This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: Lazy construction of libcalls


On 9/4/07, Jan Hubicka <hubicka@ucw.cz> wrote:
> > Jan Hubicka <jh@suse.cz> writes:
> > >> Jan Hubicka <jh@suse.cz> writes:
> > >> > While comparing the tables produced by new and old code, I noticed that
> > >> > "ffs" for SI used to be called "ffssi3" but now it is "ffs".
> > >> > I believe it was inteded to be called ffs because of:
> > >> >   optab_handler (ffs_optab, int_mode)->libfunc = init_one_libfunc ("ffs");
> > >> > that however later get overwriten by initialization code.
> > >>
> > >> Actually, this was deliberate.  All libgccs have word and doubleword
> > >> ffs functions, but not all C libraries have "ffs".  So we wanted the
> > >> libgcc versions to take precedence over the C library fallback.  See:
> > >>
> > >>     http://gcc.gnu.org/ml/gcc-patches/2007-04/msg01165.html
> > >>
> > >> for details.
> > >
> > > OK, so the initialization of libgcc always overwrite the ffs
> > > initialization, so simply removing the line above would work?
> >
> > Not for 64-bit targets with a 32-bit int, since __builtin_ffs() takes
> > an int argument.  We could of course add an SImode libgcc function for
> > those targets, but the patch above was just supposed to make better
> > use of what we already had.
>
> Thanks for explanation - I've now added a guard
> if (INT_TYPE_SIZE < BITS_PER_WORD)
> into my local copy that should do what described again. I am re-testing now,
> OK with that change?

Ok.

Thanks,
Richard.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]