From 8f2214f4892acb994d13531d555196bd8f242dad Mon Sep 17 00:00:00 2001
From: Ian Romanick <ian.d.romanick@intel.com>
Date: Mon, 13 Sep 2010 14:25:26 -0700
Subject: glsl2: Add pass to remove redundant jumps

---
 src/glsl/opt_redundant_jumps.cpp | 111 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 src/glsl/opt_redundant_jumps.cpp

(limited to 'src/glsl/opt_redundant_jumps.cpp')

diff --git a/src/glsl/opt_redundant_jumps.cpp b/src/glsl/opt_redundant_jumps.cpp
new file mode 100644
index 0000000000..edf4bb6c22
--- /dev/null
+++ b/src/glsl/opt_redundant_jumps.cpp
@@ -0,0 +1,111 @@
+/*
+ * 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 opt_redundant_jumps.cpp
+ * Remove certain types of redundant jumps
+ */
+
+#include "ir.h"
+
+class redundant_jumps_visitor : public ir_hierarchical_visitor {
+public:
+   redundant_jumps_visitor()
+   {
+      this->progress = false;
+   }
+
+   virtual ir_visitor_status visit_leave(ir_if *);
+   virtual ir_visitor_status visit_leave(ir_loop *);
+
+   bool progress;
+};
+
+
+ir_visitor_status
+redundant_jumps_visitor::visit_leave(ir_if *ir)
+{
+   /* If the last instruction in both branches is a 'break' or a 'continue',
+    * pull it out of the branches and insert it after the if-statment.  Note
+    * that both must be the same type (either 'break' or 'continue').
+    */
+   ir_instruction *const last_then =
+      (ir_instruction *) ir->then_instructions.get_tail();
+   ir_instruction *const last_else =
+      (ir_instruction *) ir->else_instructions.get_tail();
+
+   if ((last_then == NULL) || (last_else == NULL))
+      return visit_continue;
+
+   if ((last_then->ir_type != ir_type_loop_jump)
+       || (last_else->ir_type != ir_type_loop_jump))
+      return visit_continue;
+
+   ir_loop_jump *const then_jump = (ir_loop_jump *) last_then;
+   ir_loop_jump *const else_jump = (ir_loop_jump *) last_else;
+
+   if (then_jump->mode != else_jump->mode)
+      return visit_continue;
+
+   then_jump->remove();
+   else_jump->remove();
+   this->progress = true;
+
+   ir->insert_after(then_jump);
+
+   /* If both branchs of the if-statement are now empty, remove the
+    * if-statement.
+    */
+   if (ir->then_instructions.is_empty() && ir->else_instructions.is_empty())
+      ir->remove();
+
+   return visit_continue;
+}
+
+
+ir_visitor_status
+redundant_jumps_visitor::visit_leave(ir_loop *ir)
+{
+   /* If the last instruction of a loop body is a 'continue', remove it.
+    */
+   ir_instruction *const last =
+      (ir_instruction *) ir->body_instructions.get_tail();
+
+   if (last && (last->ir_type == ir_type_loop_jump)
+       && (((ir_loop_jump *) last)->mode == ir_loop_jump::jump_continue)) {
+      last->remove();
+      this->progress = true;
+   }
+
+   return visit_continue;
+}
+
+
+bool
+optimize_redundant_jumps(exec_list *instructions)
+{
+   redundant_jumps_visitor v;
+
+   v.run(instructions);
+   return v.progress;
+}
-- 
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