Mesa (10.1): glsl: Compile error if fs uses gl_FragCoord before first redeclaration

[Carl Worth]

Module: Mesa
Branch: 10.1
Commit: 33f85d51b7aa4ff322b5727c9a94ee7409640dd9
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=33f85d51b7aa4ff322b5727c9a94ee7409640dd9

Author: Anuj Phogat <anuj.phogat at gmail.com>
Date:   Thu Feb 20 18:32:25 2014 -0800

glsl: Compile error if fs uses gl_FragCoord before first redeclaration

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.phogat at gmail.com>
Cc: <mesa-stable at lists.freedesktop.org>
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
(cherry picked from commit a751adf07117ec4b3659fe60d0a833ebfcd4f840)

---

 src/glsl/ast_to_hir.cpp |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index c04b6ae..c5996fa 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -2387,6 +2387,23 @@ apply_type_qualifier_to_variable(const struct ast_type_qualifier *qual,
 
    if (var->name != NULL && 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) {
+         _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.
        */