1 files changed, 76 insertions, 0 deletions
diff --git a/src/glsl/ir_sub_to_add_neg.cpp b/src/glsl/ir_sub_to_add_neg.cpp
new file mode 100644
index 0000000000..7ed8c1495e
--- /dev/null
+++ b/src/glsl/ir_sub_to_add_neg.cpp
@@ -0,0 +1,76 @@
+/*
+ * 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_sub_to_add_neg.cpp
+ *
+ * Breaks an ir_binop_sub expression down to add(op0, neg(op1))
+ *
+ * This simplifies expression reassociation, and for many backends
+ * there is no subtract operation separate from adding the negation.
+ * For backends with native subtract operations, they will probably
+ * want to recognize add(op0, neg(op1)) or the other way around to
+ * produce a subtract anyway.
+ */
+
+#include "ir.h"
+
+class ir_sub_to_add_neg_visitor : public ir_hierarchical_visitor {
+public:
+   ir_sub_to_add_neg_visitor()
+   {
+      this->progress = false;
+   }
+
+   ir_visitor_status visit_leave(ir_expression *);
+
+   bool progress;
+};
+
+bool
+do_sub_to_add_neg(exec_list *instructions)
+{
+   ir_sub_to_add_neg_visitor v;
+
+   visit_list_elements(&v, instructions);
+   return v.progress;
+}
+
+ir_visitor_status
+ir_sub_to_add_neg_visitor::visit_leave(ir_expression *ir)
+{
+   if (ir->operation != ir_binop_sub)
+      return visit_continue;
+
+   void *mem_ctx = talloc_parent(ir);
+
+   ir->operation = ir_binop_add;
+   ir->operands[1] = new(mem_ctx) ir_expression(ir_unop_neg,
+						ir->operands[1]->type,
+						ir->operands[1],
+						NULL);
+
+   this->progress = true;
+
+   return visit_continue;
+}