Fix load elimination: can only .Equals() GVN-able instructions.

test/mjsunit/compiler/load-elimination-params.js

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 // Flags: --allow-natives-syntax --load-elimination
 
-// Test global load elimination in the presence of OSR compilation.
+// Test local load elimination of redundant loads and stores.
 
-function It(x, y) { }
-
-function foo_osr(x, limit) {
-  var o = new It();
-  o.x = x;
-  o.y = x;
-  for (var i = 0; i < limit; i++) {
-    o.y += o.x;  // Load of x cannot be hoisted due to OSR.
-  }
-
-  return o.y;
+function B(x, y) {
+  this.x = x;
+  this.y = y;
+  return this;
 }
 
-assertEquals(22, foo_osr(11, 1));
-assertEquals(24, foo_osr(12, 1));
-assertEquals(1300013, foo_osr(13, 100000));
-
-
-function foo_hot(x, limit) {
-  var o = new It();
-  o.x = x;
-  o.y = x;
-  for (var i = 0; i < limit; i++) {
-    o.y += o.x;  // Load of x can be hoisted without OSR.
-  }
-
-  return o.y;
+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;
 }
 
-assertEquals(22, foo_hot(11, 1));
-assertEquals(24, foo_hot(12, 1));
-%OptimizeFunctionOnNextCall(foo_hot);
-assertEquals(32, foo_hot(16, 1));
-assertEquals(1300013, foo_hot(13, 100000));
+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;
+}
+
+assertEquals(14, test_params2(3, 4));
+assertEquals(110, test_params2(11, 44));
+
+%OptimizeFunctionOnNextCall(test_params2);
+
+assertEquals(6, test_params2(1, 2));