The error location won't be right, but fixing that would require to check
for this as we process each type of AST node that can involve a variable
read.
---
src/glsl/ast_to_hir.cpp | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 49 insertions(+)
diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index 518612d..efe1787 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -67,6 +67,41 @@ static void
remove_per_vertex_blocks(exec_list *instructions,
_mesa_glsl_parse_state *state, ir_variable_mode mode);
+/**
+ * Visitor class that finds the first instance of any write-only variable that
+ * is ever read, if any
+ */
+class read_from_write_only_variable_visitor : public ir_hierarchical_visitor
+{
+public:
+ read_from_write_only_variable_visitor() : found(NULL)
+ {
+ }
+
+ virtual ir_visitor_status visit(ir_dereference_variable *ir)
+ {
+ if (this->in_assignee)
+ return visit_continue;
+
+ ir_variable *var = ir->variable_referenced();
+ if (!var)
+ return visit_continue;
+
+ if (var->data.image_write_only) {
+ found = var;
+ return visit_stop;
+ }
+
+ return visit_continue;
+ }
+
+ ir_variable *get_variable() {
+ return found;
+ }
+
+private:
+ ir_variable *found;
+};
void
_mesa_ast_to_hir(exec_list *instructions, struct _mesa_glsl_parse_state *state)
@@ -162,6 +197,20 @@ _mesa_ast_to_hir(exec_list *instructions, struct
_mesa_glsl_parse_state *state)
*/
remove_per_vertex_blocks(instructions, state, ir_var_shader_in);
remove_per_vertex_blocks(instructions, state, ir_var_shader_out);
+
+ /* Check that we don't have reads from write-only variables */
+ read_from_write_only_variable_visitor v;
+ v.run(instructions);
+ ir_variable *error_var = v.get_variable();
+ if (error_var) {
+ /* It would be nice to have proper location information, but for that
+ * we would need to check this as we process each kind of AST node
+ */
+ YYLTYPE loc;
+ memset(&loc, 0, sizeof(loc));
+ _mesa_glsl_error(&loc, state, "Read from write-only variable `%s'",
+ error_var->name);
+ }
}
--
1.9.1
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