v8/test/mjsunit/unary-minus-deopt.js
svenpanne@chromium.org bf71023ba5 Replaced unary negation by multiplication with -1.
This fixes a deopt loop in the Epic Citadel demo and removes some code. Apart from that, this change is performance-neutral.

When we do something similar for BIT_NOT, the whole UnaryOp stuff can go away.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/21782002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16029 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
2013-08-02 11:56:35 +00:00

56 lines
2.4 KiB
JavaScript

// Copyright 2013 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// Flags: --allow-natives-syntax
// This is a boiled-down example happening in the Epic Citadel demo:
// After deopting, the multiplication for unary minus stayed in Smi
// mode instead of going to double mode, leading to deopt loops.
function unaryMinusTest(x) {
var g = (1 << x) | 0;
// Optimized code will contain a LMulI with -1 as right operand.
return (g & -g) - 1 | 0;
}
unaryMinusTest(3);
unaryMinusTest(3);
%OptimizeFunctionOnNextCall(unaryMinusTest);
unaryMinusTest(3);
assertOptimized(unaryMinusTest);
// Deopt on kMinInt
unaryMinusTest(31);
// The following is normally true, but not with --stress-opt. :-/
// assertUnoptimized(unaryMinusTest);
// We should have learned something from the deopt.
unaryMinusTest(31);
%OptimizeFunctionOnNextCall(unaryMinusTest);
unaryMinusTest(31);
assertOptimized(unaryMinusTest);