gallium: Make TGSI_SEMANTIC_FOG register four-component wide.

D3D9 Shader Model 2 restricted the fog register to one component,
http://msdn.microsoft.com/en-us/library/windows/desktop/bb172945.aspx ,
but that restriction no longer exists in Shader Model 3, and several
WHCK tests enforce that.

So this change:
- lifts the single-component restriction TGSI_SEMANTIC_FOG
  from Gallium interface
- updates the Mesa state tracker to enforce output fog has (f, 0, 0, 1)
- draw module was updated to leave TGSI_SEMANTIC_FOG output registers
  alone

Several gallium drivers that are going out of their way to clear
TGSI_SEMANTIC_FOG components could be simplified in the future.

Thanks to Si Chen and Michal Krol for identifying the problem.

Testing done: piglit fogcoord-*.vpfp tests

Reviewed-by: Roland Scheidegger <sroland@vmware.com>

1 files changed, 1 insertions, 6 deletions

diff --git a/src/gallium/auxiliary/draw/draw_vs_exec.c b/src/gallium/auxiliary/draw/draw_vs_exec.c
index 610039498a..83cc5fda5a 100644
--- a/src/gallium/auxiliary/draw/draw_vs_exec.c
+++ b/src/gallium/auxiliary/draw/draw_vs_exec.c
@@ -167,12 +167,7 @@ vs_exec_run_linear( struct draw_vertex_shader *shader,
                output[slot][2] = CLAMP(machine->Outputs[slot].xyzw[2].f[j], 0.0f, 1.0f);
                output[slot][3] = CLAMP(machine->Outputs[slot].xyzw[3].f[j], 0.0f, 1.0f);
             }
-            else if (name == TGSI_SEMANTIC_FOG) {
-               output[slot][0] = machine->Outputs[slot].xyzw[0].f[j];
-               output[slot][1] = 0;
-               output[slot][2] = 0;
-               output[slot][3] = 1;
-	    } else
+            else
             {
                output[slot][0] = machine->Outputs[slot].xyzw[0].f[j];
                output[slot][1] = machine->Outputs[slot].xyzw[1].f[j];