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* [gcc r13-1738] libstdc++: Enhance branching in std::inplace_merge and std::stable_sort
@ 2022-07-18 20:44 Franथईois Dumont
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From: Franथईois Dumont @ 2022-07-18 20:44 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:63d182fb86e47323ac50d9368845d712e1f7da89
commit r13-1738-g63d182fb86e47323ac50d9368845d712e1f7da89
Author: François Dumont <fdumont@gcc.gnu.org>
Date: Thu Jan 21 19:30:47 2021 +0100
libstdc++: Enhance branching in std::inplace_merge and std::stable_sort
When we manage to allocate a buffer of the expected size we can simplify the code to
perform the expected algorithm.
libstdc++-v3/ChangeLog:
* include/bits/stl_algo.h
(__merge_adaptive): Adapt to merge only when buffer is large enough..
(__merge_adaptive_resize): New, adapt merge when buffer is too small.
(__inplace_merge): Adapt, use latter.
(__stable_sort_adaptive): Adapt to sort only when buffer is large enough.
(__stable_sort_adaptive_resize): New, adapt sort when buffer is too small.
(__stable_sort): Adapt, use latter.
Diff:
---
libstdc++-v3/include/bits/stl_algo.h | 104 +++++++++++++++++++++++------------
1 file changed, 68 insertions(+), 36 deletions(-)
diff --git a/libstdc++-v3/include/bits/stl_algo.h b/libstdc++-v3/include/bits/stl_algo.h
index 1d8ed4e5fa8..c6078054514 100644
--- a/libstdc++-v3/include/bits/stl_algo.h
+++ b/libstdc++-v3/include/bits/stl_algo.h
@@ -2390,28 +2390,42 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
}
/// This is a helper function for the merge routines.
- template<typename _BidirectionalIterator, typename _Distance,
+ template<typename _BidirectionalIterator, typename _Distance,
typename _Pointer, typename _Compare>
void
__merge_adaptive(_BidirectionalIterator __first,
_BidirectionalIterator __middle,
_BidirectionalIterator __last,
_Distance __len1, _Distance __len2,
- _Pointer __buffer, _Distance __buffer_size,
- _Compare __comp)
+ _Pointer __buffer, _Compare __comp)
{
- if (__len1 <= __len2 && __len1 <= __buffer_size)
+ if (__len1 <= __len2)
{
_Pointer __buffer_end = _GLIBCXX_MOVE3(__first, __middle, __buffer);
std::__move_merge_adaptive(__buffer, __buffer_end, __middle, __last,
__first, __comp);
}
- else if (__len2 <= __buffer_size)
+ else
{
_Pointer __buffer_end = _GLIBCXX_MOVE3(__middle, __last, __buffer);
std::__move_merge_adaptive_backward(__first, __middle, __buffer,
__buffer_end, __last, __comp);
}
+ }
+
+ template<typename _BidirectionalIterator, typename _Distance,
+ typename _Pointer, typename _Compare>
+ void
+ __merge_adaptive_resize(_BidirectionalIterator __first,
+ _BidirectionalIterator __middle,
+ _BidirectionalIterator __last,
+ _Distance __len1, _Distance __len2,
+ _Pointer __buffer, _Distance __buffer_size,
+ _Compare __comp)
+ {
+ if (__len1 <= __buffer_size || __len2 <= __buffer_size)
+ std::__merge_adaptive(__first, __middle, __last,
+ __len1, __len2, __buffer, __comp);
else
{
_BidirectionalIterator __first_cut = __first;
@@ -2439,14 +2453,14 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
_BidirectionalIterator __new_middle
= std::__rotate_adaptive(__first_cut, __middle, __second_cut,
- __len1 - __len11, __len22, __buffer,
- __buffer_size);
- std::__merge_adaptive(__first, __first_cut, __new_middle, __len11,
- __len22, __buffer, __buffer_size, __comp);
- std::__merge_adaptive(__new_middle, __second_cut, __last,
- __len1 - __len11,
- __len2 - __len22, __buffer,
- __buffer_size, __comp);
+ __len1 - __len11, __len22,
+ __buffer, __buffer_size);
+ std::__merge_adaptive_resize(__first, __first_cut, __new_middle,
+ __len11, __len22,
+ __buffer, __buffer_size, __comp);
+ std::__merge_adaptive_resize(__new_middle, __second_cut, __last,
+ __len1 - __len11, __len2 - __len22,
+ __buffer, __buffer_size, __comp);
}
}
@@ -2524,11 +2538,14 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
// [first,middle) and [middle,last).
_TmpBuf __buf(__first, std::min(__len1, __len2));
- if (__buf.begin() == 0)
+ if (__builtin_expect(__buf.size() == __buf.requested_size(), true))
+ std::__merge_adaptive
+ (__first, __middle, __last, __len1, __len2, __buf.begin(), __comp);
+ else if (__builtin_expect(__buf.begin() == 0, false))
std::__merge_without_buffer
(__first, __middle, __last, __len1, __len2, __comp);
else
- std::__merge_adaptive
+ std::__merge_adaptive_resize
(__first, __middle, __last, __len1, __len2, __buf.begin(),
_DistanceType(__buf.size()), __comp);
}
@@ -2709,34 +2726,46 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
}
}
- template<typename _RandomAccessIterator, typename _Pointer,
- typename _Distance, typename _Compare>
+ template<typename _RandomAccessIterator, typename _Pointer, typename _Compare>
void
__stable_sort_adaptive(_RandomAccessIterator __first,
+ _RandomAccessIterator __middle,
_RandomAccessIterator __last,
- _Pointer __buffer, _Distance __buffer_size,
- _Compare __comp)
+ _Pointer __buffer, _Compare __comp)
+ {
+ std::__merge_sort_with_buffer(__first, __middle, __buffer, __comp);
+ std::__merge_sort_with_buffer(__middle, __last, __buffer, __comp);
+
+ std::__merge_adaptive(__first, __middle, __last,
+ __middle - __first, __last - __middle,
+ __buffer, __comp);
+ }
+
+ template<typename _RandomAccessIterator, typename _Pointer,
+ typename _Distance, typename _Compare>
+ void
+ __stable_sort_adaptive_resize(_RandomAccessIterator __first,
+ _RandomAccessIterator __last,
+ _Pointer __buffer, _Distance __buffer_size,
+ _Compare __comp)
{
const _Distance __len = (__last - __first + 1) / 2;
const _RandomAccessIterator __middle = __first + __len;
if (__len > __buffer_size)
{
- std::__stable_sort_adaptive(__first, __middle, __buffer,
- __buffer_size, __comp);
- std::__stable_sort_adaptive(__middle, __last, __buffer,
- __buffer_size, __comp);
+ std::__stable_sort_adaptive_resize(__first, __middle, __buffer,
+ __buffer_size, __comp);
+ std::__stable_sort_adaptive_resize(__middle, __last, __buffer,
+ __buffer_size, __comp);
+ std::__merge_adaptive_resize(__first, __middle, __last,
+ _Distance(__middle - __first),
+ _Distance(__last - __middle),
+ __buffer, __buffer_size,
+ __comp);
}
else
- {
- std::__merge_sort_with_buffer(__first, __middle, __buffer, __comp);
- std::__merge_sort_with_buffer(__middle, __last, __buffer, __comp);
- }
-
- std::__merge_adaptive(__first, __middle, __last,
- _Distance(__middle - __first),
- _Distance(__last - __middle),
- __buffer, __buffer_size,
- __comp);
+ std::__stable_sort_adaptive(__first, __middle, __last,
+ __buffer, __comp);
}
/// This is a helper function for the stable sorting routines.
@@ -4996,11 +5025,14 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
// so the buffer only needs to fit half the range at once.
_TmpBuf __buf(__first, (__last - __first + 1) / 2);
- if (__buf.begin() == 0)
+ if (__builtin_expect(__buf.requested_size() == __buf.size(), true))
+ std::__stable_sort_adaptive(__first, __first + __buf.size(), __last,
+ __buf.begin(), __comp);
+ else if (__builtin_expect(__buf.begin() == 0, false))
std::__inplace_stable_sort(__first, __last, __comp);
else
- std::__stable_sort_adaptive(__first, __last, __buf.begin(),
- _DistanceType(__buf.size()), __comp);
+ std::__stable_sort_adaptive_resize(__first, __last, __buf.begin(),
+ _DistanceType(__buf.size()), __comp);
}
/**
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