1 // Copyright 2012 the V8 project authors. All rights reserved. 2 // Redistribution and use in source and binary forms, with or without 3 // modification, are permitted provided that the following conditions are 4 // met: 5 // 6 // * Redistributions of source code must retain the above copyright 7 // notice, this list of conditions and the following disclaimer. 8 // * Redistributions in binary form must reproduce the above 9 // copyright notice, this list of conditions and the following 10 // disclaimer in the documentation and/or other materials provided 11 // with the distribution. 12 // * Neither the name of Google Inc. nor the names of its 13 // contributors may be used to endorse or promote products derived 14 // from this software without specific prior written permission. 15 // 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28 // Flags: --allow-natives-syntax 29 30 // The original problem from the bug: In the example below SMI check for b 31 // generated for inlining of equals invocation (marked with (*)) will be hoisted 32 // out of the loop across the typeof b === "object" condition and cause an 33 // immediate deopt. Another problem here is that no matter how many time we 34 // deopt and reopt we will continue to produce the wrong code. 35 // 36 // The fix is to notice when a deopt and subsequent reopt doesn't find 37 // additional type information, indicating that optimistic LICM should be 38 // disabled during compilation. 39 40 function eq(a, b) { 41 if (typeof b === "object") { 42 return b.equals(a); // (*) 43 } 44 return a === b; 45 } 46 47 Object.prototype.equals = function (other) { 48 return (this === other); 49 }; 50 51 function test() { 52 for (var i = 0; !eq(i, 10); i++) 53 ; 54 } 55 56 eq({}, {}); 57 eq({}, {}); 58 eq(1, 1); 59 eq(1, 1); 60 test(); 61 %OptimizeFunctionOnNextCall(test); 62 test(); 63 %OptimizeFunctionOnNextCall(test); 64 // Second compilation should have noticed that LICM wasn't a good idea, and now 65 // function should no longer deopt when called. 66 test(); 67 assertOptimized(test); 68
