vrend: Ignore prev shader stages in shader key when procesing unbound shaders

Gallium sends the shaders in the order FS-[GS]-[TES]-[TCS]-VS. If an old
shader program is still bound when a new shader is send, then it would use the
old bounds shader of the previous stage to evaluate the shader key and code
creation might create an invalid shader. Hence, if the shader to be translated
is not yet bound ignore the previous stage when evaluating the shader key
(Gurchtan)

Fixes #114

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>

src/vrend_renderer.c

@@ -3036,9 +3036,11 @@ static inline bool can_emulate_logicop(enum pipe_logicop op)
 
 
 static inline void vrend_fill_shader_key(struct vrend_context *ctx,
-                                         unsigned type,
+                                         struct vrend_shader_selector *sel,
                                          struct vrend_shader_key *key)
 {
+   unsigned type = sel->type;
+
    if (vrend_state.use_core_profile == true) {
       int i;
       bool add_alpha_test = true;
@@ -3090,6 +3092,11 @@ static inline void vrend_fill_shader_key(struct vrend_context *ctx,
 
    int prev_type = -1;
 
+   /* Gallium sends and binds the shaders in the reverse order, so if an
+    * old shader is still bound we should ignore the "previous" (as in
+    * execution order) shader when the key is evaluated, unless the currently
+    * bound shader selector is actually refers to the current shader. */
+   if (ctx->sub->shaders[type] == sel) {
       switch (type) {
       case PIPE_SHADER_GEOMETRY:
          if (key->tcs_present || key->tes_present)
@@ -3117,6 +3124,8 @@ static inline void vrend_fill_shader_key(struct vrend_context *ctx,
       default:
          break;
       }
+   }
+
    if (prev_type != -1 && ctx->sub->shaders[prev_type]) {
       key->prev_stage_pervertex_out = ctx->sub->shaders[prev_type]->sinfo.has_pervertex_out;
       key->prev_stage_num_clip_out = ctx->sub->shaders[prev_type]->sinfo.num_clip_out;
@@ -3227,7 +3236,7 @@ static int vrend_shader_select(struct vrend_context *ctx,
    int r;
 
    memset(&key, 0, sizeof(key));
-   vrend_fill_shader_key(ctx, sel->type, &key);
+   vrend_fill_shader_key(ctx, sel, &key);
 
    if (sel->current && !memcmp(&sel->current->key, &key, sizeof(key)))
       return 0;
@@ -4151,7 +4160,7 @@ void vrend_inject_tcs(struct vrend_context *ctx, int vertices_per_patch)
                                                                  false, PIPE_SHADER_TESS_CTRL);
    struct vrend_shader *shader;
    shader = CALLOC_STRUCT(vrend_shader);
-   vrend_fill_shader_key(ctx, sel->type, &shader->key);
+   vrend_fill_shader_key(ctx, sel, &shader->key);
 
    shader->sel = sel;
    list_inithead(&shader->programs);