https://gcc.gnu.org/bugzilla/show_bug.cgi?id=32605
Jed Brown <jed at 59A2 dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jed at 59A2 dot org
--- Comment #5 from Jed Brown <jed at 59A2 dot org> ---
The missed optimization even exists for code such as this, which should compile
to a simple load on LE architectures.
unsigned read_u32_le(const unsigned char arr[]) {
return (arr[0] << 0)
| (arr[1] << 8)
| (arr[2] << 16)
| (arr[3] << 24);
}
gcc-8.3/trunk -O:
read_u32_le:
movzx eax, BYTE PTR [rdi+1]
sal eax, 8
movzx edx, BYTE PTR [rdi+2]
sal edx, 16
or eax, edx
movzx edx, BYTE PTR [rdi]
or eax, edx
movzx edx, BYTE PTR [rdi+3]
sal edx, 24
or eax, edx
ret
clang-8 -O:
read_u32_le: # @read_u32_le
mov eax, dword ptr [rdi]
ret
https://gcc.godbolt.org/z/8lGeCF
