https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93328
Paco Arjonilla <pacoarjonilla at yahoo dot es> changed:
What |Removed |Added
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CC| |pacoarjonilla at yahoo dot es
--- Comment #2 from Paco Arjonilla <pacoarjonilla at yahoo dot es> ---
Using shifts and bitwise does not optimize either in GCC master, but it does
optimize in CLang.
Take this code:
#include <cstdint>
using type = std::uint32_t;
type foo(type v){
type r = (v << 24) & 0xFF000000;
r += (v << 8) & 0x00FF0000;
r += (v >> 8) & 0x0000FF00;
r += (v >> 24) & 0x000000FF;
return r;
}
CLang assembler output: ( optimize with -O2 )
mov eax, edi
bswap eax
ret
GCC master assembler output: ( optimize with -O2 )
mov eax, edi
mov edx, edi
shr eax, 24
sal edx, 24
add edx, eax
mov eax, edi
shr edi, 8
sal eax, 8
and edi, 65280
and eax, 16711680
add eax, edx
add eax, edi
ret
