test/mjsunit/tail-call-intrinsic.js

// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Flags: --allow-natives-syntax --nostress-opt --turbo
// Flags: --nonative-context-specialization

var p0 = new Object();
var p1 = new Object();
var p2 = new Object();

// Ensure 1 parameter passed straight-through is handled correctly
var count1 = 100000;
tailee1 = function() {
  "use strict";
  if (count1-- == 0) {
    return this;
  }
  return %_TailCall(tailee1, this);
};

%OptimizeFunctionOnNextCall(tailee1);
assertEquals(p0, tailee1.call(p0));

// Ensure 2 parameters passed straight-through trigger a tail call are handled
// correctly and don't cause a stack overflow.
var count2 = 100000;
tailee2 = function(px) {
  "use strict";
  assertEquals(p2, px);
  assertEquals(p1, this);
  count2 = ((count2 | 0) - 1) | 0;
  if ((count2 | 0) === 0) {
    return this;
  }
  return %_TailCall(tailee2, this, px);
};

%OptimizeFunctionOnNextCall(tailee2);
assertEquals(p1, tailee2.call(p1, p2));

// Ensure swapped 2 parameters trigger a tail call and do the appropriate
// parameters swapping
var count3 = 999999;
tailee3 = function(px) {
  "use strict";
  if (count3-- == 0) {
    return this;
  }
  return %_TailCall(tailee3, px, this);
};

%OptimizeFunctionOnNextCall(tailee3);
assertEquals(p2, tailee3.call(p1, p2));

// Ensure too many parameters defeats the tail call optimization (currently
// unsupported).
var count4 = 1000000;
tailee4 = function(px) {
  "use strict";
  if (count4-- == 0) {
    return this;
  }
  return %_TailCall(tailee4, this, px, undefined);
};

%OptimizeFunctionOnNextCall(tailee4);
assertThrows(function() { tailee4.call(p1, p2); });

// Ensure that calling the arguments adapter defeats the tail call optimization.
var count5 = 1000000;
tailee5 = function(px) {
  "use strict";
  if (count5-- == 0) {
    return this;
  }
  return %_TailCall(tailee5, this);
};

%OptimizeFunctionOnNextCall(tailee5);
assertThrows(function() { tailee5.call(p1, p2); });

// Ensure tail calls with fewer stack parameters properly re-arranges the stack.
tailee6 = function(px) {
  return px;
}

tailee7 = function(px, py, pz, pa, pb, pc) {
  "use strict";
  return %_TailCall(tailee6, this, pc);
};

%OptimizeFunctionOnNextCall(tailee6);
%OptimizeFunctionOnNextCall(tailee7);
assertEquals(110, tailee7.call(null, 15, 16, 17, 18, 0, 110));

tailee8 = function(px, py, pz, pa, pb) {
  return pb + pz + px;
}

tailee9 = function(px, py, pz, pa, pb, pc) {
  "use strict";
  return %_TailCall(tailee8, this, pb, py, px, pa, pz);
};

%OptimizeFunctionOnNextCall(tailee8);
%OptimizeFunctionOnNextCall(tailee9);
assertEquals(32, tailee9.call(null, 15, 16, 17, 18, 0, 110));