src/v8/test/mjsunit/compiler/dead-loops.js

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// Flags: --allow-natives-syntax

// Presents opportunities for dead loop removal.

function loop1() {
  while (false) ;  // doesn't even loop.
}

function loop2() {
  var i = 0;
  while (i++ < 10) ;  // nothing in the body.
}

function loop3() {
  for (var i = 0; i < 10; i++) ;  // nothing in the body.
}

function loop4() {
  var a = 0;
  for (var i = 0; i < 10; i++) a++;  // {a} is dead after the loop.
}

function loop5() {
  var a = new Int32Array(4), sum = 0;
  for (var i = 0; i < a.length; i++) {
    // Involves only reads on typed arrays, and {i} doesn't overflow.
    sum += a[i];
  }
}

function loop6() {
  var a = new Array(4), sum = 0;
  for (var i = 0; i < a.length; i++) {
    // Involves only in-bounds read on the array {a}.
    // Have to prove that {a} doesn't have getters...?
    sum += a[i];
  }
}

function loop7() {
  for (var i = 0; i < 10; i++) {
    new Object();  // Have to prove the allocation doesn't escape.
  }
}

function loop8() {
  for (var i = 0; i < 10; i++) {
    var x = {};  // Have to prove the allocation doesn't escape.
  }
}

var loops = [loop1, loop2, loop3, loop4, loop5, loop6, loop7, loop8];

for (var i = 0; i < loops.length; i++) {
  var f = loops[i];
  %PrepareFunctionForOptimization(f);
  f();
  f();
  %OptimizeFunctionOnNextCall(f);
  f();
}