src/v8/test/mjsunit/compiler/store-elimination.js

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// Flags: --allow-natives-syntax --store-elimination

// Test local elimination of unobservable stores.

function B(x, y) {
  this.x = x;
  this.y = y;
  return this;
}

function test_store_store() {
  var a = new B(1, 2);
  a.x = 3;  // eliminatable.
  a.x = 4;
  return a.x;
}

function test_store_load_store1() {
  var a = new B(6, 7);
  a.x = 3;  // eliminatable.
  var r = a.y;
  a.x = 4;
  return r;
}

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;
}

function test_store_call_store() {
  var a = new B(2, 9);
  a.x = 3;  // not eliminatable.
  killall();
  a.x = 4;
  return a.y;
}

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) {
  %PrepareFunctionForOptimization(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);