[Mesa-dev] [PATCH 4/4] glsl: Fix gl_program::OutputsWritten computation for dual-source blending.

[Francisco Jerez]

In the fragment shader OutputsWritten is a bitset of FRAG_RESULT_*
enumerants, which represent the location of each color output written
by the shader.  The secondary and primary color outputs of a given
render target using dual-source blending have the same location, so
the 'idx' computation below will give the wrong bit as result if the
'var->data.index' term is non-zero -- E.g. if the shader writes the
primary and secondary colors of the FRAG_RESULT_COLOR output,
ir_set_program_inouts will think that the shader writes both
FRAG_RESULT_COLOR and FRAG_RESULT_SAMPLE_MASK, which is just bogus.

That would cause the brw_wm_prog_key::nr_color_regions computation
done in the i965 driver during fragment shader precompilation to be
wrong, which currently leads to unnecessary recompilation of shaders
that use dual-source blending, and triggers an assertion failure in
fs_visitor::emit_fb_writes() on my i965-fb-fetch branch.
---
 src/compiler/glsl/ir_set_program_inouts.cpp | 2 +-
 src/mesa/state_tracker/st_program.c         | 4 +---
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/compiler/glsl/ir_set_program_inouts.cpp b/src/compiler/glsl/ir_set_program_inouts.cpp
index 06d9973..4f6c886 100644
--- a/src/compiler/glsl/ir_set_program_inouts.cpp
+++ b/src/compiler/glsl/ir_set_program_inouts.cpp
@@ -96,7 +96,7 @@ mark(struct gl_program *prog, ir_variable *var, int offset, int len,
    for (int i = 0; i < len; i++) {
       assert(var->data.location != -1);
 
-      int idx = var->data.location + var->data.index + offset + i;
+      int idx = var->data.location + offset + i;
       bool is_patch_generic = var->data.patch &&
                               idx != VARYING_SLOT_TESS_LEVEL_INNER &&
                               idx != VARYING_SLOT_TESS_LEVEL_OUTER;
diff --git a/src/mesa/state_tracker/st_program.c b/src/mesa/state_tracker/st_program.c
index 429d0c9..2a4edfa 100644
--- a/src/mesa/state_tracker/st_program.c
+++ b/src/mesa/state_tracker/st_program.c
@@ -586,9 +586,7 @@ bool
 st_translate_fragment_program(struct st_context *st,
                               struct st_fragment_program *stfp)
 {
-   GLuint outputMapping[2 * FRAG_RESULT_MAX] =
-      { 0 /* XXX - Avoid temporary regression due to bogus OutputsWritten
-           *       bitset. */ };
+   GLuint outputMapping[2 * FRAG_RESULT_MAX];
    GLuint inputMapping[VARYING_SLOT_MAX];
    GLuint inputSlotToAttr[VARYING_SLOT_MAX];
    GLuint interpMode[PIPE_MAX_SHADER_INPUTS];  /* XXX size? */
-- 
2.9.0