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[libc++] Optimize the number of assignments in std::exclusive_scan 

Reported in https://twitter.com/blelbach/status/1169807347142676480

Differential Revision: https://reviews.llvm.org/D67273
This commit is contained in:
Louis Dionne 2020-11-24 12:29:08 -05:00
parent e0bf234930
commit c30d5101f1
1 changed files with 9 additions and 6 deletions
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15
libcxx/include/numeric
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@ -335,14 +335,17 @@ exclusive_scan(_InputIterator __first, _InputIterator __last,
{
if (__first != __last)
{
_Tp __saved = __init;
do
_Tp __tmp(__b(__init, *__first));
while (true)
{
__init = __b(__init, *__first);
*__result = __saved;
__saved = __init;
*__result = _VSTD::move(__init);
++__result;
} while (++__first != __last);
++__first;
if (__first == __last)
break;
__init = _VSTD::move(__tmp);
__tmp = __b(__init, *__first);
}
}
return __result;
}