Compute default query providers at compile-time #87040

Aaron1011 · 2021-07-10T21:24:51Z

All of the provide functions are made const, allowing
us to compute the default local and extern query providers
entirely at compile-time.

In addition to moving runtime work to compile-time, this will
allow our internal documentation to show all query implementations,
once #87038 is implemented.

All of the `provide` functions are made `const`, allowing us to compute the default local and extern query providers entirely at compile-time. In addition to moving runtime work to compile-time, this will allow our internal documentation to show all query implementations, once rust-lang#87038 is implemented.

rust-highfive · 2021-07-10T21:24:53Z

r? @petrochenkov

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Aaron1011 · 2021-07-10T21:25:01Z

@bors try @rust-timer queue

rust-timer · 2021-07-10T21:25:02Z

Awaiting bors try build completion.

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

bors · 2021-07-10T21:25:10Z

⌛ Trying commit 366f8f3 with merge a50316edc0300b2760fd4fcb6df11c2851875464...

jyn514 · 2021-07-10T21:41:22Z

compiler/rustc_interface/src/passes.rs

@@ -737,35 +736,35 @@ pub fn prepare_outputs(
    Ok(outputs)
 }

-pub static DEFAULT_QUERY_PROVIDERS: SyncLazy<Providers> = SyncLazy::new(|| {
-    let providers = &mut Providers::default();
+pub const DEFAULT_QUERY_PROVIDERS: Providers = {


This isn't the same semantics as before, it will make a copy of the Providers struct everywhere it's used (which defeats the whole point of having this in rustc proper, originally in #73566 I just use a thread_local in rustdoc and @eddyb asked me not to for performance reasons).

Suggested change

pub const DEFAULT_QUERY_PROVIDERS: Providers = {

pub static DEFAULT_QUERY_PROVIDERS: Providers = {

We already copy DEFAULT_QUERY_PROVIDERS in both places where it's used, so making this a static will just result in an unnecessary static allocation in the final library.

It's not copied in rustdoc:

> rg DEFAULT_QUERY_PROVIDERS src/librustdoc/ src/librustdoc/core.rs 295: (rustc_interface::DEFAULT_QUERY_PROVIDERS.typeck)(tcx, def_id)

Anyway, I'm not completely opposed to changing it, but I don't think it belongs here. AIUI the point of this is to compute the providers at compiletime, which you can do without changing these to consts.

jyn514 · 2021-07-10T21:41:40Z

compiler/rustc_interface/src/passes.rs

+    providers
+};
+
+pub const DEFAULT_EXTERN_QUERY_PROVIDERS: Providers = {


Suggested change

pub const DEFAULT_EXTERN_QUERY_PROVIDERS: Providers = {

pub static DEFAULT_EXTERN_QUERY_PROVIDERS: Providers = {

petrochenkov · 2021-07-10T21:53:01Z

I know that something like this was unsuccessfully tried previously - #74283.
r? @cjgillot @eddyb

jyn514 · 2021-07-10T21:56:43Z

Oh yay, that was the PR I was looking for: #74347. Yes, changing static to const defeats the whole point of that and at that point I'm not sure what advantage the const has over a const fn.

bors · 2021-07-10T22:25:40Z

☀️ Try build successful - checks-actions
Build commit: a50316edc0300b2760fd4fcb6df11c2851875464 (a50316edc0300b2760fd4fcb6df11c2851875464)

rust-timer · 2021-07-10T22:25:41Z

Queued a50316edc0300b2760fd4fcb6df11c2851875464 with parent a31431f, future comparison URL.

rust-timer · 2021-07-11T01:39:42Z

Finished benchmarking try commit (a50316edc0300b2760fd4fcb6df11c2851875464): comparison url.

Summary: This change led to significant regressions 😿 in compiler performance.

Moderate regression in instruction counts (up to 2.3% on full builds of externs-debug)

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 led to changes in compiler perf.

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

Aaron1011 · 2021-07-11T02:00:31Z

@bors try @rust-timer queue

rust-timer · 2021-07-11T02:00:33Z

Awaiting bors try build completion.

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

bors · 2021-07-11T02:00:40Z

⌛ Trying commit aaeca08 with merge 24c4eabf24250ef1b13b23eb38ad979c56316abb...

bors · 2021-07-11T02:49:44Z

☀️ Try build successful - checks-actions
Build commit: 24c4eabf24250ef1b13b23eb38ad979c56316abb (24c4eabf24250ef1b13b23eb38ad979c56316abb)

rust-timer · 2021-07-11T02:49:45Z

Queued 24c4eabf24250ef1b13b23eb38ad979c56316abb with parent dfd7b8d, future comparison URL.

rust-timer · 2021-07-11T08:16:43Z

Finished benchmarking try commit (24c4eabf24250ef1b13b23eb38ad979c56316abb): comparison url.

Summary: This change led to significant regressions 😿 in compiler performance.

Moderate regression in instruction counts (up to 2.3% on full builds of externs-debug)

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 led to changes in compiler perf.

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

cjgillot · 2021-07-18T09:34:55Z

@Aaron1011 the changes LGTM. Do you have an idea where the perf regression could come from?

eddyb · 2021-07-18T11:15:53Z

Doesn't this PR run into the same issue described in #74283 (comment) ?

Even if you use static instead of const, the codegen for various closures will still happen in rustc_interface (i.e. the crate containing the default providers static), instead of the original crate, leading to performance regressions.

eddyb · 2021-07-18T11:16:29Z

r? @eddyb

JohnCSimon · 2021-08-09T06:25:53Z

Triage:
Returned to the author for merge conflicts.

JohnCSimon · 2021-09-13T02:01:57Z

Triage:
@Aaron1011 fyi merge conflicts

jyn514 · 2021-11-09T10:10:18Z

I'm going to close this for now since there are performance regressions and I'm unclear whether they're possible to fix: #87040 (comment)

rust-highfive assigned petrochenkov Jul 10, 2021

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 10, 2021

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 10, 2021

jyn514 suggested changes Jul 10, 2021

View reviewed changes

jyn514 added A-query-system Area: The rustc query system (https://rustc-dev-guide.rust-lang.org/query.html) T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jul 10, 2021

rust-highfive assigned cjgillot and unassigned petrochenkov Jul 10, 2021

rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Jul 11, 2021

Change const to static

aaeca08

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 11, 2021

rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 11, 2021

rust-highfive assigned eddyb and unassigned cjgillot Jul 18, 2021

JohnCSimon added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 9, 2021

camelid added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 29, 2021

JohnCSimon added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Oct 3, 2021

JohnCSimon added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Oct 19, 2021

JohnCSimon added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Nov 8, 2021

jyn514 closed this Nov 9, 2021

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Compute default query providers at compile-time #87040

Compute default query providers at compile-time #87040

Aaron1011 commented Jul 10, 2021

rust-highfive commented Jul 10, 2021

Aaron1011 commented Jul 10, 2021

rust-timer commented Jul 10, 2021

bors commented Jul 10, 2021

jyn514 Jul 10, 2021

Aaron1011 Jul 10, 2021

jyn514 Jul 10, 2021

jyn514 Jul 10, 2021

jyn514 Jul 10, 2021

petrochenkov commented Jul 10, 2021

jyn514 commented Jul 10, 2021 •

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bors commented Jul 10, 2021

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rust-timer commented Jul 11, 2021

Aaron1011 commented Jul 11, 2021

rust-timer commented Jul 11, 2021

bors commented Jul 11, 2021

bors commented Jul 11, 2021

rust-timer commented Jul 11, 2021

rust-timer commented Jul 11, 2021

cjgillot commented Jul 18, 2021

eddyb commented Jul 18, 2021

eddyb commented Jul 18, 2021

JohnCSimon commented Aug 9, 2021

JohnCSimon commented Sep 13, 2021

jyn514 commented Nov 9, 2021

	pub const DEFAULT_QUERY_PROVIDERS: Providers = {
	pub static DEFAULT_QUERY_PROVIDERS: Providers = {

	pub const DEFAULT_EXTERN_QUERY_PROVIDERS: Providers = {
	pub static DEFAULT_EXTERN_QUERY_PROVIDERS: Providers = {

Compute default query providers at compile-time #87040

Compute default query providers at compile-time #87040

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