[Mesa-dev] [PATCH] radv: emit fmuladd instead of fma to llvm.

Dave Airlie airlied at gmail.com
Wed Oct 4 02:10:28 UTC 2017

From: Dave Airlie <airlied at redhat.com>

For Vulkan SPIR-V the spec states
fma() Inherited from OpFMul followed by OpFAdd.

Matt says the backend will do the right thing depending on the
hardware being compiled for, if you use the fmuladd intrinsic.

Using the Mad Max pts test, on high settings at 4K:
CHP: 55->60
HGDD: 46->50
LM: 55->60
No change on Stronghold.

Thanks to Feral for spending the time to track this down.

Signed-off-by: Dave Airlie <airlied at redhat.com>
 src/amd/common/ac_nir_to_llvm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index d7b6259..11ba487 100644
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -1707,7 +1707,7 @@ static void visit_alu(struct ac_nir_context *ctx, const nir_alu_instr *instr)
 	case nir_op_ffma:
-		result = emit_intrin_3f_param(&ctx->ac, "llvm.fma",
+		result = emit_intrin_3f_param(&ctx->ac, "llvm.fmuladd",
 		                              ac_to_float_type(&ctx->ac, def_type), src[0], src[1], src[2]);
 	case nir_op_ibitfield_extract:

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