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