glsl2: Set a flag when visiting the assignee of an assignment

src/glsl/ir_hierarchical_visitor.cpp

@@ -29,6 +29,7 @@ ir_hierarchical_visitor::ir_hierarchical_visitor()
    this->base_ir = NULL;
    this->callback = NULL;
    this->data = NULL;
+   this->in_assignee = false;
 }
 
 ir_visitor_status

src/glsl/ir_hierarchical_visitor.h

@@ -165,6 +165,13 @@ public:
     * Extra data parameter passed to the per-node callback function
     */
    void *data;
+
+   /**
+    * Currently in the LHS of an assignment?
+    *
+    * This is set and cleared by the \c ir_assignment::accept method.
+    */
+   bool in_assignee;
 };
 
 void visit_tree(ir_instruction *ir,

src/glsl/ir_hv_accept.cpp

@@ -242,7 +242,14 @@ ir_dereference_array::accept(ir_hierarchical_visitor *v)
    if (s != visit_continue)
       return (s == visit_continue_with_parent) ? visit_continue : s;
 
+   /* The array index is not the target of the assignment, so clear the
+    * 'in_assignee' flag.  Restore it after returning from the array index.
+    */
+   const bool was_in_assignee = v->in_assignee;
+   v->in_assignee = false;
    s = this->array_index->accept(v);
+   v->in_assignee = was_in_assignee;
+
    if (s != visit_continue)
       return (s == visit_continue_with_parent) ? visit_continue : s;
 
@@ -270,7 +277,9 @@ ir_assignment::accept(ir_hierarchical_visitor *v)
    if (s != visit_continue)
       return (s == visit_continue_with_parent) ? visit_continue : s;
 
+   v->in_assignee = true;
    s = this->lhs->accept(v);
+   v->in_assignee = false;
    if (s != visit_continue)
       return (s == visit_continue_with_parent) ? visit_continue : s;
 

src/glsl/ir_rvalue_visitor.cpp

@@ -83,7 +83,14 @@ ir_rvalue_visitor::visit_leave(ir_swizzle *ir)
 ir_visitor_status
 ir_rvalue_visitor::visit_leave(ir_dereference_array *ir)
 {
+   /* The array index is not the target of the assignment, so clear the
+    * 'in_assignee' flag.  Restore it after returning from the array index.
+    */
+   const bool was_in_assignee = this->in_assignee;
+   this->in_assignee = false;
    handle_rvalue(&ir->array_index);
+   this->in_assignee = was_in_assignee;
+
    handle_rvalue(&ir->array);
    return visit_continue;
 }