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Re: GCC build failed with your patch on 2001-01-09T11:35:00Z.
- To: Geoff Keating <geoffk at redhat dot com>, rth at redhat dot com, gcc at gcc dot gnu dot org
- Subject: Re: GCC build failed with your patch on 2001-01-09T11:35:00Z.
- From: Alexandre Oliva <aoliva at redhat dot com>
- Date: 09 Jan 2001 16:22:01 -0200
- Cc: gcc-regression at gcc dot gnu dot org, grahams at redhat dot com, jsm28 at cam dot ac dot uk, mhayes at redhat dot com, neil at daikokuya dot demon dot co dot uk, osk at hem dot passagen dot se
- Organization: GCC Team, Red Hat
- References: <200101091215.EAA27623@sloth.cygnus.com><orr92clui7.fsf@guarana.lsd.ic.unicamp.br><200101091810.KAA21760@geoffk.org>
On Jan 9, 2001, Geoff Keating <geoffk@geoffk.org> wrote:
>> But it appears to me that the bug is in rs6000.h. For a start,
>> CONST_OK_FOR_LETTER_P(VALUE, 'L') assumes right-shift does
>> sign-extension; that's not necessarily true.
> You are correct here. I will make a patch.
Thanks.
>> Second, it assumes VALUE must be signed 32-bit value, but, in this
>> case, it isn't. I haven't investigated where this value comes from,
>> so I can't tell whether it is correct for it to be a positive 64-bit
>> value or if it should have been sign-extended.
> It's always wrong for VALUE to not be a signed 32-bit value here,
> because the mode is SImode.
> You'll probably find that changing the size of HOST_WIDE_INT will
> trigger many problems, of which this is only one. I'd recommend you
> fix those problems before making the change.
I can't promise to fix all problems on all 64-bit targets. I know
there are a number of 64-bit targets that already work with a 64-bit
HOST_WIDE_INT; I was surprised that ppc wasn't one of them. I'm
pretty sure the problem must be in the ppc back-end, since there are
so many other 64-bit targets that are working correctly.
Unfortunately, I don't see myself having time to pursue ppc issues at
this time. But I do think the patch is a step in the right direction,
at the very least, because it will make it easier to find other
potential bugs lurking around in the ppc back-end.
Richard, since you approved the patch that auto-detects the need for a
64-bit HOST_WIDE_INT, I'll defer the decision about reverting it or
not to you. Just let me know...
--
Alexandre Oliva Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist *Please* write to mailing lists, not to me