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[Bug c++/25199] crashing code output from -mtune=pentium4 but not -mtune=pentiumpro
- From: "jakub at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 1 Dec 2005 14:38:15 -0000
- Subject: [Bug c++/25199] crashing code output from -mtune=pentium4 but not -mtune=pentiumpro
- References: <bug-25199-8961@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #5 from jakub at gcc dot gnu dot org 2005-12-01 14:38 -------
Finding a bug in 1M of assembly is really hard without knowing where exactly
to look at. Nevertheless, I suspect:
movl 237(%edi), %esi
in _ZN14X11SalGraphics10SetXORModeEh
(whereas -mpentiumpro .s has
movb 237(%esi), %al
). I haven't verified in detail, but it looks possible the 32bit bitfield
(out of which only 14 bits are occupied) might be the last thing in the
class, so if the bitfield happened to end up at END_OF_PAGE-240 bytes
and nothing was mapped in the next page, a crash could happen.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25199