swrast: Fix fixed-function fragment processing

On i965, _mesa_ir_link_shader is never called. As a consequence, the
current fragment program (ctx->FragmentProgram->_Current) exists but is
invalid because it has no instructions. Yet swrast continued to attempt to
use the empty program.

To avoid using the empty program, this patch 1) defines a new function,
_swrast_use_fragment_program, which checks if the current fragment program
exists and differs from the fixed function fragment program, and, when
appropriate, 2) replaces checks of the form
    if (ctx->FragmentProgram->_Current == NULL)
with
    if (_swrast_use_fragment_program(ctx))

Fixes the following oglconform regressions on i965/gen6:
    api-fogcoord(basic.allCases.log)
    api-mtexcoord(basic.allCases.log)
    api-seccolor(basic.allCases.log)
    api-texcoord(basic.allCases.log)
    blend-separate(basic.allCases)
    colorsum(basic.allCases.log)

The tests were ran with the GLXFBConfig:
    visual  x   bf lv rg d st  colorbuffer  sr ax dp st accumbuffer ms  cav
  id dep cl sp  sz l  ci b ro  r  g  b  a F gb bf th cl  r  g  b  a ns b eat
----------------------------------------------------------------------------
0x021 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0 24 8  0  0  0  0  0 0 None

(Note: I originally believed that the hunk in
_swrast_update_fragment_program was unnecessary. But it is required to fix
blend-separate.)

Note: This is a candidate for the 8.0 branch.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=43327
Reveiwed-by: Eric Anholt <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>
Signed-off-by: Chad Versace <[email protected]>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/mesa/swrast/s_triangle.c b/src/mesa/swrast/s_triangle.c
index 124aa5f8edd..ddb4792f7e9 100644
--- a/src/mesa/swrast/s_triangle.c
+++ b/src/mesa/swrast/s_triangle.c
@@ -1038,7 +1038,7 @@ _swrast_choose_triangle( struct gl_context *ctx )
        * needs to be interpolated.
        */
       if (ctx->Texture._EnabledCoordUnits ||
-          ctx->FragmentProgram._Current ||
+	  _swrast_use_fragment_program(ctx) ||
           ctx->ATIFragmentShader._Enabled ||
           _mesa_need_secondary_color(ctx) ||
           swrast->_FogEnabled) {
@@ -1060,7 +1060,7 @@ _swrast_choose_triangle( struct gl_context *ctx )
 
          /* First see if we can use an optimized 2-D texture function */
          if (ctx->Texture._EnabledCoordUnits == 0x1
-             && !ctx->FragmentProgram._Current
+             && !_swrast_use_fragment_program(ctx)
              && !ctx->ATIFragmentShader._Enabled
              && ctx->Texture._EnabledUnits == 0x1
              && ctx->Texture.Unit[0]._ReallyEnabled == TEXTURE_2D_BIT