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@renovate renovate bot commented Dec 10, 2024

This PR contains the following updates:

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dorny/paths-filter action digest 1441771 -> de90cc6

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@renovate renovate bot changed the title Update dorny/paths-filter digest to de90cc6 Update dorny/paths-filter digest to de90cc6 - abandoned Dec 10, 2024
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renovate bot commented Dec 10, 2024

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@Kobzol Kobzol closed this Dec 10, 2024
Kobzol pushed a commit that referenced this pull request Sep 15, 2025
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, #12
    stmib   sp, {r2, r3}
    vmov    d0, r0, r1
    add     r0, sp, #4
    vldr    d1, [sp, #4]
    add     r0, r0, #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, #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, #12
    stmib   sp, {r2, r3}
    vmov    d16, r0, r1
    vldr    d17, [sp, #4]
    vadd.f64        d16, d16, d17
    vldr    d17, [sp, #12]
    vadd.f64        d16, d16, d17
    vmov    r0, r1, d16
    add     sp, sp, #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
Kobzol pushed a commit that referenced this pull request Oct 13, 2025
…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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2 participants