fix rewriting of non-alpha formats

When we use independent blending, we need to check every rendertarget
indevidually, not just once for all, otherwise we end up using the
wrong blend-mode for some render-targets.

Fixes these test-cases:
dEQP-GLES31.functional.draw_buffers_indexed.random.max_implementation_draw_buffers.0
dEQP-GLES31.functional.draw_buffers_indexed.random.max_implementation_draw_buffers.6
dEQP-GLES31.functional.draw_buffers_indexed.random.max_implementation_draw_buffers.14

[airlied: rebased onto master hopefully correct]
Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>

src/vrend_renderer.c

@@ -3548,6 +3548,14 @@ static inline int conv_dst_blend(int blend_factor)
    return blend_factor;
 }
 
+static inline bool is_const_blend(int blend_factor)
+{
+   return (blend_factor == PIPE_BLENDFACTOR_CONST_COLOR ||
+           blend_factor == PIPE_BLENDFACTOR_CONST_ALPHA ||
+           blend_factor == PIPE_BLENDFACTOR_INV_CONST_COLOR ||
+           blend_factor == PIPE_BLENDFACTOR_INV_CONST_ALPHA);
+}
+
 static void vrend_hw_emit_blend(struct vrend_context *ctx, struct pipe_blend_state *state)
 {
    if (state->logicop_enable != ctx->sub->hw_blend_state.logicop_enable) {
@@ -3642,28 +3650,16 @@ static void vrend_patch_blend_state(struct vrend_context *ctx)
 {
    struct pipe_blend_state new_state = ctx->sub->blend_state;
    struct pipe_blend_state *state = &ctx->sub->blend_state;
-   bool dest_alpha_only = false, dest_has_no_alpha = false;
+   bool swizzle_blend_color = false;
    struct pipe_blend_color blend_color = ctx->sub->blend_color;
    int i;
 
    if (ctx->sub->nr_cbufs == 0)
       return;
 
-   for (i = 0; i < ctx->sub->nr_cbufs; i++) {
-      if (!ctx->sub->surf[i])
-         continue;
-
-      if (vrend_format_is_emulated_alpha(ctx->sub->surf[i]->format)) {
-         dest_alpha_only = true;
-      }
-
-      if (!util_format_has_alpha(ctx->sub->surf[i]->format)) {
-         dest_has_no_alpha = true;
-      }
-   }
-
-   if (dest_alpha_only) {
    for (i = 0; i < (state->independent_blend_enable ? PIPE_MAX_COLOR_BUFS : 1); i++) {
+      if (i < ctx->sub->nr_cbufs && ctx->sub->surf[i]) {
+         if (vrend_format_is_emulated_alpha(ctx->sub->surf[i]->format)) {
             if (state->rt[i].blend_enable) {
                new_state.rt[i].rgb_src_factor = conv_a8_blend(state->rt[i].alpha_src_factor);
                new_state.rt[i].rgb_dst_factor = conv_a8_blend(state->rt[i].alpha_dst_factor);
@@ -3673,13 +3669,11 @@ static void vrend_patch_blend_state(struct vrend_context *ctx)
             new_state.rt[i].colormask = 0;
             if (state->rt[i].colormask & PIPE_MASK_A)
                new_state.rt[i].colormask |= PIPE_MASK_R;
+            if (is_const_blend(new_state.rt[i].rgb_src_factor) ||
+                is_const_blend(new_state.rt[i].rgb_dst_factor)) {
+               swizzle_blend_color = true;
             }
-      blend_color.color[0] = blend_color.color[3];
+         } else if (!util_format_has_alpha(ctx->sub->surf[i]->format)) {
-      blend_color.color[1] = 0.0f;
-      blend_color.color[2] = 0.0f;
-      blend_color.color[3] = 0.0f;
-   } else if (dest_has_no_alpha) {
-      for (i = 0; i < (state->independent_blend_enable ? PIPE_MAX_COLOR_BUFS : 1); i++) {
             if (!(is_dst_blend(state->rt[i].rgb_src_factor) ||
                   is_dst_blend(state->rt[i].rgb_dst_factor) ||
                   is_dst_blend(state->rt[i].alpha_src_factor) ||
@@ -3691,8 +3685,17 @@ static void vrend_patch_blend_state(struct vrend_context *ctx)
             new_state.rt[i].alpha_dst_factor = conv_dst_blend(state->rt[i].alpha_dst_factor);
          }
       }
+   }
 
    vrend_hw_emit_blend(ctx, &new_state);
+
+   if (swizzle_blend_color) {
+      blend_color.color[0] = blend_color.color[3];
+      blend_color.color[1] = 0.0f;
+      blend_color.color[2] = 0.0f;
+      blend_color.color[3] = 0.0f;
+   }
+
    glBlendColor(blend_color.color[0],
                 blend_color.color[1],
                 blend_color.color[2],