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From: Aldy Hernandez <aldyh@gcc.gnu.org>
To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org
Subject: [gcc/devel/ranger] libstdc++: Move code after an early exit constexpr if to under an else branch
Date: Wed, 17 Jun 2020 18:55:08 +0000 (GMT) [thread overview]
Message-ID: <20200617185508.6BE393953421@sourceware.org> (raw)
https://gcc.gnu.org/g:93b8cfce27abe795f56ab467570f66682e9688ca
commit 93b8cfce27abe795f56ab467570f66682e9688ca
Author: Patrick Palka <ppalka@redhat.com>
Date: Sat Feb 15 10:59:36 2020 -0500
libstdc++: Move code after an early exit constexpr if to under an else branch
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.
Diff:
---
libstdc++-v3/ChangeLog | 6 ++
libstdc++-v3/include/bits/ranges_algo.h | 103 ++++++++++++++--------------
libstdc++-v3/include/bits/ranges_algobase.h | 7 +-
3 files changed, 61 insertions(+), 55 deletions(-)
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index b57ac9658e8..25fa9ba6098 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -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.
diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h
index 7f8f0fb964b..ff1b40f6ace 100644
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -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))
+ 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)
{
- 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 (const auto __len = std::min(__d1, __d2))
{
- if (__c > 0)
- return true;
- if (__c < 0)
- return false;
+ 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();
}
- else
- __builtin_unreachable();
+ return (__last1 - __first1 < __last2 - __first2);
}
- 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;
+ 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,
diff --git a/libstdc++-v3/include/bits/ranges_algobase.h b/libstdc++-v3/include/bits/ranges_algobase.h
index f8643b5a933..cc24483b2d3 100644
--- a/libstdc++-v3/include/bits/ranges_algobase.h
+++ b/libstdc++-v3/include/bits/ranges_algobase.h
@@ -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);
reply other threads:[~2020-06-17 18:55 UTC|newest]
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