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author | Jonathan Wakely <jwakely@redhat.com> | 2021-11-24 13:17:54 +0000 |
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committer | Jonathan Wakely <jwakely@redhat.com> | 2021-11-25 20:03:13 +0000 |
commit | 82c3657dd74896b39937bb0a2aaeba9b8ca105fd (patch) | |
tree | 385489961fb54b92f450312d44bc35cd5abcc885 | |
parent | 6ea5fb3cc7f3cc9b731d72183c66c23543876f5a (diff) | |
download | gcc-82c3657dd74896b39937bb0a2aaeba9b8ca105fd.zip gcc-82c3657dd74896b39937bb0a2aaeba9b8ca105fd.tar.gz gcc-82c3657dd74896b39937bb0a2aaeba9b8ca105fd.tar.bz2 |
libstdc++: Do not use memset in constexpr calls to ranges::fill_n [PR101608]
libstdc++-v3/ChangeLog:
PR libstdc++/101608
* include/bits/ranges_algobase.h (__fill_n_fn): Check for
constant evaluation before using memset.
* testsuite/25_algorithms/fill_n/constrained.cc: Check
byte-sized values as well.
-rw-r--r-- | libstdc++-v3/include/bits/ranges_algobase.h | 28 | ||||
-rw-r--r-- | libstdc++-v3/testsuite/25_algorithms/fill_n/constrained.cc | 6 |
2 files changed, 22 insertions, 12 deletions
diff --git a/libstdc++-v3/include/bits/ranges_algobase.h b/libstdc++-v3/include/bits/ranges_algobase.h index c8c4d03..9929e5e 100644 --- a/libstdc++-v3/include/bits/ranges_algobase.h +++ b/libstdc++-v3/include/bits/ranges_algobase.h @@ -527,17 +527,25 @@ namespace ranges if (__n <= 0) return __first; - // TODO: Generalize this optimization to contiguous iterators. - if constexpr (is_pointer_v<_Out> - // Note that __is_byte already implies !is_volatile. - && __is_byte<remove_pointer_t<_Out>>::__value - && integral<_Tp>) - { - __builtin_memset(__first, static_cast<unsigned char>(__value), __n); - return __first + __n; - } - else if constexpr (is_scalar_v<_Tp>) + if constexpr (is_scalar_v<_Tp>) { + // TODO: Generalize this optimization to contiguous iterators. + if constexpr (is_pointer_v<_Out> + // Note that __is_byte already implies !is_volatile. + && __is_byte<remove_pointer_t<_Out>>::__value + && integral<_Tp>) + { +#ifdef __cpp_lib_is_constant_evaluated + if (!std::is_constant_evaluated()) +#endif + { + __builtin_memset(__first, + static_cast<unsigned char>(__value), + __n); + return __first + __n; + } + } + const auto __tmp = __value; for (; __n > 0; --__n, (void)++__first) *__first = __tmp; diff --git a/libstdc++-v3/testsuite/25_algorithms/fill_n/constrained.cc b/libstdc++-v3/testsuite/25_algorithms/fill_n/constrained.cc index 6a015d34..1d1e1c1 100644 --- a/libstdc++-v3/testsuite/25_algorithms/fill_n/constrained.cc +++ b/libstdc++-v3/testsuite/25_algorithms/fill_n/constrained.cc @@ -73,11 +73,12 @@ test01() } } +template<typename T> constexpr bool test02() { bool ok = true; - int x[6] = { 1, 2, 3, 4, 5, 6 }; + T x[6] = { 1, 2, 3, 4, 5, 6 }; const int y[6] = { 1, 2, 3, 4, 5, 6 }; const int z[6] = { 17, 17, 17, 4, 5, 6 }; @@ -94,5 +95,6 @@ int main() { test01(); - static_assert(test02()); + static_assert(test02<int>()); + static_assert(test02<unsigned char>()); // PR libstdc++/101608 } |