[Mesa-dev] [PATCH] radeonsi: Fix w component of TGSI_SEMANTIC_POSITION fragment shader inputs.

[Michel Dänzer]

From: Michel Dänzer <michel.daenzer at amd.com>

It's the reciprocal of the register value.

Fixes piglit fragcoord_w and glsl-fs-fragcoord-zw-perspective.

NOTE: This is a candidate for the 9.1 branch.

Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
---
 src/gallium/drivers/radeonsi/radeonsi_shader.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/gallium/drivers/radeonsi/radeonsi_shader.c b/src/gallium/drivers/radeonsi/radeonsi_shader.c
index 704f859..7922928 100644
--- a/src/gallium/drivers/radeonsi/radeonsi_shader.c
+++ b/src/gallium/drivers/radeonsi/radeonsi_shader.c
@@ -263,6 +263,14 @@ static void declare_input_fs(
 				build_intrinsic(base->gallivm->builder,
 					"llvm.SI.fs.read.pos", input_type,
 					args, 1, LLVMReadNoneAttribute);
+
+			if (chan == 3)
+				/* RCP for fragcoord.w */
+				si_shader_ctx->radeon_bld.inputs[soa_index] =
+					LLVMBuildFDiv(gallivm->builder,
+						      lp_build_const_float(gallivm, 1.0f),
+						      si_shader_ctx->radeon_bld.inputs[soa_index],
+						      "");
 		}
 		return;
 	}
-- 
1.8.1.3