Implement global load elimination based on flow engine.

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

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-var steps = 100000;
-var undefined_values = [undefined, "go on"];
-var null_values = [null, "go on"];
+// Flags: --allow-natives-syntax --load-elimination
 
-function get_undefined_object(i) {
-  return undefined_values[(i / steps) | 0];
+// Test global load elimination in the presence of OSR compilation.
+
+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 test_undefined() {
-  var objects = 0;
-  for (var i = 0; i < 2 * steps; i++) {
-    undefined == get_undefined_object(i) && objects++;
+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 objects;
+
+  return o.y;
 }
 
-assertEquals(steps, test_undefined());
-
-
-function get_null_object(i) {
-  return null_values[(i / steps) | 0];
-}
-
-function test_null() {
-  var objects = 0;
-  for (var i = 0; i < 2 * steps; i++) {
-    null == get_null_object(i) && objects++;
-  }
-  return objects;
-}
-
-assertEquals(steps, test_null());
+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));