Re: [PATCH] x86-64: Replace movzx with movzbl

Re: [PATCH] x86-64: Replace movzx with movzbl

[Sunil Pandey]

On Tue, Nov 2, 2021 at 6:16 PM Fangrui Song via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> On 2021-11-02, H.J. Lu wrote:
> >On Tue, Nov 2, 2021 at 1:45 PM Fangrui Song <maskray@google.com> wrote:
> >>
> >> Clang cannot assemble movzx in the AT&T dialect mode.
> >>
> >> ../sysdeps/x86_64/strcmp.S:2232:16: error: invalid operand for instruction
> >>  movzx (%rsi), %ecx
> >>                ^~~~
> >>
> >> Change movzx to movzbl, which follows the AT&T dialect and is used
> >> elsewhere in the file.
> >> ---
> >>  sysdeps/x86_64/strcmp.S | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/sysdeps/x86_64/strcmp.S b/sysdeps/x86_64/strcmp.S
> >> index c7cbe4042a..bfe83abede 100644
> >> --- a/sysdeps/x86_64/strcmp.S
> >> +++ b/sysdeps/x86_64/strcmp.S
> >> @@ -2229,8 +2229,8 @@ LABEL(strcmp_exitz):
> >>
> >>         .p2align 4
> >>  LABEL(Byte0):
> >> -       movzx   (%rsi), %ecx
> >> -       movzx   (%rdi), %eax
> >> +       movzbl  (%rsi), %ecx
> >> +       movzbl  (%rdi), %eax
> >>
> >>  #if defined USE_AS_STRCASECMP_L || defined USE_AS_STRNCASECMP_L
> >>         leaq    _nl_C_LC_CTYPE_tolower+128*4(%rip), %rdx
> >> --
> >> 2.33.1.1089.g2158813163f-goog
> >>
> >
> >LGTM.
> >
> >Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
> >
> >Thanks.
>
> Thanks for the quick review!
>
> Just noticed that sysdeps/x86_64/multiarch/strcmp-sse42.S  has a similar
> pattern which needs fixing as well. I'll fix that, too.

I would like to backport this patch to release branches.
Any comments or objections?

--Sunil