v8/test/mjsunit/compiler/load-elimination-global.js

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

// 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);
  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 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) {
  %PrepareFunctionForOptimization(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(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);