[Mesa-dev] [PATCH] radv: lower ffma in nir.

[Dave Airlie]

From: Dave Airlie <airlied at redhat.com>

So it appears the Vulkan SPIR-V fma opcode can be equivalent to a
mad operation, and the fma hw opcode on AMD hw is issued like a double
opcode so is slower. Also the radeonsi stack does this.

This appears to improve performance on a number of games from Feral,
and thanks to Feral for noticing the problem.

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

diff --git a/src/amd/vulkan/radv_shader.c b/src/amd/vulkan/radv_shader.c
index ca0ad2d..a37345b 100644
--- a/src/amd/vulkan/radv_shader.c
+++ b/src/amd/vulkan/radv_shader.c
@@ -64,6 +64,7 @@ static const struct nir_shader_compiler_options nir_options = {
 	.lower_unpack_unorm_4x8 = true,
 	.lower_extract_byte = true,
 	.lower_extract_word = true,
+	.lower_ffma = true,
 	.max_unroll_iterations = 32
 };
 
-- 
2.9.5