On 02/24/2014 05:34 PM, Anuj Phogat wrote:
Section 4.3.8.1, page 39 of GLSL 1.50 spec says:
   "Within any shader, the first redeclarations of gl_FragCoord
    must appear before any use of gl_FragCoord."

GLSL compiler should generate an error in following case:

vec4 p = gl_FragCoord;
layout(origin_upper_left) in vec4 gl_FragCoord;

void main()
{
}

Signed-off-by: Anuj Phogat <anuj.pho...@gmail.com>
Cc: <mesa-sta...@lists.freedesktop.org>
---
  src/glsl/ast_to_hir.cpp | 16 ++++++++++++++++
  1 file changed, 16 insertions(+)

diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index 9fe3095..f5dacfd 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -2490,6 +2490,22 @@ apply_type_qualifier_to_variable(const struct 
ast_type_qualifier *qual,
     }

     if (strcmp(var->name, "gl_FragCoord") == 0) {
+      /* Section 4.3.8.1, page 39 of GLSL 1.50 spec says:
+       *
+       *    "Within any shader, the first redeclarations of gl_FragCoord
+       *     must appear before any use of gl_FragCoord."
+       *
+       * Generate a compiler error if above condition is not met by the
+       * fragment shader.
+       */
+      ir_variable *earlier = state->symbols->get_variable("gl_FragCoord");
+      if (earlier != NULL &&
+          earlier->data.used &&
+          !state->fs_redeclares_gl_fragcoord) {

I don't think '!state->fs_redeclares_gl_fragcoord' should be there. What about a shader like:

    layout(origin_upper_left) in vec4 gl_FragCoord;
    vec4 p = gl_FragCoord;
    layout(origin_upper_left) in vec4 gl_FragCoord;

    void main()
    {
    }

+         _mesa_glsl_error(loc, state,
+                          "gl_FragCoord used before its first redeclaration "
+                          "in fragment shader");
+      }

        /* Make sure all gl_FragCoord redeclarations specify the same layout
         * qualifiers.


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