Exclude relnotes-tracking-issue from needs-triage #4
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Noratrieb
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Sep 24, 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, 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, rust-lang#7 vadd.f64 d0, d0, d1 add r1, r0, rust-lang#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
Noratrieb
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Oct 17, 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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