First implementation of store elimination.

test/mjsunit/compiler/store-elimination.js

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-// Flags: --allow-natives-syntax --load-elimination
+// Flags: --allow-natives-syntax --store-elimination
 
-// Test local load elimination of redundant loads and stores.
+// Test local elimination of unobservable stores.
 
 function B(x, y) {
   this.x = x;
   this.y = y;
   return this;
 }
 
-function test_params1(a, b) {
-  var i = a.x;
-  var j = a.x;
-  var k = b.x;
-  var l = b.x;
-  return i + j + k + l;
+function test_store_store() {
+  var a = new B(1, 2);
+  a.x = 3;  // eliminatable.
+  a.x = 4;
+  return a.x;
 }
 
-assertEquals(14, test_params1(new B(3, 4), new B(4, 5)));
-assertEquals(110, test_params1(new B(11, 7), new B(44, 8)));
-
-%OptimizeFunctionOnNextCall(test_params1);
-
-assertEquals(6, test_params1(new B(1, 7), new B(2, 8)));
-
-function test_params2(a, b) {
-  var o = new B(a + 1, b);
-  o.x = a;
-  var i = o.x;
-  o.x = a;
-  var j = o.x;
-  o.x = b;
-  var k = o.x;
-  o.x = b;
-  var l = o.x;
-  return i + j + k + l;
+function test_store_load_store1() {
+  var a = new B(6, 7);
+  a.x = 3;  // eliminatable.
+  var r = a.y;
+  a.x = 4;
+  return r;
 }
 
-assertEquals(14, test_params2(3, 4));
-assertEquals(110, test_params2(11, 44));
+function test_store_load_store2() {
+  var a = new B(6, 8);
+  a.x = 3;  // not eliminatable, unless next load is eliminated.
+  var r = a.x;
+  a.x = 4;
+  return r;
+}
 
-%OptimizeFunctionOnNextCall(test_params2);
+function test_store_call_store() {
+  var a = new B(2, 9);
+  a.x = 3;  // not eliminatable.
+  killall();
+  a.x = 4;
+  return a.y;
+}
 
-assertEquals(6, test_params2(1, 2));
+function test_store_deopt_store() {
+  var a = new B(2, 1);
+  a.x = 3;  // not eliminatable (implicit ValueOf following)
+  var c = a + 2;
+  a.x = 4;
+  return a.y;
+}
+
+function killall() {
+  try { } catch(e) { }
+}
+
+%NeverOptimizeFunction(killall);
+
+function test(x, f) {
+  assertEquals(x, f());
+  assertEquals(x, f());
+  %OptimizeFunctionOnNextCall(f);
+  assertEquals(x, f());
+}
+
+test(4, test_store_store);
+test(7, test_store_load_store1);
+test(3, test_store_load_store2);
+test(9, test_store_call_store);
+test(1, test_store_deopt_store);