fix instruction comment code
diff --git a/src/mesa/shader/prog_instruction.c b/src/mesa/shader/prog_instruction.c
index 1e8e081..d6b5652 100644
--- a/src/mesa/shader/prog_instruction.c
+++ b/src/mesa/shader/prog_instruction.c
@@ -108,7 +108,13 @@
 _mesa_copy_instructions(struct prog_instruction *dest,
                         const struct prog_instruction *src, GLuint n)
 {
-   return _mesa_memcpy(dest, src, n * sizeof(struct prog_instruction));
+   GLuint i;
+   _mesa_memcpy(dest, src, n * sizeof(struct prog_instruction));
+   for (i = 0; i < n; i++) {
+      if (src[i].Comment)
+         dest[i].Comment = _mesa_strdup(src[i].Comment);
+   }
+   return dest;
 }