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[turbofan] Improve typing rule for NumberRound.

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This extends the typing rule for NumberRound to deal with general number
inputs properly, thus addressing a long-standing TODO. We also add test
cases to ensure that the typing rule gets the corner cases for NaN and
-0 right.

Bug: v8:5267, v8:7109
Change-Id: Ia865ec1d6f8d96f20641bee96891740a9fc6e627
Reviewed-on: https://chromium-review.googlesource.com/792931
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49651}
This commit is contained in:
Benedikt Meurer 2017-11-28 07:41:56 +01:00 committed by Commit Bot
parent c7742e4953
commit 71f3ab8e76
2 changed files with 42 additions and 2 deletions
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5
src/compiler/operation-typer.cc
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@ -418,8 +418,9 @@ Type* OperationTyper::NumberLog10(Type* type) {
Type* OperationTyper::NumberRound(Type* type) {
DCHECK(type->Is(Type::Number()));
if (type->Is(cache_.kIntegerOrMinusZeroOrNaN)) return type;
// TODO(bmeurer): We could infer a more precise type here.
return cache_.kIntegerOrMinusZeroOrNaN;
type = Type::Intersect(type, Type::NaN(), zone());
type = Type::Union(type, cache_.kIntegerOrMinusZero, zone());
return type;
}
Type* OperationTyper::NumberSign(Type* type) {

39
test/mjsunit/compiler/math-round.js Normal file
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@ -0,0 +1,39 @@
// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Flags: --allow-natives-syntax
// Ensure that the typing rule for Math.round deals correctly with
// inputs in the range [-0.5,0.0), which are mapped to -0.
(function() {
function foo(x) {
// Arrange x such that TurboFan infers type PlainNumber \/ NaN.
x = +x;
x = Math.abs(x) - 1.0;
return Object.is(-0, Math.round(x));
}
assertFalse(foo(1.5));
assertTrue(foo(0.5));
%OptimizeFunctionOnNextCall(foo);
assertFalse(foo(1.5));
assertTrue(foo(0.5));
})();
// Ensure that the typing rule for Math.round deals correctly with
// NaN inputs, which are mapped to NaN.
(function() {
function foo(x) {
// Arrange x such that TurboFan infers type PlainNumber \/ NaN.
x = +x;
x = Math.abs(x) - 1.0;
return Object.is(NaN, Math.round(x));
}
assertFalse(foo(1.5));
assertTrue(foo(NaN));
%OptimizeFunctionOnNextCall(foo);
assertFalse(foo(1.5));
assertTrue(foo(NaN));
})();