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ac/llvm: workaround legacy fma intrinsic crash on gfx12

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This is a llvm bug:
  https://github.com/llvm/llvm-project/issues/170437

Cc: mesa-stable
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/14359
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38884>
This commit is contained in:
Qiang Yu 2025-12-10 16:57:17 +08:00 • committed by Marge Bot
parent cb9d9b8a6e
commit 3f37740762
1 changed files with 12 additions and 2 deletions
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14
src/amd/llvm/ac_nir_to_llvm.c
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@ -857,8 +857,18 @@ static bool visit_alu(struct ac_nir_context *ctx, const nir_alu_instr *instr)
src[0] = ac_to_float(&ctx->ac, src[0]);
src[1] = ac_to_float(&ctx->ac, src[1]);
src[2] = ac_to_float(&ctx->ac, src[2]);
result = ac_build_intrinsic(&ctx->ac, "llvm.amdgcn.fma.legacy", ctx->ac.f32,
src, 3, 0);
#if LLVM_VERSION_MAJOR <= 21
/* Workaround for LLVM bug that crashes when using legacy fma on GFX12. */
if (ctx->ac.gfx_level == GFX12) {
LLVMValueRef mulz = ac_build_intrinsic(&ctx->ac, "llvm.amdgcn.fmul.legacy",
ctx->ac.f32, src, 2, 0);
result = LLVMBuildFAdd(ctx->ac.builder, mulz, src[2], "");
} else
#endif
{
result = ac_build_intrinsic(&ctx->ac, "llvm.amdgcn.fma.legacy", ctx->ac.f32,
src, 3, 0);
}
break;
case nir_op_ldexp:
src[0] = ac_to_float(&ctx->ac, src[0]);