> Date: Tue, 11 Sep 2012 17:03:39 -0700
> From: Ian Lance Taylor <i...@google.com>
>
> On Tue, Sep 11, 2012 at 3:12 PM, Lawrence Crowl <cr...@googlers.com> wrote:
> > On 9/11/12, Andreas Schwab <sch...@linux-m68k.org> wrote:
> >> Mark Kettenis <mark.kette...@xs4all.nl> writes:
> >>> In file included from ../../../src/gcc/gcc/mcf.c:47:0:
> >>> ../../../src/gcc/gcc/mcf.c: In function 'void dump_fixup_edge(FILE*,
> >>> fixup_graph_type*, fixup_edge_p)':
> >>> ../../../src/gcc/gcc/system.h:288:78: error: integer overflow in
> >>> expression [-Werror=overflow]
> >>
> >> This is PR54528.
> >
> > The expression itself looks correct. I have not been able to
> > duplicate the problem on x86. I am now waiting on access to the
> > compile farm for access to a hppa system. Does anyone have more
> > specific information on the condition that generates the error?
>
> I haven't tried, but I bet you can get it to happen if you build a
> 32-bit compiler--that is, build a compiler using -m32 so that the
> compiler itself runs 32 bit code.
I don't think that helps since I don't see the problem on OpenBSD/i386
(i386-unknown-openbsd5.2) whith a strictly 32-bit compiler. As I
wrote earlier, I suspect the key factor is HOST_WIDE_INT being 32-bit,
which means 32-bit architectures that don't sey need_64bit_hwint in
config.gcc. The fact that m68k is affected as well strengthens my
suspicion. So I expect arm to show the problem as well. But people
probably haven't noticed since they cross-compile.
Anyway the "diff" below seems to fix the issue. Guess the replacement
doesn't work! Should be a big enough clue for Lawrence to come up
with a proper fix.
Index: fold-const.c
===================================================================
--- fold-const.c (revision 191150)
+++ fold-const.c (working copy)
@@ -982,13 +982,15 @@
break;
case MINUS_EXPR:
-/* FIXME(crowl) Remove this code if the replacment works.
+ /* FIXME(crowl) Remove this code if the replacment works. */
+#if 1
neg_double (op2.low, op2.high, &res.low, &res.high);
add_double (op1.low, op1.high, res.low, res.high,
&res.low, &res.high);
overflow = OVERFLOW_SUM_SIGN (res.high, op2.high, op1.high);
-*/
+#else
res = op1.add_with_sign (-op2, false, &overflow);
+#endif
break;
case MULT_EXPR:
