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| author | Jubilee <workingjubilee@gmail.com> | 2024-09-15 23:51:25 -0700 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2024-09-15 23:51:25 -0700 |
| commit | 68758c05604f0ae4dfbe25f61e70f1a3db083c29 (patch) | |
| tree | a5a0b0691b27a39e3bcf701bb4d8bdfc14817607 | |
| parent | 0151cbe6e8ca1027f5482c98a1b93d70fbd9a50b (diff) | |
| parent | ab8c2025279077fcfb0992c455bb8c173b2d9e53 (diff) | |
| download | rust-68758c05604f0ae4dfbe25f61e70f1a3db083c29.tar.gz rust-68758c05604f0ae4dfbe25f61e70f1a3db083c29.zip | |
Rollup merge of #130325 - workingjubilee:plus-minus-zero-redux, r=RalfJung,jieyouxu
Use -0.0 in `intrinsics::simd::reduce_add_unordered` -0.0 is the actual neutral additive float, not +0.0, and this matters to codegen. try-job: aarch64-gnu
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/intrinsic.rs | 4 | ||||
| -rw-r--r-- | tests/assembly/simd/reduce-fadd-unordered.rs | 29 |
2 files changed, 31 insertions, 2 deletions
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs index 9705dd506b9..15c519dfcb4 100644 --- a/compiler/rustc_codegen_llvm/src/intrinsic.rs +++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs @@ -2066,14 +2066,14 @@ fn generic_simd_intrinsic<'ll, 'tcx>( }; } - arith_red!(simd_reduce_add_ordered: vector_reduce_add, vector_reduce_fadd, true, add, 0.0); + arith_red!(simd_reduce_add_ordered: vector_reduce_add, vector_reduce_fadd, true, add, -0.0); arith_red!(simd_reduce_mul_ordered: vector_reduce_mul, vector_reduce_fmul, true, mul, 1.0); arith_red!( simd_reduce_add_unordered: vector_reduce_add, vector_reduce_fadd_reassoc, false, add, - 0.0 + -0.0 ); arith_red!( simd_reduce_mul_unordered: vector_reduce_mul, diff --git a/tests/assembly/simd/reduce-fadd-unordered.rs b/tests/assembly/simd/reduce-fadd-unordered.rs new file mode 100644 index 00000000000..fa9ce6bd35e --- /dev/null +++ b/tests/assembly/simd/reduce-fadd-unordered.rs @@ -0,0 +1,29 @@ +//@ revisions: x86_64 aarch64 +//@ assembly-output: emit-asm +//@ compile-flags: --crate-type=lib -O +//@[aarch64] only-aarch64 +//@[x86_64] only-x86_64 +//@[x86_64] compile-flags: -Ctarget-feature=+sse3 +#![feature(portable_simd)] +#![feature(core_intrinsics)] +use std::intrinsics::simd as intrinsics; +use std::simd::*; +// Regression test for https://github.com/rust-lang/rust/issues/130028 +// This intrinsic produces much worse code if you use +0.0 instead of -0.0 because +// +0.0 isn't as easy to algebraically reassociate, even using LLVM's reassoc attribute! +// It would emit about an extra fadd, depending on the architecture. + +// CHECK-LABEL: reduce_fadd_negative_zero +pub unsafe fn reduce_fadd_negative_zero(v: f32x4) -> f32 { + // x86_64: addps + // x86_64-NEXT: movshdup + // x86_64-NEXT: addss + // x86_64-NOT: xorps + + // aarch64: faddp + // aarch64-NEXT: faddp + + // CHECK-NOT: {{f?}}add{{p?s*}} + // CHECK: ret + intrinsics::simd_reduce_add_unordered(v) +} |