https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101955
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This is also the sign extend for loading one bit.
That is take
struct g
{
int a:1;
int b0:1;
int b1:1;
int b2:1;
int b:1;
};
int h(struct g *a)
{
return a->a;
}
Currently on x86_64 -O2 GCC does:
movzbl (%rdi), %eax
sall $31, %eax
sarl $31, %eax
ret
While we should do (and llvm does):
movzbl (%rdi), %eax
andl $1, %eax
negl %eax
retq
This helps really on targets like avr more than any really.
