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libstdc++: Simplify chrono::duration::_S_gcd 

We can simplify this constexpr function further because we know that
period::num >= 1 and period::den >= 1 so only the remainder can ever be
zero.

libstdc++-v3/ChangeLog:

	* include/std/chrono (duration::_S_gcd): Use invariant that
	neither value is zero initially.
This commit is contained in:
Jonathan Wakely 2020-09-07 20:09:17 +01:00
parent 00ffe73007
commit ec5096f48b
1 changed files with 4 additions and 3 deletions
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7
libstdc++-v3/include/std/chrono
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@ -430,17 +430,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// Duration only allows positive periods so we don't need to
// handle negative values here (unlike __static_gcd and std::gcd).
#if __cplusplus >= 201402L
while (__m != 0 && __n != 0)
do
{
intmax_t __rem = __m % __n;
__m = __n;
__n = __rem;
}
return __m + __n;
while (__n != 0);
return __m;
#else
// C++11 doesn't allow loops in constexpr functions, but this
// recursive version can be more expensive to evaluate.
return (__m == 0) ? __n : (__n == 0) ? __m : _S_gcd(__n, __m % __n);
return (__n == 0) ? __m : _S_gcd(__n, __m % __n);
#endif
}