1 files changed, 147 insertions, 0 deletions
diff --git a/src/glsl/opt_constant_folding.cpp b/src/glsl/opt_constant_folding.cpp
new file mode 100644
index 00000000000..554c54fae3a
--- /dev/null
+++ b/src/glsl/opt_constant_folding.cpp
@@ -0,0 +1,147 @@
+/*
+ * Copyright © 2010 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+/**
+ * \file ir_constant_folding.cpp
+ * Replace constant-valued expressions with references to constant values.
+ */
+
+#include "ir.h"
+#include "ir_visitor.h"
+#include "ir_rvalue_visitor.h"
+#include "ir_optimization.h"
+#include "glsl_types.h"
+
+/**
+ * Visitor class for replacing expressions with ir_constant values.
+ */
+
+class ir_constant_folding_visitor : public ir_rvalue_visitor {
+public:
+   ir_constant_folding_visitor()
+   {
+      this->progress = false;
+   }
+
+   virtual ~ir_constant_folding_visitor()
+   {
+      /* empty */
+   }
+
+   virtual ir_visitor_status visit_enter(ir_assignment *ir);
+   virtual ir_visitor_status visit_enter(ir_call *ir);
+
+   virtual void handle_rvalue(ir_rvalue **rvalue);
+
+   bool progress;
+};
+
+void
+ir_constant_folding_visitor::handle_rvalue(ir_rvalue **rvalue)
+{
+   if (*rvalue == NULL || (*rvalue)->ir_type == ir_type_constant)
+      return;
+
+   /* Note that we do rvalue visitoring on leaving.  So if an
+    * expression has a non-constant operand, no need to go looking
+    * down it to find if it's constant.  This cuts the time of this
+    * pass down drastically.
+    */
+   ir_expression *expr = (*rvalue)->as_expression();
+   if (expr) {
+      for (unsigned int i = 0; i < expr->get_num_operands(); i++) {
+	 if (!expr->operands[i]->as_constant())
+	    return;
+      }
+   }
+
+   ir_constant *constant = (*rvalue)->constant_expression_value();
+   if (constant) {
+      *rvalue = constant;
+      this->progress = true;
+   } else {
+      (*rvalue)->accept(this);
+   }
+}
+
+ir_visitor_status
+ir_constant_folding_visitor::visit_enter(ir_assignment *ir)
+{
+   ir->rhs->accept(this);
+   handle_rvalue(&ir->rhs);
+
+   if (ir->condition) {
+      ir->condition->accept(this);
+      handle_rvalue(&ir->condition);
+
+      ir_constant *const_val = ir->condition->as_constant();
+      /* If the condition is constant, either remove the condition or
+       * remove the never-executed assignment.
+       */
+      if (const_val) {
+	 if (const_val->value.b[0])
+	    ir->condition = NULL;
+	 else
+	    ir->remove();
+	 this->progress = true;
+      }
+   }
+
+   /* Don't descend into the LHS because we want it to stay as a
+    * variable dereference.  FINISHME: We probably should to get array
+    * indices though.
+    */
+   return visit_continue_with_parent;
+}
+
+ir_visitor_status
+ir_constant_folding_visitor::visit_enter(ir_call *ir)
+{
+   exec_list_iterator sig_iter = ir->get_callee()->parameters.iterator();
+   foreach_iter(exec_list_iterator, iter, *ir) {
+      ir_rvalue *param_rval = (ir_rvalue *)iter.get();
+      ir_variable *sig_param = (ir_variable *)sig_iter.get();
+
+      if (sig_param->mode == ir_var_in) {
+	 ir_rvalue *new_param = param_rval;
+
+	 handle_rvalue(&new_param);
+	 if (new_param != param_rval) {
+	    param_rval->replace_with(new_param);
+	 }
+      }
+      sig_iter.next();
+   }
+
+   return visit_continue_with_parent;
+}
+
+bool
+do_constant_folding(exec_list *instructions)
+{
+   ir_constant_folding_visitor constant_folding;
+
+   visit_list_elements(&constant_folding, instructions);
+
+   return constant_folding.progress;
+}