remove interior mutability of type-flags #42015

nikomatsakis · 2017-05-15T19:03:08Z

We were previously using the flags on Ty<'tcx> instances to do some ad-hoc caching schemes around things like is_sized(), is_freeze(), and moves_by_default(). This PR replaces those schemes with a proper query; the query key is based on the pair of a (ParameterEnvironment<'tcx>, Ty<'tcx>) pair. This is also intended to be a preliminary template for what trait-selection and projection will eventually look like.

I did some performance measurements. In the past, I observed a noticeable speedup (6%) for building rustc, but since I've rebased, the numbers appear to be more of a wash:

Crate	Before	After	Percentage
syntax	167s	166s	0.6% faster
rustc	376s	382s	1.5% slower

Some advantages of this new scheme:

is_sized etc are proper queries
we get caching across generic fns, so long as trait environment is identical
dependency tracking is correct

rust-highfive · 2017-05-15T19:03:12Z

r? @eddyb

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nikomatsakis · 2017-05-15T19:03:51Z

cc @arielb1

eddyb · 2017-05-15T19:18:17Z

src/librustc/ty/mod.rs

Only two flags removed?

Mark-Simulacrum

Just some minor nits, no need to bother if you don't want to.

Mark-Simulacrum · 2017-05-15T19:53:14Z

src/librustc/infer/mod.rs

We could just use ty::ParameterEnvironment here and avoid adding the import.

Speaking of which, renaming it to ParamEnv might be a good idea?

I always go back and forth on the importing question. I tend to prefer the import, so as to avoid having to write modules everywhere, and comply more closely with the Rust style guidelines (which suggest importing types, but not fns) -- but it does mean more merge conflicts around use declarations, which is annoying.

Mark-Simulacrum · 2017-05-15T20:09:46Z

src/librustc/ty/mod.rs

I think this is now small enough to be a u16 instead of a u32 bitflags!

It was always wasteful, heh. And I think due to padding it ends up using a lot anyway.

Mark-Simulacrum · 2017-05-15T20:13:09Z

src/librustc_trans/context.rs

Minor, but we could avoid the additional import with ty::ParamEnv. I think this occurs elsewhere, too.

eddyb · 2017-05-15T20:22:04Z

src/librustc/ty/mod.rs

eddyb · 2017-05-15T20:24:46Z

src/librustc/ty/util.rs

I see you killed some of the shortcutting?

I figured it'd fall out from the caching anyway.

eddyb

LGTM, modulo nits.

nikomatsakis · 2017-05-15T22:08:05Z

ok, I made some style changes (s/ParameterEnvironment/ParamEnv/, removed imports) -- I haven't finished building this locally yet though :)

Mark-Simulacrum · 2017-05-15T23:29:34Z

src/librustc/traits/README.md

This looks wrong, but is minor. Should ideally be "to the ParamEnv".

Mark-Simulacrum · 2017-05-15T23:32:47Z

src/librustc/ty/util.rs

This is again somewhat painful to me since we use both ty::ParamEnv and ParamEnv in this file. Don't bother fixing if you don't want to though.

bors · 2017-05-18T00:37:02Z

☔ The latest upstream changes (presumably #41911) made this pull request unmergeable. Please resolve the merge conflicts.

carols10cents · 2017-05-22T16:47:57Z

@nikomatsakis looks like this is back in your court now, friendly ping!

Use the trait-environment+type as the key. Note that these are only invoked on types that live for the entire compilation (no inference artifacts). We no longer need the various special-case bits and caches that were in place before.

Ideally, we'd have the `Ty` inserted directly in the dep-node, but since we can't do that yet, we extract the characteristic def-id of the type in question.

nikomatsakis · 2017-05-22T21:23:46Z

@bors r=eddyb

bors · 2017-05-22T21:23:47Z

📌 Commit 83641a9 has been approved by eddyb

bors · 2017-05-23T07:14:48Z

⌛ Testing commit 83641a9 with merge 9fa25a7...

remove interior mutability of type-flags We were previously using the flags on `Ty<'tcx>` instances to do some ad-hoc caching schemes around things like `is_sized()`, `is_freeze()`, and `moves_by_default()`. This PR replaces those schemes with a proper query; the query key is based on the pair of a `(ParameterEnvironment<'tcx>, Ty<'tcx>)` pair. This is also intended to be a preliminary template for what trait-selection and projection will eventually look like. I did some performance measurements. In the past, I observed a noticeable speedup (6%) for building rustc, but since I've rebased, the numbers appear to be more of a wash: | Crate | Before | After | Percentage | | --- | --- | --- | -- | | syntax | 167s | 166s | 0.6% faster | | rustc | 376s | 382s | 1.5% slower | Some advantages of this new scheme: - `is_sized` etc are proper queries - we get caching across generic fns, so long as trait environment is identical - dependency tracking is correct

bors · 2017-05-23T09:55:35Z

☀️ Test successful - status-appveyor, status-travis
Approved by: eddyb
Pushing 9fa25a7 to master...

rust-highfive assigned eddyb May 15, 2017

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Only two flags removed?

nikomatsakis force-pushed the chalk-trait-env-2 branch from 617ed25 to aa511ce Compare May 15, 2017 20:03

Mark-Simulacrum reviewed May 15, 2017

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😻

eddyb reviewed May 15, 2017

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eddyb approved these changes May 15, 2017

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nikomatsakis force-pushed the chalk-trait-env-2 branch from 4f431a4 to 3977ee7 Compare May 16, 2017 10:07

arielb1 added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 16, 2017

carols10cents 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 May 22, 2017

nikomatsakis added 12 commits May 22, 2017 14:55

make parameter-environment a query

194d4bc

refactor common logic into ParameterEnvironment::and()

5a5c265

move needs_drop into a query

b46c1a9

remove the cell from type flags completely

4464dcc

kill SIZEDNESS_CACHED

aa5232b

kill FREEZENESS_CACHED

25ea618

kill NEEDS_DROP_CACHED

ca65a8a

rename ParameterEnvironment to ParamEnv

226358e

use ParamEnv from ty rather than importing

697146b

rename parameter_environment to param_env

45dd063

two more style nits

9317d37

nikomatsakis force-pushed the chalk-trait-env-2 branch from e3435fb to 15abc19 Compare May 22, 2017 20:02

nikomatsakis added 2 commits May 22, 2017 17:11

fix DepNode

0436710

Ideally, we'd have the `Ty` inserted directly in the dep-node, but since we can't do that yet, we extract the characteristic def-id of the type in question.

fix atomic_lock_free test case

83641a9

nikomatsakis force-pushed the chalk-trait-env-2 branch from d9dab46 to 83641a9 Compare May 22, 2017 21:23

bors merged commit 83641a9 into rust-lang:master May 23, 2017

dwrensha mentioned this pull request May 24, 2017

update for upstream changes with ty::ParamEnv rust-lang/miri#170

Merged

est31 mentioned this pull request May 25, 2017

Regression from stable: "Unexpected tail in unsized_info_ty" #42210

Closed

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remove interior mutability of type-flags #42015

remove interior mutability of type-flags #42015

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nikomatsakis commented May 15, 2017 •

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