Compute data layout of types #13490

HKalbasi · 2022-10-26T21:38:40Z

Things that aren't working:

Closures
Generators (so no support for Future I think)
Opaque types
Type alias and associated types which may need normalization

Things that show wrong result:

~~Enums with explicit discriminant~~
SIMD types
~~NonZero* and similar standard library items which control layout with special attributes~~

At the user level, I didn't put much work, since I wasn't confident about what is the best way to present this information. Currently it shows size and align for ADTs, and size, align, offset for struct fields, in the hover, similar to clangd. I used it some days and I feel I liked it, but we may consider it too noisy and move it to an assist or command.

jonas-schievink

I'm somewhat worried about maintainability here. This copies 2000 lines from rustc instead of factoring the functionality out into a reusable crate, which is going to be hard to keep in sync.

crates/hir-ty/src/layout/tests.rs

jonas-schievink · 2022-10-27T13:48:14Z

crates/hir-ty/src/layout/target.rs

+        f32_align: AbiAndPrefAlign::new(Align::from_bytes(4).unwrap()),
+        f64_align: AbiAndPrefAlign::new(Align::from_bytes(8).unwrap()),
+        pointer_size,
+        pointer_align: AbiAndPrefAlign::new(Align::from_bytes(8).unwrap()),


This value is not correct on all targets (and others potentially too)

This is now fixed. About others, instruction_address_space is wrong for Harvard architectures but it doesn't affect layout computation, and vector_align is wrong but is for SIMD types which are not supported. I believe the rest is correct for at least x86, arm, riscv and powerpc.

HKalbasi · 2022-10-28T15:08:49Z

rust-lang/rust#103693 can reduce ~800 lines of copied codes. But since rustc_ap_* crates aren't updated for a long time, are we actually able to use rustc crates if they are buildable on stable? How we can upgrade rustc_lexer if needed?

lnicola · 2022-11-12T07:51:59Z

But since rustc_ap_* crates aren't updated for a long time, are we actually able to use rustc crates if they are buildable on stable?

I'm not familiar with the process of publishing those, but what do you mean? I remember rustc-ap-rustc_lexer being published pretty quickly (though I think we're behind on updating that).

HKalbasi · 2022-11-12T09:12:47Z

The last published version is a year or so old: https://crates.io/crates/rustc-ap-rustc_lexer/versions. Before that it was published every week.

crates/hir-def/Cargo.toml

HKalbasi · 2022-11-12T20:50:26Z

I updated the PR to use the new rustc_abi crate. There is no longer pure copy pasted code here, and the whole layout code is around 400 lines of code. I expect the rustc side to not change significantly, so I think this can be reviewed and especially if a change is needed on rustc's side, I can do it before the merge.

It can even be merged before the rustc PR, since I published my fork to the crates.io and it works at the current state. I will come with a follow up PR when my changes in rustc merged and rustc auto publish story becomes clear.

@rustbot review

Make rustc_target usable outside of rustc I'm working on showing type size in rust-analyzer (rust-lang/rust-analyzer#13490) and I currently copied rustc code inside rust-analyzer, which works, but is bad. With this change, I would become able to use `rustc_target` and `rustc_index` directly in r-a, reducing the amount of copy needed. This PR contains some feature flag to put nightly features behind them to make crates buildable on the stable compiler + makes layout related types generic over index type + removes interning of nested layouts.

HKalbasi · 2022-11-25T09:08:03Z

rust-lang/rust#103693 just merged, and I updated my auto published crates to use upstream rustc.

bors · 2022-11-29T08:40:57Z

☔ The latest upstream changes (presumably #13686) made this pull request unmergeable. Please resolve the merge conflicts.

Make rustc_target usable outside of rustc I'm working on showing type size in rust-analyzer (rust-lang/rust-analyzer#13490) and I currently copied rustc code inside rust-analyzer, which works, but is bad. With this change, I would become able to use `rustc_target` and `rustc_index` directly in r-a, reducing the amount of copy needed. This PR contains some feature flag to put nightly features behind them to make crates buildable on the stable compiler + makes layout related types generic over index type + removes interning of nested layouts.

jonas-schievink

This looks pretty good!

crates/hir-ty/src/layout/tests.rs

lib/la-arena/src/lib.rs

jonas-schievink · 2022-12-02T15:29:39Z

crates/hir-ty/src/layout/tests.rs

+            check_size_and_align(
+                stringify!($($t)*),
+                ::std::mem::size_of::<Goal>() as u64,
+                ::std::mem::align_of::<Goal>() as u64,


Neat trick! This should even work when cross-compiling r-a.

jonas-schievink · 2022-12-02T15:31:23Z

crates/hir-ty/src/layout/target.rs

+        i16_align: AbiAndPrefAlign::new(Align::from_bytes(2).unwrap()),
+        i32_align: AbiAndPrefAlign::new(Align::from_bytes(4).unwrap()),
+        i64_align: AbiAndPrefAlign::new(Align::from_bytes(8).unwrap()),
+        i128_align: AbiAndPrefAlign::new(Align::from_bytes(8).unwrap()),


I don't think the alignment of i64 and i128 are always 8 Bytes on all platforms. If there's no way to query the correct alignment from the cfg_options, can you add a FIXME comment?

There is a way: rustc +nightly -Z unstable-options --print target-spec-json. But it needs nightly. Is it possible to use it?

The rustc_cfg code already tries to use nightly-only features, and falls back to stable-compatible behavior if those are unavailable or don't work, so this should be doable. However, I think just setting the align to 8 should be fine for now, we can follow up with a fix that asks rustc later.

At least aarch64 and riscv64 use a 16 byte alignment for u/i128.

Added a fixme comment

jonas-schievink · 2022-12-07T14:17:01Z

@bors r+

jonas-schievink · 2022-12-07T15:21:55Z

@bors r+

bors · 2022-12-07T15:21:58Z

📌 Commit 948a8f0 has been approved by jonas-schievink

It is now in the queue for this repository.

bors · 2022-12-07T15:22:11Z

⌛ Testing commit 948a8f0 with merge 6e8a54d...

bors · 2022-12-07T15:38:09Z

☀️ Test successful - checks-actions
Approved by: jonas-schievink
Pushing 6e8a54d to master...

Show type info on hover of enum variant fields Small addition to #13490

lnicola · 2022-12-12T13:54:05Z

Show type alias layout This PR expands on #13490 to allow displaying layout data on hover for type aliases.

HKalbasi force-pushed the layout branch from 0e36d93 to ab94c4b Compare October 26, 2022 22:09

jonas-schievink reviewed Oct 27, 2022

View reviewed changes

HKalbasi mentioned this pull request Oct 28, 2022

Make rustc_target usable outside of rustc rust-lang/rust#103693

Merged

mati865 mentioned this pull request Oct 29, 2022

Feature request: Show the size/alignment of a type intellij-rust/intellij-rust#9329

Open

Veykril added the S-blocked Status: marked as blocked ❌ on something else such as an RFC or other implementation work. label Nov 3, 2022

HKalbasi force-pushed the layout branch 2 times, most recently from 8041c03 to f47fb10 Compare November 11, 2022 21:36

HKalbasi force-pushed the layout branch 2 times, most recently from ae65739 to 6601b73 Compare November 12, 2022 20:24

bjorn3 reviewed Nov 12, 2022

View reviewed changes

crates/hir-def/Cargo.toml Outdated Show resolved Hide resolved

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-blocked Status: marked as blocked ❌ on something else such as an RFC or other implementation work. labels Nov 12, 2022

HKalbasi force-pushed the layout branch from 6601b73 to 3dd033e Compare November 15, 2022 16:04

HKalbasi requested a review from jonas-schievink November 15, 2022 16:46

HKalbasi force-pushed the layout branch from 3dd033e to 8086647 Compare November 25, 2022 09:05

HKalbasi force-pushed the layout branch 2 times, most recently from 0bc0aed to c627fc4 Compare November 30, 2022 15:02

jonas-schievink reviewed Dec 2, 2022

View reviewed changes

HKalbasi added 2 commits December 4, 2022 00:29

Compute data layout of types

86b5b60

support nonzero* niche optimizations

f2c9502

HKalbasi force-pushed the layout branch from c627fc4 to 83cc14e Compare December 3, 2022 20:59

use rustc crates instead of copy paste

05906da

HKalbasi force-pushed the layout branch from 83cc14e to 05906da Compare December 6, 2022 22:29

Add a fixme comment in current_target_data_layout

948a8f0

bors merged commit 6e8a54d into rust-lang:master Dec 7, 2022

Veykril mentioned this pull request Dec 9, 2022

Show type info on hover of enum variant fields #13745

Merged

bors added a commit that referenced this pull request Dec 9, 2022

Auto merge of #13745 - Veykril:ty-hint-variant-field, r=Veykril

a0296c2

Show type info on hover of enum variant fields Small addition to #13490

lnicola mentioned this pull request Dec 12, 2022

Assist/Codelens to show size of type #4091

Closed

NobodyXu mentioned this pull request Dec 13, 2022

How to print type size? simrat39/rust-tools.nvim#292

Closed

lumenian mentioned this pull request May 6, 2023

fix: Show type alias layout #14748

Merged

bors added a commit that referenced this pull request May 6, 2023

Auto merge of #14748 - lumenian:type-alias-layout, r=HKalbasi

a10fd83

Show type alias layout This PR expands on #13490 to allow displaying layout data on hover for type aliases.

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Compute data layout of types #13490

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