i965/fs: Assume shadow sampler swizzling is <X, X, X, 1>.

Our previous assumption, SWIZZLE_XYZW, was completely bogus for depth
textures.  There are no Y, Z, or W components.

DEPTH_TEXTURE_MODE has three options:
- GL_LUMINANCE: <X, X, X, 1>
- GL_INTENSITY: <X, X, X, X>
- GL_ALPHA:     <0, 0, 0, X>

The default value is GL_LUMINANCE, and most applications don't seem to
alter DEPTH_TEXTURE_MODE.  Make that our precompile guess.

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

1 files changed, 8 insertions, 2 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index d896b008fd7..a8d55ffc35e 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -2179,8 +2179,14 @@ brw_fs_precompile(struct gl_context *ctx, struct gl_shader_program *prog)
    key.clamp_fragment_color = true;
 
    for (int i = 0; i < MAX_SAMPLERS; i++) {
-      /* FINISHME: depth compares might use (0,0,0,W) for example */
-      key.tex.swizzles[i] = SWIZZLE_XYZW;
+      if (fp->Base.ShadowSamplers & (1 << i)) {
+         /* Assume DEPTH_TEXTURE_MODE is the default: X, X, X, 1 */
+         key.tex.swizzles[i] =
+            MAKE_SWIZZLE4(SWIZZLE_X, SWIZZLE_X, SWIZZLE_X, SWIZZLE_ONE);
+      } else {
+         /* Color sampler: assume no swizzling. */
+         key.tex.swizzles[i] = SWIZZLE_XYZW;
+      }
    }
 
    if (fp->Base.InputsRead & FRAG_BIT_WPOS) {