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libstdc++: Move code after an early exit constexpr if to under an else branch

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This avoids instantiating dead code when the true branch of the constexpr if is
taken.

libstdc++-v3/ChangeLog:

	* include/bits/ranges_algo.h (__lexicographical_compare_fn::operator()):
	Move code after an early exit constexpr if to under an else branch.
	* include/bits/ranges_algobase.h (__equal_fn::operator()): Likewise.
This commit is contained in:
Patrick Palka 2020-02-15 10:59:36 -05:00
parent e19c49e0da
commit 93b8cfce27
3 changed files with 66 additions and 60 deletions
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6
libstdc++-v3/ChangeLog
View file

@ -1,3 +1,9 @@
2020-02-16 Patrick Palka <ppalka@redhat.com>
* include/bits/ranges_algo.h (__lexicographical_compare_fn::operator()):
Move code after an early exit constexpr if to under an else branch.
* include/bits/ranges_algobase.h (__equal_fn::operator()): Likewise.
2020-02-15 Patrick Palka <ppalka@redhat.com>
* include/bits/ranges_algo.h: Adjust whitespace and formatting.

113
libstdc++-v3/include/bits/ranges_algo.h
View file

@ -3318,65 +3318,68 @@ namespace ranges
std::__niter_base(std::move(__last2)),
std::move(__comp),
std::move(__proj1), std::move(__proj2));
constexpr bool __sized_iters
= (sized_sentinel_for<_Sent1, _Iter1>
&& sized_sentinel_for<_Sent2, _Iter2>);
if constexpr (__sized_iters)
else
{
auto __d1 = ranges::distance(__first1, __last1);
auto __d2 = ranges::distance(__first2, __last2);
using _ValueType1 = iter_value_t<_Iter1>;
using _ValueType2 = iter_value_t<_Iter2>;
constexpr bool __use_memcmp
= ((is_integral_v<_ValueType1> || is_pointer_v<_ValueType1>)
&& is_same_v<_ValueType1, _ValueType2>
&& is_pointer_v<_Iter1>
&& is_pointer_v<_Iter2>
&& (is_same_v<_Comp, ranges::less>
|| is_same_v<_Comp, ranges::greater>)
&& is_same_v<_Proj1, identity>
&& is_same_v<_Proj2, identity>);
if constexpr (__use_memcmp)
constexpr bool __sized_iters
= (sized_sentinel_for<_Sent1, _Iter1>
&& sized_sentinel_for<_Sent2, _Iter2>);
if constexpr (__sized_iters)
{
if (const auto __len = std::min(__d1, __d2))
{
const auto __c = std::__memcmp(__first1, __first2, __len);
if constexpr (is_same_v<_Comp, ranges::less>)
{
if (__c < 0)
return true;
if (__c > 0)
return false;
}
else if constexpr (is_same_v<_Comp, ranges::greater>)
{
if (__c > 0)
return true;
if (__c < 0)
return false;
}
else
__builtin_unreachable();
}
return (__last1 - __first1 < __last2 - __first2);
}
}
auto __d1 = ranges::distance(__first1, __last1);
auto __d2 = ranges::distance(__first2, __last2);
for (; __first1 != __last1 && __first2 != __last2;
++__first1, (void) ++__first2)
{
if (std::__invoke(__comp,
std::__invoke(__proj1, *__first1),
std::__invoke(__proj2, *__first2)))
return true;
if (std::__invoke(__comp,
std::__invoke(__proj2, *__first2),
std::__invoke(__proj1, *__first1)))
return false;
using _ValueType1 = iter_value_t<_Iter1>;
using _ValueType2 = iter_value_t<_Iter2>;
constexpr bool __use_memcmp
= ((is_integral_v<_ValueType1> || is_pointer_v<_ValueType1>)
&& is_same_v<_ValueType1, _ValueType2>
&& is_pointer_v<_Iter1>
&& is_pointer_v<_Iter2>
&& (is_same_v<_Comp, ranges::less>
|| is_same_v<_Comp, ranges::greater>)
&& is_same_v<_Proj1, identity>
&& is_same_v<_Proj2, identity>);
if constexpr (__use_memcmp)
{
if (const auto __len = std::min(__d1, __d2))
{
const auto __c
= std::__memcmp(__first1, __first2, __len);
if constexpr (is_same_v<_Comp, ranges::less>)
{
if (__c < 0)
return true;
if (__c > 0)
return false;
}
else if constexpr (is_same_v<_Comp, ranges::greater>)
{
if (__c > 0)
return true;
if (__c < 0)
return false;
}
else
__builtin_unreachable();
}
return (__last1 - __first1 < __last2 - __first2);
}
}
for (; __first1 != __last1 && __first2 != __last2;
++__first1, (void) ++__first2)
{
if (std::__invoke(__comp,
std::__invoke(__proj1, *__first1),
std::__invoke(__proj2, *__first2)))
return true;
if (std::__invoke(__comp,
std::__invoke(__proj2, *__first2),
std::__invoke(__proj1, *__first1)))
return false;
}
return __first1 == __last1 && __first2 != __last2;
}
return __first1 == __last1 && __first2 != __last2;
}
template<input_range _Range1, input_range _Range2,

7
libstdc++-v3/include/bits/ranges_algobase.h
View file

@ -93,11 +93,8 @@ namespace ranges
std::__niter_base(std::move(__last2)),
std::move(__pred),
std::move(__proj1), std::move(__proj2));
constexpr bool __sized_iters
= (sized_sentinel_for<_Sent1, _Iter1>
&& sized_sentinel_for<_Sent2, _Iter2>);
if constexpr (__sized_iters)
else if constexpr (sized_sentinel_for<_Sent1, _Iter1>
&& sized_sentinel_for<_Sent2, _Iter2>)
{
auto __d1 = ranges::distance(__first1, __last1);
auto __d2 = ranges::distance(__first2, __last2);