[Mesa-dev] [PATCH 22/22] meta/blit: Use GL_EXT_shader_samples_identical in MSAA-SS resolve blit

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

Somewhat surprisingly, this didn't have any affect on performance in the
benchmarks that Martin tried for me.

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
---
 src/mesa/drivers/common/meta_blit.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/common/meta_blit.c b/src/mesa/drivers/common/meta_blit.c
index 28aabd3..c0ec51f 100644
--- a/src/mesa/drivers/common/meta_blit.c
+++ b/src/mesa/drivers/common/meta_blit.c
@@ -530,6 +530,7 @@ setup_glsl_msaa_blit_shader(struct gl_context *ctx,
          fs_source = ralloc_asprintf(mem_ctx,
                                      "#version 130\n"
                                      "#extension GL_ARB_texture_multisample: require\n"
+                                     "#extension GL_EXT_shader_samples_identical: enable\n"
                                      "#define gvec4 %svec4\n"
                                      "uniform %ssampler2DMS%s texSampler;\n"
                                      "in %s texCoords;\n"
@@ -569,7 +570,14 @@ setup_glsl_msaa_blit_shader(struct gl_context *ctx,
                                      "   i%s tc = i%s(texCoords);\n"
                                      "   int i;\n"
                                      "\n"
-                                     "   for (i = 0; i < SAMPLES; i++)\n"
+                                     "   S[0] = texelFetch(texSampler, tc, 0);\n"
+                                     "#if defined(GL_EXT_shader_samples_identical) && SAMPLES > 1\n"
+                                     "   if (textureSamplesIdenticalEXT(texSampler, tc)) {\n"
+                                     "      emit2(S[0]);\n"
+                                     "      return;\n"
+                                     "   }\n"
+                                     "#endif\n"
+                                     "   for (i = 1; i < SAMPLES; i++)\n"
                                      "      S[i] = texelFetch(texSampler, tc, i);\n"
                                      "\n"
                                      "   REDUCE(s16, s32);\n"
-- 
2.5.0