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ac/llvm: never create ffmaz for broken llvm

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The workaround wasn't proper fused ffma.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41649>
This commit is contained in:
Georg Lehmann 2026-05-18 14:47:29 +02:00 • committed by Marge Bot
parent 015b1d9e6d
commit 3ea594f42b
2 changed files with 14 additions and 12 deletions
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12
src/amd/common/nir/ac_nir.c
View file

@ -10,6 +10,10 @@
#include "nir_builder.h"
#include "nir_intrinsics.h"
#if AMD_LLVM_AVAILABLE
#include <llvm/Config/llvm-config.h>
#endif
/* Set NIR options shared by ACO, LLVM, RADV, and radeonsi. */
void ac_nir_set_options(const struct ac_compiler_info *info, bool use_llvm,
nir_shader_compiler_options *options)
@ -144,6 +148,14 @@ void ac_nir_set_options(const struct ac_compiler_info *info, bool use_llvm,
options->max_workgroup_count[1] = UINT16_MAX;
options->max_workgroup_count[2] = UINT16_MAX;
options->max_samples = 8;
/* Workaround for LLVM bug that crashes when using legacy fma on GFX12. */
#if AMD_LLVM_AVAILABLE
if (info->gfx_level == GFX12 && use_llvm && LLVM_VERSION_MAJOR <= 21)
options->has_ffmaz_no_denorms = false;
#else
assert(!use_llvm);
#endif
}
/* Sleep for the given number of clock cycles. */

14
src/amd/llvm/ac_nir_to_llvm.c
View file

@ -767,18 +767,8 @@ 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]);
#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);
}
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]);