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Roll back -ffast-math

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Summary:
@public

`-ffast-math` does not have measurable performance benefits.

By using `NaN` for *undefined* values again, we can squeeze `YGFloatOptional` into 32 bits.
This will also enable us to store `YGValue` (or a variant of it) in 32 bits.

Reviewed By: astreet

Differential Revision: D13403925

fbshipit-source-id: b13d026bf556f24ab4699e65fb450af13a70961b
This commit is contained in:
David Aurelio
2018-12-13 07:09:28 -08:00
committed by Facebook Github Bot
parent 8ab01fde6e
commit 9ddda3c630
7 changed files with 21 additions and 77 deletions
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30
java/com/facebook/yoga/YogaConstants.java
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@@ -1,35 +1,17 @@
/*
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the LICENSE
* file in the root directory of this source tree.
/**
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the LICENSE
* file in the root directory of this source tree.
*/
package com.facebook.yoga;
public class YogaConstants {
/**
* Large positive number signifies that the property(float) is undefined. Earlier we used to have
* YGundefined as NAN, but the downside of this is that we can't use -ffast-math compiler flag as
* it assumes all floating-point calculation involve and result into finite numbers. For more
* information regarding -ffast-math compiler flag in clang, have a look at
* https://clang.llvm.org/docs/UsersManual.html#cmdoption-ffast-math
*/
public static final float UNDEFINED = (float) (10E20);
public static final float UNDEFINED = Float.NaN;
public static boolean isUndefined(float value) {
// Value of a float in the case of it being not defined is 10.1E20. Earlier it used to be NAN,
// the benefit of which
// was that if NAN is involved in any mathematical expression the result was NAN. But since we
// want to have `-ffast-math`
// flag being used by compiler which assumes that the floating point values are not NAN and Inf,
// we represent YGUndefined as 10.1E20.
// But now if YGUndefined is involved in any mathematical operations this value(10.1E20) would
// change.
// So the following check makes sure that if the value is outside a range (-10E8, 10E8) then it
// is undefined.
return (Float.compare(value, (float) 10E8) >= 0 || Float.compare(value, (float) -10E8) <= 0);
return Float.compare(value, UNDEFINED) == 0;
}
public static boolean isUndefined(YogaValue value) {