1 // Copyright 2013 the V8 project authors. All rights reserved. 2 // Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved. 3 // 4 // Redistribution and use in source and binary forms, with or without 5 // modification, are permitted provided that the following conditions 6 // are met: 7 // 1. Redistributions of source code must retain the above copyright 8 // notice, this list of conditions and the following disclaimer. 9 // 2. Redistributions in binary form must reproduce the above copyright 10 // notice, this list of conditions and the following disclaimer in the 11 // documentation and/or other materials provided with the distribution. 12 // 13 // THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY 14 // EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 15 // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 16 // DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY 17 // DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 18 // (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 19 // LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON 20 // ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 22 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 24 description( 25 "This tests that a constant folding on a node that has obviously mispredicted type doesn't send the compiler into an infinite loop." 26 ); 27 28 // A function with an argument correctly predicted double. 29 function foo(x) { 30 // Two variables holding constants such that the bytecode generation constant folder 31 // will not constant fold the division below, but the DFG constant folder will. 32 var a = 1; 33 var b = 4000; 34 // A division that is going to be predicted integer on the first compilation. The 35 // compilation will be triggered from the loop below so the slow case counter of the 36 // division will be 1, which is too low for the division to be predicted double. 37 // If we constant fold this division, we'll have a constant node that is predicted 38 // integer but that contains a double. The subsequent addition to x, which is 39 // predicted double, will lead the Fixup phase to inject an Int32ToDouble node on 40 // the constant-that-was-a-division; subsequent fases in the fixpoint will constant 41 // fold that Int32ToDouble. And hence we will have an infinite loop. The correct fix 42 // is to disable constant folding of mispredicted nodes; that allows the normal 43 // process of correcting predictions (OSR exit profiling, exiting to profiled code, 44 // and recompilation with exponential backoff) to take effect so that the next 45 // compilation does not make this same mistake. 46 var c = (a / b) + x; 47 // A pointless loop to force the first compilation to occur before the division got 48 // hot. If this loop was not here then the division would be known to produce doubles 49 // on the first compilation. 50 var d = 0; 51 for (var i = 0; i < 1000; ++i) 52 d++; 53 return c + d; 54 } 55 56 // Call foo() enough times to make totally sure that we optimize. 57 for (var i = 0; i < 5; ++i) 58 shouldBe("foo(0.5)", "1000.50025"); 59
