[Mesa-dev] [PATCH 1/5] glsl: last duplicated layout-qualifier-name in a layout-qualifier overrides the former

[Andres Gomez]

In a declaration, when a layout qualifier appears and holds duplicated
layout-qualifier-name, only the last occurrence should be taken into
account.

>From page 59 (page 65 of the PDF) of the GLSL 4.40 spec:

  " More than one layout qualifier may appear in a single
    declaration. Additionally, the same layout-qualifier-name can
    occur multiple times within a layout qualifier or across multiple
    layout qualifiers in the same declaration. When the same
    layout-qualifier-name occurs multiple times, in a single
    declaration, the last occurrence overrides the former
    occurrence(s)."

Consider this example:

  " #version 150
    #extension GL_ARB_shading_language_420pack: enable
    #extension GL_ARB_enhanced_layouts: enable

    layout(max_vertices=2, max_vertices=3) out;
    layout(max_vertices=3) out;"

Although different values for the "max_vertices" layout-qualifier-name
should end in a compilation failure, since only the last occurrence is
taken into account, this small piece of code from a shader is valid.

Hence, when merging qualifiers in an ast_type_qualifier, we now ignore
new appearances of a same layout-qualifier-name if the
"is_single_layout_merge" parameter is on, since the GLSL parser works
in this case from right to left.

Signed-off-by: Andres Gomez <agomez at igalia.com>
---
 src/compiler/glsl/ast_type.cpp | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/compiler/glsl/ast_type.cpp b/src/compiler/glsl/ast_type.cpp
index b586f94..504b533 100644
--- a/src/compiler/glsl/ast_type.cpp
+++ b/src/compiler/glsl/ast_type.cpp
@@ -196,7 +196,7 @@ ast_type_qualifier::merge_qualifier(YYLTYPE *loc,
    }
 
    if (q.flags.q.max_vertices) {
-      if (this->max_vertices) {
+      if (this->max_vertices && !is_single_layout_merge) {
          this->max_vertices->merge_qualifier(q.max_vertices);
       } else {
          this->max_vertices = q.max_vertices;
@@ -213,7 +213,7 @@ ast_type_qualifier::merge_qualifier(YYLTYPE *loc,
    }
 
    if (q.flags.q.invocations) {
-      if (this->invocations) {
+      if (this->invocations && !is_single_layout_merge) {
          this->invocations->merge_qualifier(q.invocations);
       } else {
          this->invocations = q.invocations;
@@ -262,7 +262,8 @@ ast_type_qualifier::merge_qualifier(YYLTYPE *loc,
          unsigned buff_idx;
          if (process_qualifier_constant(state, loc, "xfb_buffer",
                                         this->xfb_buffer, &buff_idx)) {
-            if (state->out_qualifier->out_xfb_stride[buff_idx]) {
+            if (state->out_qualifier->out_xfb_stride[buff_idx]
+                && !is_single_layout_merge) {
                state->out_qualifier->out_xfb_stride[buff_idx]->merge_qualifier(
                   new(state) ast_layout_expression(*loc, this->xfb_stride));
             } else {
@@ -274,7 +275,7 @@ ast_type_qualifier::merge_qualifier(YYLTYPE *loc,
    }
 
    if (q.flags.q.vertices) {
-      if (this->vertices) {
+      if (this->vertices && !is_single_layout_merge) {
          this->vertices->merge_qualifier(q.vertices);
       } else {
          this->vertices = q.vertices;
@@ -312,7 +313,7 @@ ast_type_qualifier::merge_qualifier(YYLTYPE *loc,
 
    for (int i = 0; i < 3; i++) {
       if (q.flags.q.local_size & (1 << i)) {
-         if (this->local_size[i]) {
+         if (this->local_size[i] && !is_single_layout_merge) {
             this->local_size[i]->merge_qualifier(q.local_size[i]);
          } else {
             this->local_size[i] = q.local_size[i];
-- 
2.9.3