CSE2410 Fall 2014 Bounce

// Copyright 2010 the V8 project authors. All rights reserved.

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//

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// Flags: --always-opt --nocompilation-cache

// Given a binary operation string and an ordered array of leaf

// strings, return an array of all binary tree strings with the leaves

// (in order) as the fringe.

function makeTrees(op, leaves) {

  var len = leaves.length;

  if (len == 1) {

    // One leaf is a leaf.

    return leaves;

  } else {

    // More than one leaf requires an interior node.

    var result = [];

    // Split the leaves into left and right subtrees in all possible

    // ways.  For each split recursively compute all possible subtrees.

    for (var i = 1; i < len; ++i) {

      var leftTrees = makeTrees(op, leaves.slice(0, i));

      var rightTrees = makeTrees(op, leaves.slice(i, len));

      // Adjoin every possible left and right subtree.

      for (var j = 0; j < leftTrees.length; ++j) {

        for (var k = 0; k < rightTrees.length; ++k) {

          var string = "(" + leftTrees[j] + op + rightTrees[k] + ")";

          result.push(string);

        }

      }

    }

    return result;

  }

}

// All possible bitwise OR trees with six leaves, i.e. CatalanNumber[5] = 42,

// see http://mathworld.wolfram.com/CatalanNumber.html.

var identifiers = ['a','b','c','d','e','f'];

var or_trees = makeTrees("|", identifiers);

var and_trees = makeTrees("&", identifiers);

// Set up leaf masks to set 6 least-significant bits.

var a = 1 << 0;

var b = 1 << 1;

var c = 1 << 2;

var d = 1 << 3;

var e = 1 << 4;

var f = 1 << 5;

for (var i = 0; i < or_trees.length; ++i) {

  for (var j = 0; j < 6; ++j) {

    var or_fun = new Function("return " + or_trees[i]);

    if (j == 0) assertEquals(63, or_fun());

    // Set the j'th variable to a string to force a bailout.

    eval(identifiers[j] + "+= ''");

    assertEquals(63, or_fun());

    // Set it back to a number for the next iteration.

    eval(identifiers[j] + "= +" + identifiers[j]);

  }

}

// Set up leaf masks to clear 6 least-significant bits.

a ^= 63;

b ^= 63;

c ^= 63;

d ^= 63;

e ^= 63;

f ^= 63;

for (i = 0; i < and_trees.length; ++i) {

  for (var j = 0; j < 6; ++j) {

    var and_fun = new Function("return " + and_trees[i]);

    if (j == 0) assertEquals(0, and_fun());

    // Set the j'th variable to a string to force a bailout.

    eval(identifiers[j] + "+= ''");

    assertEquals(0, and_fun());

    // Set it back to a number for the next iteration.

    eval(identifiers[j] + "= +" + identifiers[j]);

  }

}