https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102143
--- Comment #5 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Uroš Bizjak from comment #3)
> gcc has also some problems in this area. With -mregparm=3, one would expect
> arguments obeying integer ABI to be passed in registers, but regparm flag
> has no effect and the same code is produced:
>
> foo:
> movd 4(%esp), %xmm0
> movd 8(%esp), %xmm1
> paddw %xmm1, %xmm0
> movd %xmm0, %eax
> ret
(sorry, sent the message too fast)
However, with -mno-sse -mregparm=3, regparm does have effect and produces:
foo:
leal (%eax,%edx), %ecx
sarl $16, %eax
sarl $16, %edx
addl %eax, %edx
movzwl %cx, %eax
sall $16, %edx
orl %edx, %eax
ret
vs -mno-sse -mregparm=0:
foo:
movl 4(%esp), %edx
movl 8(%esp), %ecx
leal (%edx,%ecx), %eax
sarl $16, %edx
sarl $16, %ecx
addl %ecx, %edx
movzwl %ax, %eax
sall $16, %edx
orl %edx, %eax
ret
