================ @@ -41,13 +42,12 @@ _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 boo return true; } -template < - class _Tp, - class _Up, - class _BinaryPredicate, - __enable_if_t<__is_trivial_equality_predicate<_BinaryPredicate, _Tp, _Up>::value && !is_volatile<_Tp>::value && - !is_volatile<_Up>::value && __libcpp_is_trivially_equality_comparable<_Tp, _Up>::value, - int> = 0> +template < class _Tp, + class _Up, + class _BinaryPredicate, + __enable_if_t<__desugars_to<_BinaryPredicate, equal_to<_Tp> >::value && !is_volatile<_Tp>::value && ---------------- ldionne wrote:
I think it is pretty important to say `__desugars_to<_BinaryPredicate, equal_to<void> >::value` here. `equal_to<void>` represents the "transparent" version of `equal_to`, i.e. the one that does `x == y` without any conversion involved. If you use `__desugars_to<_BinaryPredicate, equal_to<_Tp> >::value`, it means that if `_Up` and `_Tp` are different but they happen to be trivially equality-comparable, we would skip this optimization. You should be able to check that this optimization gets disabled if you use something like [this](https://godbolt.org/z/hGq57j5jM): ``` #include <algorithm> using T = int*; using U = void*; bool f(T* first1, T* last1, U* first2, U* last2) { return std::equal(first1, last1, first2); } ``` ``` f(int**, int**, void**, void**): # @f(int**, int**, void**, void**) push rax mov rax, rsi sub rax, rdi mov rsi, rdx mov rdx, rax call bcmp@PLT test eax, eax sete al pop rcx ret ``` This is good, if there's no `bcmp` or `memcmp` in the output then the optimization was disabled. Since we don't have access to FileCheck in the libc++ test suite, however, it's going to be really hard to add a test for this. But it would be great if you can validate it manually at least. You can do something like this: ``` ninja -C build cxx-test-depends cat <<EOF | clang++ -xc++ - -nostdinc++ -isystem build/default/include/c++/v1 -std=c++17 -S -o a.s -O3 && cat a.s #include <algorithm> using T = int*; using U = void*; bool f(T* first1, T* last1, U* first2, U* last2) { return std::equal(first1, last1, first2); } EOF ``` https://github.com/llvm/llvm-project/pull/68642 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
