust-lang#86822, split off as requested in rust-lang#86822 (review). This patch removes the RPC calls required for the very common operations of `Span::call_site()`, `Span::def_site()` and `Span::mixed_site()`. Some notes: This part is one of the ones I don't love as a final solution from a design standpoint, because I don't like how the spans are serialized immediately at macro invocation. I think a more elegant solution might've been to reserve special IDs for `call_site`, `def_site`, and `mixed_site` at compile time (either starting at 1 or from `u32::MAX`) and making reading a Span handle automatically map these IDs to the relevant values, rather than doing extra serialization. This would also have an advantage for potential future work to allow `proc_macro` to operate more independently from the compiler (e.g. to reduce the necessity of `proc-macro2`), as methods like `Span::call_site()` could be made to function without access to the compiler backend. That was unfortunately tricky to do at the time, as this was the first part I wrote of the patches. After the later part (rust-lang#98188, rust-lang#98189), the other uses of `InternedStore` are removed meaning that a custom serialization strategy for `Span` is easier to implement. If we want to go that path, we'll still need the majority of the work to split the bridge object and introduce the `Context` trait for free methods, and it will be easier to do after `Span` is the only user of `InternedStore` (after rust-lang#98189).

This greatly reduces round-trips to fetch relevant extra information about the token in proc macro code, and avoids RPC messages to create Punct tokens.

This greatly reduces round-trips to fetch relevant extra information about the token in proc macro code, and avoids RPC messages to create Group tokens.

eddyb · 2022-06-27T10:57:45Z

Before I forget (please don't force-push while this is ongoing):

@bors try @rust-timer queue

rust-timer · 2022-06-27T10:57:46Z

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

bors · 2022-06-27T10:57:53Z

⌛ Trying commit f28dfdf with merge 0b6ba9689c4b846a039c5ba15f8fcde0251749ed...

eddyb

LGTM, mostly nits as usual (reminder not to force push until perf run is finished, I think bors gets confused easily).

library/proc_macro/src/bridge/mod.rs

eddyb · 2022-06-27T10:51:22Z

library/proc_macro/src/lib.rs

+        const LEGAL_CHARS: &[char] = &[
+            '=', '<', '>', '!', '~', '+', '-', '*', '/', '%', '^', '&', '|', '@', '.', ',', ';',
+            ':', '#', '$', '?', '\'',
+        ];
+        if !LEGAL_CHARS.contains(&ch) {
+            panic!("unsupported character `{:?}`", ch);
+        }


Shouldn't something like this be a match? That way, LLVM can optimize it to some arithmetic and bit twiddling?

(Oops, just checked and this is what it takes: https://godbolt.org/z/vP13eKjsW - I guess that's pretty nasty)

If you are going to use an array search, can you do an ASCII check first and make it a bytestring literal? So that it at least can hit some kind of memchr specialization or w/e.

Sure, that's an easy change. The current code is literally verbatim cut-pasted from the code which used to be in proc_macro_server.rs:

rust/compiler/rustc_expand/src/proc_macro_server.rs

Lines 301 to 307 in bd2e51a

const LEGAL_CHARS: &[char] = &[

'=', '<', '>', '!', '~', '+', '-', '*', '/', '%', '^', '&', '|', '@', '.', ',', ';',

':', '#', '$', '?', '\'',

];

if !LEGAL_CHARS.contains(&ch) {

panic!("unsupported character `{:?}`", ch)

}

.

FWIW the current code appears to actually compile to a somewhat efficient jump table (https://godbolt.org/z/P9d5366YT), and sloppily switching it to use &[u8] instead does appear to make it use memchr (https://godbolt.org/z/EfvaaMbbh)

The existing codegen seems like the nicest of the options (I wouldn't be too surprised if it performs better than the memchr variant), so I'm inclined to stick with it.

compiler/rustc_expand/src/proc_macro_server.rs

library/proc_macro/src/bridge/mod.rs

compiler/rustc_expand/src/proc_macro_server.rs

eddyb · 2022-06-27T11:24:59Z

compiler/rustc_expand/src/proc_macro_server.rs

+                Interpolated(nt) => {
+                    let stream = TokenStream::from_nonterminal_ast(&nt);
+                    if crate::base::nt_pretty_printing_compatibility_hack(&nt, rustc.sess()) {
+                        trees.extend(Self::from_internal((stream, rustc)));


If this Self::from_internal didn't go through a weird method trait, I would definitely suggest passing &mut Vec here (would help with any future experiments like using SmallVec<[_; 32]> instead of Vec, as there would be no expensive moves).

FWIW I'm not sure this codepath is worth optimizing given it's only for that pretty-printing compatibility hack, meaning it only impacts enums with the name ProceduralMasqueradeDummyType.

Fair, though in the SmallVec<[_; 32]> case, I'm worried the rarely-used codepath would still cause worse cache behavior for the whole function.

compiler/rustc_expand/src/proc_macro_server.rs

bors · 2022-06-27T12:31:26Z

☀️ Try build successful - checks-actions
Build commit: 0b6ba9689c4b846a039c5ba15f8fcde0251749ed (0b6ba9689c4b846a039c5ba15f8fcde0251749ed)

rust-timer · 2022-06-27T12:31:36Z

Queued 0b6ba9689c4b846a039c5ba15f8fcde0251749ed with parent bd2e51a, future comparison URL.

rust-timer · 2022-06-27T13:36:21Z

Finished benchmarking commit (0b6ba9689c4b846a039c5ba15f8fcde0251749ed): comparison url.

Instruction count

Primary benchmarks: 🎉 relevant improvements found
Secondary benchmarks: 🎉 relevant improvements found

	mean¹	max	count²
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	-0.5%	-1.4%	17
Improvements 🎉 (secondary)	-1.5%	-5.1%	17
All 😿🎉 (primary)	-0.5%	-1.4%	17

Max RSS (memory usage)

Results

Primary benchmarks: no relevant changes found
Secondary benchmarks: 😿 relevant regression found

	mean¹	max	count²
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	2.3%	2.3%	1
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	N/A	N/A	0
All 😿🎉 (primary)	N/A	N/A	0

Cycles

Results

Primary benchmarks: no relevant changes found
Secondary benchmarks: mixed results

	mean¹	max	count²
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	3.0%	3.0%	1
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-3.3%	-3.5%	3
All 😿🎉 (primary)	N/A	N/A	0

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

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-review -S-waiting-on-perf -perf-regression

the arithmetic mean of the percent change ↩ ↩² ↩³
number of relevant changes ↩ ↩² ↩³

eddyb

r=me with at least the comment fixed (and the PR description updated)

compiler/rustc_expand/src/proc_macro_server.rs

longer names for RPC generics and reduced dependency on macros in the server.

eddyb · 2022-06-28T14:02:38Z

@bors r+

bors · 2022-06-28T14:02:41Z

📌 Commit 64a7d57 has been approved by eddyb

bors · 2022-06-28T16:10:34Z

⌛ Testing commit 64a7d57 with merge 94e9374...

bors · 2022-06-28T18:36:30Z

☀️ Test successful - checks-actions
Approved by: eddyb
Pushing 94e9374 to master...

rust-timer · 2022-06-28T20:03:27Z

Finished benchmarking commit (94e9374): comparison url.

Instruction count

Primary benchmarks: 🎉 relevant improvements found
Secondary benchmarks: 🎉 relevant improvements found

	mean¹	max	count²
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	-0.5%	-1.4%	15
Improvements 🎉 (secondary)	-1.6%	-5.0%	16
All 😿🎉 (primary)	-0.5%	-1.4%	15

Max RSS (memory usage)

Results

Primary benchmarks: no relevant changes found
Secondary benchmarks: mixed results

	mean¹	max	count²
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	1.0%	1.0%	1
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-3.2%	-3.4%	2
All 😿🎉 (primary)	N/A	N/A	0

Cycles

Results

Primary benchmarks: no relevant changes found
Secondary benchmarks: 🎉 relevant improvements found

	mean¹	max	count²
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	2.7%	2.7%	1
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-3.4%	-4.6%	6
All 😿🎉 (primary)	N/A	N/A	0

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

the arithmetic mean of the percent change ↩ ↩² ↩³
number of relevant changes ↩ ↩² ↩³

Unbreak stage1 tests via ignore-stage1 in `proc-macro/invalid-punct-ident-1.rs`. rust-lang#98188 broke `./x.py test --stage 1` (which I thought we ran in PR CI, cc `@rust-lang/infra)` i.e. the default `./x.py test` in dev checkouts, as the panic in `src/test/ui/proc-macro/invalid-punct-ident-1.rs` moved from the server (`rustc`) to the client (proc macro), and that means it's now affected by rust-lang#59998. I made the test look like `src/test/ui-fulldeps/issue-76270-panic-in-libproc-macro.rs` tho I'm a bit confused why that one is in `src/test/ui-fulldeps`, it should still work in `src/test/ui`, no? (cc `@Aaron1011)`

…idge This is done by having the crossbeam dependency inserted into the proc_macro server code from the server side, to avoid adding a dependency to proc_macro. In addition, this introduces a -Z command-line option which will switch rustc to run proc-macros using this cross-thread executor. With the changes to the bridge in rust-lang#98186, rust-lang#98187, rust-lang#98188 and rust-lang#98189, the performance of the executor should be much closer to same-thread execution. In local testing, the crossbeam executor was substantially more performant than either of the two existing CrossThread strategies, so they have been removed to keep things simple.

proc_macro: use crossbeam channels for the proc_macro cross-thread bridge This is done by having the crossbeam dependency inserted into the `proc_macro` server code from the server side, to avoid adding a dependency to `proc_macro`. In addition, this introduces a -Z command-line option which will switch rustc to run proc-macros using this cross-thread executor. With the changes to the bridge in rust-lang#98186, rust-lang#98187, rust-lang#98188 and rust-lang#98189, the performance of the executor should be much closer to same-thread execution. In local testing, the crossbeam executor was substantially more performant than either of the two existing `CrossThread` strategies, so they have been removed to keep things simple. r? `@eddyb`

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rust-highfive assigned petrochenkov Jun 17, 2022

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Jun 17, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 17, 2022

rust-highfive assigned eddyb and unassigned petrochenkov Jun 17, 2022

This was referenced Jun 17, 2022

proc_macro/bridge: stop using a remote object handle for proc_macro Ident and Literal #98189

Merged

reduce RPC overhead for common proc_macro operations #86822

Closed

mystor force-pushed the fast_group_punct branch from 21f1847 to e4e8d8c Compare June 17, 2022 04:45

mystor mentioned this pull request Jun 17, 2022

Batch proc_macro RPC for TokenStream iteration and combination operations #98186

Merged

mystor mentioned this pull request Jun 18, 2022

proc_macro/bridge: cache static spans in proc_macro's client thread-local state #98187

Merged

mystor changed the title ~~Stop using a remote object handle for proc_macro Punct and Group~~ proc_macro/bridge: stop using a remote object handle for proc_macro Punct and Group Jun 18, 2022

mystor force-pushed the fast_group_punct branch 2 times, most recently from 2dd6d7d to 51b2749 Compare June 26, 2022 17:07

mystor added 2 commits June 26, 2022 22:20

proc_macro: stop using a remote object handle for Punct

72bfe61

This greatly reduces round-trips to fetch relevant extra information about the token in proc macro code, and avoids RPC messages to create Punct tokens.

proc_macro: stop using a remote object handle for Group

f28dfdf

This greatly reduces round-trips to fetch relevant extra information about the token in proc macro code, and avoids RPC messages to create Group tokens.

mystor force-pushed the fast_group_punct branch from 51b2749 to f28dfdf Compare June 27, 2022 02:25

mystor marked this pull request as ready for review June 27, 2022 02:27

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jun 27, 2022

eddyb requested changes Jun 27, 2022

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jun 27, 2022

mystor force-pushed the fast_group_punct branch from bbb4f23 to 819c0de Compare June 28, 2022 00:15

eddyb requested changes Jun 28, 2022

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review changes

64a7d57

longer names for RPC generics and reduced dependency on macros in the server.

mystor force-pushed the fast_group_punct branch from 819c0de to 64a7d57 Compare June 28, 2022 13:54

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 28, 2022

bors added the merged-by-bors This PR was explicitly merged by bors. label Jun 28, 2022

bors merged commit 94e9374 into rust-lang:master Jun 28, 2022

rustbot added this to the 1.64.0 milestone Jun 28, 2022

eddyb mentioned this pull request Jun 29, 2022

Unbreak stage1 tests via ignore-stage1 in proc-macro/invalid-punct-ident-1.rs. #98660

Merged

mystor mentioned this pull request Jul 10, 2022

proc_macro: use crossbeam channels for the proc_macro cross-thread bridge #99123

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flodiebold mentioned this pull request Jul 13, 2022

Proc macro server crashed rust-lang/rust-analyzer#12600

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proc_macro/bridge: stop using a remote object handle for proc_macro Punct and Group #98188

proc_macro/bridge: stop using a remote object handle for proc_macro Punct and Group #98188

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rust-timer commented Jun 28, 2022

	const LEGAL_CHARS: &[char] = &[
	'=', '<', '>', '!', '~', '+', '-', '*', '/', '%', '^', '&', '\|', '@', '.', ',', ';',
	':', '#', '$', '?', '\'',
	];
	if !LEGAL_CHARS.contains(&ch) {
	panic!("unsupported character `{:?}`", ch)
	}

proc_macro/bridge: stop using a remote object handle for proc_macro Punct and Group #98188

proc_macro/bridge: stop using a remote object handle for proc_macro Punct and Group #98188

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