Implement global load elimination based on flow engine.

test/mjsunit/compiler/load-elimination-global.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.
+// Test global load elimination of redundant loads and stores.
+
+var X = true;  // For forcing branches.
+X = false;
+X = true;
+X = false;
 
 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;
+  var f = a.x + a.x;
+  if (false) ;
+  return f + a.x + a.x;
+}
+
+function test_load2() {
+  var a = new B(1, 2);
+  var f = a.x + a.x;
+  if (true) ;
+  return f + 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;
+  var b = X ? a.x : a.x;
+  return b + a.x;
+}
+
+function test_store_load2() {
+  var a = new B(1, 2);
+  var c = 6;
+  if (X) a.x = c;
+  else a.x = c;
+  return a.x + a.x;
 }
 
 function test_nonaliasing_store1() {
   var a = new B(2, 3), b = new B(3, 4);
+  if (X) ;
   b.x = 4;
+  if (X) ;
   var f = a.x;
+  if (X) ;
   b.x = 5;
+  if (X) ;
   var g = a.x;
+  if (X) ;
   b.x = 6;
+  if (X) ;
   var h = a.x;
+  if (X) ;
   b.x = 7;
+  if (X) ;
   return f + g + h + a.x;
 }
 
+function test_loop(x) {
+  var a = new B(2, 3);
+  var v = a.x;
+  var total = v;
+  var i = 0;
+  while (i++ < 10) {
+    total = a.x;
+    a.y = 4;
+  }
+  return total;
+}
+
+function test_loop2(x) {
+  var a = new B(2, 3);
+  var v = a.x;
+  var total = v;
+  var i = 0;
+  while (i++ < 10) {
+    total = a.x;  // a.x not affected by loop
+    a.y = 4;
+
+    var j = 0;
+    while (j++ < 10) {
+      total = a.x;  // a.x not affected by loop
+      a.y = 5;
+    }
+
+    total = a.x;
+    a.y = 6;
+
+    j = 0;
+    while (j++ < 10) {
+      total = a.x;  // a.x not affected by loop
+      a.y = 7;
+    }
+  }
+  return total;
+}
+
 function killall() {
   try { } catch(e) { }
 }
 
 %NeverOptimizeFunction(killall);
 
 function test_store_load_kill() {
   var a = new B(1, 2);
+  if (X) ;
   a.x = 4;
+  if (X) ;
   var f = a.x;
+  if (X) ;
   a.x = 5;
+  if (X) ;
   var g = a.x;
+  if (X) ;
   killall();
+  if (X) ;
   a.x = 6;
+  if (X) ;
   var h = a.x;
+  if (X) ;
   a.x = 7;
+  if (X) ;
   return f + g + h + a.x;
 }
 
 function test_store_store() {
   var a = new B(6, 7);
+  if (X) ;
   a.x = 7;
+  if (X) ;
   a.x = 7;
+  if (X) ;
   a.x = 7;
+  if (X) ;
   a.x = 7;
+  if (X) ;
   return a.x;
 }
 
 function test(x, f) {
+  X = true;
   assertEquals(x, f());
   assertEquals(x, f());
+  X = false;
+  assertEquals(x, f());
+  assertEquals(x, f());
+  X = true;
   %OptimizeFunctionOnNextCall(f);
   assertEquals(x, f());
+  assertEquals(x, f());
+  X = false;
+  assertEquals(x, f());
+  assertEquals(x, f());
 }
 
 test(4, test_load);
-test(22, test_store_load);
+test(8, test_store_load);
+test(12, test_store_load2);
 test(8, test_nonaliasing_store1);
 test(22, test_store_load_kill);
 test(7, test_store_store);
+test(2, test_loop);
+test(2, test_loop2);