[Mesa-dev] [PATCH] glsl: use var with initializer on global var validation

[Juan A. Suarez Romero]

Currently, when cross validating global variables, all global variables
seen in the shaders that are part of a program are saved in a table.

When checking a variable this already exist in the table, we check both
are initialized to the same value. If the already saved variable does
not have an initializer, we copy it from the new variable.

Unfortunately this is wrong, as we are modifying something it is
constant. Also, if this modified variable is used in
another program, it will keep the initializer, when it should have none.

Instead of copying the initializer, this commit replaces the old
variable with the new one. So if we see again the same variable with an
initializer, we can compare if both are the same or not.
---
 src/compiler/glsl/glsl_symbol_table.cpp | 10 ++++++++++
 src/compiler/glsl/glsl_symbol_table.h   |  5 +++++
 src/compiler/glsl/linker.cpp            | 27 +++++----------------------
 3 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/src/compiler/glsl/glsl_symbol_table.cpp b/src/compiler/glsl/glsl_symbol_table.cpp
index 6c682ac..6d7baad 100644
--- a/src/compiler/glsl/glsl_symbol_table.cpp
+++ b/src/compiler/glsl/glsl_symbol_table.cpp
@@ -278,3 +278,13 @@ glsl_symbol_table::disable_variable(const char *name)
       entry->v = NULL;
    }
 }
+
+void
+glsl_symbol_table::replace_variable(const char *name,
+                                    ir_variable *v)
+{
+   symbol_table_entry *entry = get_entry(name);
+   if (entry != NULL) {
+      entry->v = v;
+   }
+}
diff --git a/src/compiler/glsl/glsl_symbol_table.h b/src/compiler/glsl/glsl_symbol_table.h
index 5d654e5..2f94d4c 100644
--- a/src/compiler/glsl/glsl_symbol_table.h
+++ b/src/compiler/glsl/glsl_symbol_table.h
@@ -100,6 +100,11 @@ struct glsl_symbol_table {
     */
    void disable_variable(const char *name);
 
+   /**
+    * Replaces the variable in the entry by the new variable.
+    */
+   void replace_variable(const char *name, ir_variable *v);
+
 private:
    symbol_table_entry *get_entry(const char *name);
 
diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
index 9c72478..4522734 100644
--- a/src/compiler/glsl/linker.cpp
+++ b/src/compiler/glsl/linker.cpp
@@ -1093,21 +1093,11 @@ cross_validate_globals(struct gl_shader_program *prog,
 		     return;
 		  }
 	       } else {
-		  /* If the first-seen instance of a particular uniform did not
-		   * have an initializer but a later instance does, copy the
-		   * initializer to the version stored in the symbol table.
-		   */
-		  /* FINISHME: This is wrong.  The constant_value field should
-		   * FINISHME: not be modified!  Imagine a case where a shader
-		   * FINISHME: without an initializer is linked in two different
-		   * FINISHME: programs with shaders that have differing
-		   * FINISHME: initializers.  Linking with the first will
-		   * FINISHME: modify the shader, and linking with the second
-		   * FINISHME: will fail.
-		   */
-		  existing->constant_initializer =
-		     var->constant_initializer->clone(ralloc_parent(existing),
-						      NULL);
+		  /* If the first-seen instance of a particular uniform did
+		   * not have an initializer but a later instance does,
+		   * replace the former with the later.
+                   */
+                  variables.replace_variable(existing->name, var);
 	       }
 	    }
 
@@ -1121,13 +1111,6 @@ cross_validate_globals(struct gl_shader_program *prog,
 			       var->name);
 		  return;
 	       }
-
-	       /* Some instance had an initializer, so keep track of that.  In
-		* this location, all sorts of initializers (constant or
-		* otherwise) will propagate the existence to the variable
-		* stored in the symbol table.
-		*/
-	       existing->data.has_initializer = true;
 	    }
 
 	    if (existing->data.invariant != var->data.invariant) {
-- 
2.5.5