Migrated several tests from blink to V8 repository.

test/webkit/dfg-constant-fold-misprediction.js

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+// 1.  Redistributions of source code must retain the above copyright
+//     notice, this list of conditions and the following disclaimer.
+// 2.  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.
+//
+// THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS 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 APPLE INC. OR ITS 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
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+description(
+"This tests that a constant folding on a node that has obviously mispredicted type doesn't send the compiler into an infinite loop."
+);
+
+// A function with an argument correctly predicted double.
+function foo(x) {
+    // Two variables holding constants such that the bytecode generation constant folder
+    // will not constant fold the division below, but the DFG constant folder will.
+    var a = 1;
+    var b = 4000;
+    // A division that is going to be predicted integer on the first compilation. The
+    // compilation will be triggered from the loop below so the slow case counter of the
+    // division will be 1, which is too low for the division to be predicted double.
+    // If we constant fold this division, we'll have a constant node that is predicted
+    // integer but that contains a double. The subsequent addition to x, which is
+    // predicted double, will lead the Fixup phase to inject an Int32ToDouble node on
+    // the constant-that-was-a-division; subsequent fases in the fixpoint will constant
+    // fold that Int32ToDouble. And hence we will have an infinite loop. The correct fix
+    // is to disable constant folding of mispredicted nodes; that allows the normal
+    // process of correcting predictions (OSR exit profiling, exiting to profiled code,
+    // and recompilation with exponential backoff) to take effect so that the next
+    // compilation does not make this same mistake.
+    var c = (a / b) + x;
+    // A pointless loop to force the first compilation to occur before the division got
+    // hot. If this loop was not here then the division would be known to produce doubles
+    // on the first compilation.
+    var d = 0;
+    for (var i = 0; i < 1000; ++i)
+        d++;
+    return c + d;
+}
+
+// Call foo() enough times to make totally sure that we optimize.
+for (var i = 0; i < 5; ++i)
+    shouldBe("foo(0.5)", "1000.50025");
+
+