[libc++] Suboptimal codegen for std::equal(std::byte)

[halbi2]

#include <algorithm>
bool f(char* a, char* b) {
  return std::equal(a, a+16, b, b+16);
}
bool g(std::byte* a, std::byte* b) {
  return std::equal(a, a+16, b, b+16);
}

f generates pcmpeqb. g generates a loop. std::equal should be aware that std::byte is functionally the same as char.

#89820 could relate.

[philnik777]

std::equal isn't actually aware of char specifically. It's just aware that char is a trivially equality comparable type, which std::byte currently isn't. We'll have to fix that in the compiler.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (halbi2)

``` #include <algorithm> bool f(char* a, char* b) { return std::equal(a, a+16, b, b+16); } bool g(std::byte* a, std::byte* b) { return std::equal(a, a+16, b, b+16); } ``` `f` generates `pcmpeqb`. `g` generates a loop. `std::equal` should be aware that `std::byte` is functionally the same as `char`.

#89820 could relate.