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[Bug rtl-optimization/40838] gcc shouldn't assume that the stack is aligned
- From: "dirtyepic at gentoo dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 29 Apr 2010 22:58:35 -0000
- Subject: [Bug rtl-optimization/40838] gcc shouldn't assume that the stack is aligned
- References: <bug-40838-1600@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #75 from dirtyepic at gentoo dot org 2010-04-29 22:58 -------
if some libraries, (zlib and fontconfig i've had personal experience with, i've
also heard libgcrypt) are compiled with -ftree-vectorize (ie. -O3) on x86
systems supporting SSE2, it causes segfaults in certain packages, usually
mozilla-based or wine, when SSE2 instructions requiring 16bit alignment are
used on unaligned data. nothing is being built with -mpreferred-stack-boundary
in these cases. this is PR41156, https://bugzilla.redhat.com/489290,
https://bugs.gentoo.org/270120. i'm not convinced this is GCC's problem. it
usually gets traced back as far as something in the mozilla codebase
misaligning the stack at which point everyone seems to give up. i've yet to
see an actual testcase, though I've encountered it several times in the wild.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40838