https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115497
--- Comment #18 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:b3743181899c5490a94c4dbde56a69ab77a40f11 commit r15-1549-gb3743181899c5490a94c4dbde56a69ab77a40f11 Author: Jonathan Wakely <jwak...@redhat.com> Date: Wed Jun 19 16:14:56 2024 +0100 libstdc++: Fix std::fill and std::fill_n optimizations [PR109150] As noted in the PR, the optimization used for scalar types in std::fill and std::fill_n is non-conforming, because it doesn't consider that assigning a scalar type might have non-trivial side effects which are affected by the optimization. By changing the condition under which the optimization is done we ensure it's only performed when safe to do so, and we also enable it for additional types, which was the original subject of the PR. Instead of two overloads using __enable_if<__is_scalar<T>::__value, R> we can combine them into one and create a local variable which is either a local copy of __value or another reference to it, depending on whether the optimization is allowed. This removes a use of std::__is_scalar, which is a step towards fixing PR 115497 by removing std::__is_pointer from <bits/cpp_type_traits.h> libstdc++-v3/ChangeLog: PR libstdc++/109150 * include/bits/stl_algobase.h (__fill_a1): Combine the !__is_scalar and __is_scalar overloads into one and rewrite the condition used to decide whether to perform the load outside the loop. * testsuite/25_algorithms/fill/109150.cc: New test. * testsuite/25_algorithms/fill_n/109150.cc: New test.
