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1: split rustc_attr/builtins.rs to work on individual attributes with fewer conflicts #4

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@jdonszelmann jdonszelmann commented Dec 7, 2024

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@jdonszelmann jdonszelmann force-pushed the split-attributes branch 2 times, most recently from befae45 to 955ec6a Compare December 13, 2024 13:09
@jdonszelmann jdonszelmann changed the base branch from move-attribute-types to hir-attributes December 13, 2024 13:09
@jdonszelmann jdonszelmann changed the title Split attributes 1: split rustc_attr/builtins.rs to work on individual attributes with fewer conflicts Dec 13, 2024
This was referenced Dec 14, 2024
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@jdonszelmann jdonszelmann changed the base branch from hir-attributes to master December 16, 2024 11:22
jdonszelmann pushed a commit that referenced this pull request Sep 12, 2025
@Zalathar
Rollup merge of rust-lang#144549 - folkertdev:va-arg-arm, r=saethlin
48d6841 
match clang's `va_arg` assembly on arm targets

tracking issue: rust-lang#44930

For this example

```rust
#![feature(c_variadic)]

#[unsafe(no_mangle)]
unsafe extern "C" fn variadic(a: f64, mut args: ...) -> f64 {
    let b = args.arg::<f64>();
    let c = args.arg::<f64>();

    a + b + c
}
```

We currently generate (via llvm):

```asm
variadic:
    sub     sp, sp, rust-lang#12
    stmib   sp, {r2, r3}
    vmov    d0, r0, r1
    add     r0, sp, #4
    vldr    d1, [sp, #4]
    add     r0, r0, rust-lang#15
    bic     r0, r0, #7
    vadd.f64        d0, d0, d1
    add     r1, r0, #8
    str     r1, [sp]
    vldr    d1, [r0]
    vadd.f64        d0, d0, d1
    vmov    r0, r1, d0
    add     sp, sp, rust-lang#12
    bx      lr
```

LLVM is not doing a good job. In fact, it's well-known that LLVM's implementation of `va_arg` is kind of bad, and we implement it ourselves (based on clang) for many targets already. For arm,  our own `emit_ptr_va_arg` saves 3 instructions.

Next, it turns out it's important for LLVM to explicitly start and end the lifetime of the `va_list`. In rust-lang#146059 I already end the lifetime, but when looking at this again, I noticed that it is important to also start it, see https://godbolt.org/z/EGqvKTTsK: failing to explicitly start the lifetime uses an extra register.

So, the combination of `emit_ptr_va_arg` with starting/ending the lifetime makes rustc emit exactly the instructions that clang generates::

```asm
variadic:
    sub     sp, sp, rust-lang#12
    stmib   sp, {r2, r3}
    vmov    d16, r0, r1
    vldr    d17, [sp, #4]
    vadd.f64        d16, d16, d17
    vldr    d17, [sp, rust-lang#12]
    vadd.f64        d16, d16, d17
    vmov    r0, r1, d16
    add     sp, sp, rust-lang#12
    bx      lr
```

The arguments to `emit_ptr_va_arg` are based on [the clang implementation](https://github.com/llvm/llvm-project/blob/03dc2a41f3d9a500e47b513de5c5008c06860d65/clang/lib/CodeGen/Targets/ARM.cpp#L798-L844).

r? ``@workingjubilee`` (I can re-roll if your queue is too full, but you do seem like the right person here)

try-job: armhf-gnu
jdonszelmann pushed a commit that referenced this pull request Oct 14, 2025
@matthiaskrgr
Rollup merge of rust-lang#145897 - Oneirical:uncountable-integer-11, …
f58eab7 
…r=jieyouxu

Rehome 30 `tests/ui/issues/` tests to other subdirectories under `tests/ui/` [#4 of Batch #2]

Part of rust-lang#133895

Methodology:

1. Refer to the previously written `tests/ui/SUMMARY.md`
2. Find an appropriate category for the test, using the original issue thread and the test contents.
3. Add the issue URL at the bottom (not at the top, as that would mess up stderr line numbers)
4. Rename the tests to make their purpose clearer

Inspired by the methodology that `@Kivooeo` was using.

r? `@jieyouxu`
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@jdonszelmann