softpipe: Fix alpha blending for formats without alpha channel.

Don't use the dst alpha channel from the tile cache when it does not
exist in the true format.

src/gallium/drivers/softpipe/sp_quad_blend.c

@@ -33,6 +33,7 @@
 #include "pipe/p_defines.h"
 #include "util/u_math.h"
 #include "util/u_memory.h"
+#include "util/u_format.h"
 #include "sp_context.h"
 #include "sp_quad.h"
 #include "sp_tile_cache.h"
@@ -224,7 +225,8 @@ static void
 blend_quad(struct quad_stage *qs, 
            float (*quadColor)[4],
            float (*dest)[4],
-           unsigned cbuf)
+           unsigned cbuf,
+           boolean has_dst_alpha)
 {
    static const float zero[4] = { 0, 0, 0, 0 };
    static const float one[4] = { 1, 1, 1, 1 };
@@ -259,24 +261,34 @@ blend_quad(struct quad_stage *qs,
       VEC4_MUL(source[2], quadColor[2], dest[2]); /* B */
       break;
    case PIPE_BLENDFACTOR_DST_ALPHA:
-   {
-      const float *alpha = dest[3];
-      VEC4_MUL(source[0], quadColor[0], alpha); /* R */
-      VEC4_MUL(source[1], quadColor[1], alpha); /* G */
-      VEC4_MUL(source[2], quadColor[2], alpha); /* B */
-   }
-   break;
+      if (has_dst_alpha) {
+         const float *alpha = dest[3];
+         VEC4_MUL(source[0], quadColor[0], alpha); /* R */
+         VEC4_MUL(source[1], quadColor[1], alpha); /* G */
+         VEC4_MUL(source[2], quadColor[2], alpha); /* B */
+      } 
+      else {
+         VEC4_COPY(source[0], quadColor[0]); /* R */
+         VEC4_COPY(source[1], quadColor[1]); /* G */
+         VEC4_COPY(source[2], quadColor[2]); /* B */
+      }
+      break;
    case PIPE_BLENDFACTOR_SRC_ALPHA_SATURATE:
-   {
-      const float *alpha = quadColor[3];
-      float diff[4], temp[4];
-      VEC4_SUB(diff, one, dest[3]);
-      VEC4_MIN(temp, alpha, diff);
-      VEC4_MUL(source[0], quadColor[0], temp); /* R */
-      VEC4_MUL(source[1], quadColor[1], temp); /* G */
-      VEC4_MUL(source[2], quadColor[2], temp); /* B */
-   }
-   break;
+      if (has_dst_alpha) {
+         const float *alpha = quadColor[3];
+         float diff[4], temp[4];
+         VEC4_SUB(diff, one, dest[3]);
+         VEC4_MIN(temp, alpha, diff);
+         VEC4_MUL(source[0], quadColor[0], temp); /* R */
+         VEC4_MUL(source[1], quadColor[1], temp); /* G */
+         VEC4_MUL(source[2], quadColor[2], temp); /* B */
+      }
+      else {
+         VEC4_COPY(source[0], zero); /* R */
+         VEC4_COPY(source[1], zero); /* G */
+         VEC4_COPY(source[2], zero); /* B */
+      }
+      break;
    case PIPE_BLENDFACTOR_CONST_COLOR:
    {
       float comp[4];
@@ -329,14 +341,19 @@ blend_quad(struct quad_stage *qs,
    }
    break;
    case PIPE_BLENDFACTOR_INV_DST_ALPHA:
-   {
-      float inv_alpha[4];
-      VEC4_SUB(inv_alpha, one, dest[3]);
-      VEC4_MUL(source[0], quadColor[0], inv_alpha); /* R */
-      VEC4_MUL(source[1], quadColor[1], inv_alpha); /* G */
-      VEC4_MUL(source[2], quadColor[2], inv_alpha); /* B */
-   }
-   break;
+      if (has_dst_alpha) {
+         float inv_alpha[4];
+         VEC4_SUB(inv_alpha, one, dest[3]);
+         VEC4_MUL(source[0], quadColor[0], inv_alpha); /* R */
+         VEC4_MUL(source[1], quadColor[1], inv_alpha); /* G */
+         VEC4_MUL(source[2], quadColor[2], inv_alpha); /* B */
+      }
+      else {
+         VEC4_COPY(source[0], zero); /* R */
+         VEC4_COPY(source[1], zero); /* G */
+         VEC4_COPY(source[2], zero); /* B */
+      }
+      break;
    case PIPE_BLENDFACTOR_INV_DST_COLOR:
    {
       float inv_comp[4];
@@ -399,7 +416,10 @@ blend_quad(struct quad_stage *qs,
    case PIPE_BLENDFACTOR_DST_COLOR:
       /* fall-through */
    case PIPE_BLENDFACTOR_DST_ALPHA:
-      VEC4_MUL(source[3], quadColor[3], dest[3]); /* A */
+      if (has_dst_alpha)
+         VEC4_MUL(source[3], quadColor[3], dest[3]); /* A */
+      else
+         VEC4_COPY(source[3], quadColor[3]); /* A */
       break;
    case PIPE_BLENDFACTOR_SRC_ALPHA_SATURATE:
       /* multiply alpha by 1.0 */
@@ -429,12 +449,15 @@ blend_quad(struct quad_stage *qs,
    case PIPE_BLENDFACTOR_INV_DST_COLOR:
       /* fall-through */
    case PIPE_BLENDFACTOR_INV_DST_ALPHA:
-   {
-      float inv_alpha[4];
-      VEC4_SUB(inv_alpha, one, dest[3]);
-      VEC4_MUL(source[3], quadColor[3], inv_alpha); /* A */
-   }
-   break;
+      if (has_dst_alpha) {
+         float inv_alpha[4];
+         VEC4_SUB(inv_alpha, one, dest[3]);
+         VEC4_MUL(source[3], quadColor[3], inv_alpha); /* A */
+      }
+      else {
+         VEC4_COPY(source[3], zero); /* A */
+      }
+      break;
    case PIPE_BLENDFACTOR_INV_CONST_COLOR:
       /* fall-through */
    case PIPE_BLENDFACTOR_INV_CONST_ALPHA:
@@ -468,9 +491,14 @@ blend_quad(struct quad_stage *qs,
       VEC4_MUL(dest[2], dest[2], quadColor[3]); /* B * A */
       break;
    case PIPE_BLENDFACTOR_DST_ALPHA:
-      VEC4_MUL(dest[0], dest[0], dest[3]); /* R * A */
-      VEC4_MUL(dest[1], dest[1], dest[3]); /* G * A */
-      VEC4_MUL(dest[2], dest[2], dest[3]); /* B * A */
+      if (has_dst_alpha) {
+         VEC4_MUL(dest[0], dest[0], dest[3]); /* R * A */
+         VEC4_MUL(dest[1], dest[1], dest[3]); /* G * A */
+         VEC4_MUL(dest[2], dest[2], dest[3]); /* B * A */
+      }
+      else {
+         /* dest = dest * 1   NO-OP, leave dest as-is */
+      }
       break;
    case PIPE_BLENDFACTOR_DST_COLOR:
       VEC4_MUL(dest[0], dest[0], dest[0]); /* R */
@@ -478,15 +506,20 @@ blend_quad(struct quad_stage *qs,
       VEC4_MUL(dest[2], dest[2], dest[2]); /* B */
       break;
    case PIPE_BLENDFACTOR_SRC_ALPHA_SATURATE:
-   {
-      const float *alpha = quadColor[3];
-      float diff[4], temp[4];
-      VEC4_SUB(diff, one, dest[3]);
-      VEC4_MIN(temp, alpha, diff);
-      VEC4_MUL(dest[0], quadColor[0], temp); /* R */
-      VEC4_MUL(dest[1], quadColor[1], temp); /* G */
-      VEC4_MUL(dest[2], quadColor[2], temp); /* B */
-   }
+      if (has_dst_alpha) {
+         const float *alpha = quadColor[3];
+         float diff[4], temp[4];
+         VEC4_SUB(diff, one, dest[3]);
+         VEC4_MIN(temp, alpha, diff);
+         VEC4_MUL(dest[0], quadColor[0], temp); /* R */
+         VEC4_MUL(dest[1], quadColor[1], temp); /* G */
+         VEC4_MUL(dest[2], quadColor[2], temp); /* B */
+      }
+      else {
+         VEC4_COPY(dest[0], zero); /* R */
+         VEC4_COPY(dest[1], zero); /* G */
+         VEC4_COPY(dest[2], zero); /* B */
+      }
       break;
    case PIPE_BLENDFACTOR_CONST_COLOR:
    {
@@ -539,13 +572,18 @@ blend_quad(struct quad_stage *qs,
    }
    break;
    case PIPE_BLENDFACTOR_INV_DST_ALPHA:
-   {
-      float inv_comp[4];
-      VEC4_SUB(inv_comp, one, dest[3]); /* A */
-      VEC4_MUL(dest[0], inv_comp, dest[0]); /* R */
-      VEC4_MUL(dest[1], inv_comp, dest[1]); /* G */
-      VEC4_MUL(dest[2], inv_comp, dest[2]); /* B */
-   }
+      if (has_dst_alpha) {
+         float inv_comp[4];
+         VEC4_SUB(inv_comp, one, dest[3]); /* A */
+         VEC4_MUL(dest[0], inv_comp, dest[0]); /* R */
+         VEC4_MUL(dest[1], inv_comp, dest[1]); /* G */
+         VEC4_MUL(dest[2], inv_comp, dest[2]); /* B */
+      }
+      else {
+         VEC4_COPY(dest[0], zero); /* R */
+         VEC4_COPY(dest[1], zero); /* G */
+         VEC4_COPY(dest[2], zero); /* B */
+      }
    break;
    case PIPE_BLENDFACTOR_INV_DST_COLOR:
    {
@@ -605,7 +643,12 @@ blend_quad(struct quad_stage *qs,
    case PIPE_BLENDFACTOR_DST_COLOR:
       /* fall-through */
    case PIPE_BLENDFACTOR_DST_ALPHA:
-      VEC4_MUL(dest[3], dest[3], dest[3]); /* A */
+      if (has_dst_alpha) {
+         VEC4_MUL(dest[3], dest[3], dest[3]); /* A */
+      }
+      else {
+         /* dest = dest * 1   NO-OP, leave dest as-is */
+      }
       break;
    case PIPE_BLENDFACTOR_SRC_ALPHA_SATURATE:
       /* dest = dest * 1   NO-OP, leave dest as-is */
@@ -634,12 +677,15 @@ blend_quad(struct quad_stage *qs,
    case PIPE_BLENDFACTOR_INV_DST_COLOR:
       /* fall-through */
    case PIPE_BLENDFACTOR_INV_DST_ALPHA:
-   {
-      float inv_comp[4];
-      VEC4_SUB(inv_comp, one, dest[3]); /* A */
-      VEC4_MUL(dest[3], inv_comp, dest[3]); /* A */
-   }
-   break;
+      if (has_dst_alpha) {
+         float inv_comp[4];
+         VEC4_SUB(inv_comp, one, dest[3]); /* A */
+         VEC4_MUL(dest[3], inv_comp, dest[3]); /* A */
+      }
+      else {
+         VEC4_COPY(dest[3], zero); /* A */
+      }
+      break;
    case PIPE_BLENDFACTOR_INV_CONST_COLOR:
       /* fall-through */
    case PIPE_BLENDFACTOR_INV_CONST_ALPHA:
@@ -751,6 +797,8 @@ blend_fallback(struct quad_stage *qs,
          = sp_get_cached_tile(softpipe->cbuf_cache[cbuf],
                               quads[0]->input.x0, 
                               quads[0]->input.y0);
+      boolean has_dst_alpha
+         = util_format_has_alpha(softpipe->framebuffer.cbufs[cbuf]->format);
       uint q, i, j;
 
       for (q = 0; q < nr; q++) {
@@ -774,7 +822,7 @@ blend_fallback(struct quad_stage *qs,
             logicop_quad( qs, quadColor, dest );
          }
          else if (blend->rt[blend_buf].blend_enable) {
-            blend_quad( qs, quadColor, dest, cbuf );
+            blend_quad( qs, quadColor, dest, cbuf, has_dst_alpha );
          }
 
          if (blend->rt[blend_buf].colormask != 0xf)