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Re: [PATCH] Prefer mempcpy to memcpy on x86_64 target (PR middle-end/81657).
On Thu, Mar 29, 2018 at 01:28:13PM +0200, Martin Liška wrote:
> On 03/28/2018 06:36 PM, Jakub Jelinek wrote:
> > On Wed, Mar 28, 2018 at 06:30:21PM +0200, Martin Liška wrote:
> > > --- a/gcc/config/linux.c
> > > +++ b/gcc/config/linux.c
> > > @@ -37,3 +37,24 @@ linux_libc_has_function (enum function_class fn_class)
> > > return false;
> > > }
> > > +
> > > +/* This hook determines whether a function from libc has a fast implementation
> > > + FN is present at the runtime. We override it for i386 and glibc C library
> > > + as this combination provides fast implementation of mempcpy function. */
> > > +
> > > +enum libc_speed
> > > +ix86_linux_libc_func_speed (int fn)
> >
> > Putting a ix86_ function into config/linux.c used by most linux targets is
> > weird. Either we multiple linux targets with mempcpy fast, then name it
> > somehow cpu neutral and let all those CPUs pick it up in config/*/linux.h.
> > And yes, we do care about i?86-linux. Or it is for x86 only, and then
> > it shouldn't be in config/linux.c, but either e.g. static inline in
> > config/i386/linux.h, or we need config/i386/linux.c if we don't have it
> > already.
>
> I'm fine with putting the implementation into gcc/config/i386/linux.c. Can you please
Can't you just put it into gcc/config/i386/linux-common.h as static inline,
so that it is optimized away whenever not needed?
If you really want to add a c file, it better not be called linux.c, because
linux.o for it would clash with linux.o from gcc/config/linux.c. And,
you'd need to add the whatever.o into extra_objs in gcc/config.gcc and add
rules for it into gcc/config/i386/t-linux (see linux.o in config.gcc and
config/t-linux).
> help me how to conditionally build the file?
Jakub