Implement local load/store elimination on basic blocks.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/24117004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16776 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -254,6 +254,7 @@ DEFINE_bool(trace_hydrogen_stubs, false, "trace generated hydrogen for stubs")
 DEFINE_string(trace_hydrogen_file, NULL, "trace hydrogen to given file name")
 DEFINE_string(trace_phase, "HLZ", "trace generated IR for specified phases")
 DEFINE_bool(trace_inlining, false, "trace inlining decisions")
+DEFINE_bool(trace_load_elimination, false, "trace load elimination")
 DEFINE_bool(trace_alloc, false, "trace register allocator")
 DEFINE_bool(trace_all_uses, false, "trace all use positions")
 DEFINE_bool(trace_range, false, "trace range analysis")
@@ -288,6 +289,7 @@ DEFINE_bool(array_index_dehoisting, true,
             "perform array index dehoisting")
 DEFINE_bool(analyze_environment_liveness, true,
             "analyze liveness of environment slots and zap dead values")
+DEFINE_bool(load_elimination, false, "use load elimination")
 DEFINE_bool(dead_code_elimination, true, "use dead code elimination")
 DEFINE_bool(fold_constants, true, "use constant folding")
 DEFINE_bool(trace_dead_code_elimination, false, "trace dead code elimination")

src/hydrogen-load-elimination.h

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_HYDROGEN_LOAD_ELIMINATION_H_
+#define V8_HYDROGEN_LOAD_ELIMINATION_H_
+
+#include "hydrogen.h"
+
+namespace v8 {
+namespace internal {
+
+class HLoadEliminationPhase : public HPhase {
+ public:
+  explicit HLoadEliminationPhase(HGraph* graph)
+      : HPhase("H_Load elimination", graph) { }
+
+  void Run();
+
+ private:
+  void EliminateLoads(HBasicBlock* block);
+};
+
+
+} }  // namespace v8::internal
+
+#endif  // V8_HYDROGEN_LOAD_ELIMINATION_H_

src/hydrogen.cc

@@ -43,6 +43,7 @@
 #include "hydrogen-escape-analysis.h"
 #include "hydrogen-infer-representation.h"
 #include "hydrogen-infer-types.h"
+#include "hydrogen-load-elimination.h"
 #include "hydrogen-gvn.h"
 #include "hydrogen-mark-deoptimize.h"
 #include "hydrogen-minus-zero.h"
@@ -2971,6 +2972,8 @@ bool HGraph::Optimize(BailoutReason* bailout_reason) {
 
   if (FLAG_use_escape_analysis) Run<HEscapeAnalysisPhase>();
 
+  if (FLAG_load_elimination) Run<HLoadEliminationPhase>();
+
   CollectPhis();
 
   if (has_osr()) osr()->FinishOsrValues();

test/mjsunit/compiler/load-elimination.js

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax --load-elimination
+
+// Test local load elimination of redundant loads and stores.
+
+function B(x, y) {
+  this.x = x;
+  this.y = y;
+  return this;
+}
+
+function test_load() {
+  var a = new B(1, 2);
+  return a.x + a.x + a.x + a.x;
+}
+
+function test_store_load() {
+  var a = new B(1, 2);
+  a.x = 4;
+  var f = a.x;
+  a.x = 5;
+  var g = a.x;
+  a.x = 6;
+  var h = a.x;
+  a.x = 7;
+  return f + g + h + a.x;
+}
+
+function test_nonaliasing_store1() {
+  var a = new B(2, 3), b = new B(3, 4);
+  b.x = 4;
+  var f = a.x;
+  b.x = 5;
+  var g = a.x;
+  b.x = 6;
+  var h = a.x;
+  b.x = 7;
+  return f + g + h + a.x;
+}
+
+function killall() {
+  try { } catch(e) { }
+}
+
+%NeverOptimizeFunction(killall);
+
+function test_store_load_kill() {
+  var a = new B(1, 2);
+  a.x = 4;
+  var f = a.x;
+  a.x = 5;
+  var g = a.x;
+  killall();
+  a.x = 6;
+  var h = a.x;
+  a.x = 7;
+  return f + g + h + a.x;
+}
+
+function test_store_store() {
+  var a = new B(6, 7);
+  a.x = 7;
+  a.x = 7;
+  a.x = 7;
+  a.x = 7;
+  return a.x;
+}
+
+function test(x, f) {
+  assertEquals(x, f());
+  assertEquals(x, f());
+  %OptimizeFunctionOnNextCall(f);
+  assertEquals(x, f());
+}
+
+test(4, test_load);
+test(22, test_store_load);
+test(8, test_nonaliasing_store1);
+test(22, test_store_load_kill);
+test(7, test_store_store);

tools/gyp/v8.gyp

@@ -353,6 +353,8 @@
         '../../src/hydrogen-infer-representation.h',
         '../../src/hydrogen-infer-types.cc',
         '../../src/hydrogen-infer-types.h',
+        '../../src/hydrogen-load-elimination.cc',
+        '../../src/hydrogen-load-elimination.h',
         '../../src/hydrogen-mark-deoptimize.cc',
         '../../src/hydrogen-mark-deoptimize.h',
         '../../src/hydrogen-minus-zero.cc',