Mesa (master): glsl2: Add pass to remove redundant jumps

[Ian Romanick]

Module: Mesa
Branch: master
Commit: 8f2214f4892acb994d13531d555196bd8f242dad
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=8f2214f4892acb994d13531d555196bd8f242dad

Author: Ian Romanick <ian.d.romanick at intel.com>
Date:   Mon Sep 13 14:25:26 2010 -0700

glsl2: Add pass to remove redundant jumps

---

 src/glsl/Makefile                |    1 +
 src/glsl/Makefile.am             |    3 +-
 src/glsl/SConscript              |    1 +
 src/glsl/glsl_parser_extras.cpp  |    2 +
 src/glsl/ir_optimization.h       |    1 +
 src/glsl/opt_redundant_jumps.cpp |  111 ++++++++++++++++++++++++++++++++++++++
 6 files changed, 118 insertions(+), 1 deletions(-)

diff --git a/src/glsl/Makefile b/src/glsl/Makefile
index a0e7c05..1746e18 100644
--- a/src/glsl/Makefile
+++ b/src/glsl/Makefile
@@ -76,6 +76,7 @@ CXX_SOURCES = \
 	loop_controls.cpp \
 	loop_unroll.cpp \
 	lower_noise.cpp \
+	opt_redundant_jumps.cpp \
 	s_expression.cpp
 
 LIBS = \
diff --git a/src/glsl/Makefile.am b/src/glsl/Makefile.am
index 3ce8e21..f62a85e 100644
--- a/src/glsl/Makefile.am
+++ b/src/glsl/Makefile.am
@@ -66,7 +66,8 @@ glsl_SOURCES = \
 	loop_analysis.cpp \
 	loop_controls.cpp \
 	loop_unroll.cpp \
-	lower_noise.cpp
+	lower_noise.cpp \
+	opt_redundant_jumps.cpp
 
 BUILT_SOURCES = glsl_parser.h glsl_parser.cpp glsl_lexer.cpp
 CLEANFILES = $(BUILT_SOURCES)
diff --git a/src/glsl/SConscript b/src/glsl/SConscript
index bd324ee..6e2ef2d 100644
--- a/src/glsl/SConscript
+++ b/src/glsl/SConscript
@@ -73,6 +73,7 @@ sources = [
     'loop_controls.cpp',
     'loop_unroll.cpp',
     'lower_noise.cpp',
+    'opt_redundant_jumps.cpp',
     's_expression.cpp',
 ]
 
diff --git a/src/glsl/glsl_parser_extras.cpp b/src/glsl/glsl_parser_extras.cpp
index 28241f7..4ac062b 100644
--- a/src/glsl/glsl_parser_extras.cpp
+++ b/src/glsl/glsl_parser_extras.cpp
@@ -716,6 +716,8 @@ do_common_optimization(exec_list *ir, bool linked, unsigned max_unroll_iteration
    progress = do_swizzle_swizzle(ir) || progress;
    progress = do_noop_swizzle(ir) || progress;
 
+   progress = optimize_redundant_jumps(ir) || progress;
+
    loop_state *ls = analyze_loop_variables(ir);
    progress = set_loop_controls(ir, ls) || progress;
    progress = unroll_loops(ir, ls, max_unroll_iterations) || progress;
diff --git a/src/glsl/ir_optimization.h b/src/glsl/ir_optimization.h
index 726a6ad..b365ed2 100644
--- a/src/glsl/ir_optimization.h
+++ b/src/glsl/ir_optimization.h
@@ -56,3 +56,4 @@ bool do_tree_grafting(exec_list *instructions);
 bool do_vec_index_to_cond_assign(exec_list *instructions);
 bool do_vec_index_to_swizzle(exec_list *instructions);
 bool lower_noise(exec_list *instructions);
+bool optimize_redundant_jumps(exec_list *instructions);
diff --git a/src/glsl/opt_redundant_jumps.cpp b/src/glsl/opt_redundant_jumps.cpp
new file mode 100644
index 0000000..edf4bb6
--- /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;
+}