https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113729
--- Comment #2 from Hongtao Liu <liuhongt at gcc dot gnu.org> ---
extern unsigned char b;
int
foo (void)
{
return (unsigned char)(200 + b);
}
gcc -O2 -mapxf
foo():
subb $56, b(%rip), %al
movzbl %al, %eax
ret
And this can be optimzied to
foo():
subb $56, b(%rip), %al
ret
Note, if we want to optimize it in pass_combine, the pattern need to generate
explicit APX NDD instructions, since APX non-NDD will not clear upper bits.
