[Bug c++/26650] New: unaligned (SSE) stack access, smashing

["tbptbp at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

This bug is transient and sensible to code/structures re-arrangements and how
things get inlined. In the included testcases it shows up as unaligned stack
load/store but atm in the current app, i also have values being smashed on the
stack and no segfaults.

Shows up with g++ 4.1.0 and 4.2-20060225 on x86 (cygwin) and x86-64 (linux),
and in fact all 4.2.x i have tried.

With this script...
#!/usr/bin/perl
while(<>) {
        chomp;
        next if !/movaps/;
        next if !/esp/;
        next if !/(0x\w+)/;
        next if substr($1, -1, 1) eq '0';
        print "$_\n";
}

... and g++4.1.0 on cygwin...
/usr/local/gcc-4.1.0/bin/g++ -march=k8 -mfpmath=sse -msse3 -O2
-fomit-frame-pointer bogus1.ii -c -o tt1.o && objdump.exe -d --no-show-raw-insn
tt1.o |./check_alignment.pl
    1664:       movaps %xmm0,0x7c8(%esp)
    2054:       movaps %xmm0,0x318(%esp)
    28cd:       movaps %xmm0,0x1f8(%esp)
    4579:       movaps %xmm0,0x338(%esp)
    513d:       movaps %xmm0,0x328(%esp)

/usr/local/gcc-4.1.0/bin/g++ -march=k8 -mfpmath=sse -msse3 -fomit-frame-pointer
-Os bogus2.ii -c -o tt2.o && objdump.exe -d --no-show-raw-insn tt2.o
|./check_alignment.pl
     274:       movaps %xmm5,0x74(%esp)
     281:       movaps %xmm1,0x64(%esp)
     2ac:       movaps %xmm4,0x84(%esp)
     2b8:       movaps %xmm4,0x84(%esp)
     2cf:       movaps %xmm5,0x54(%esp)
     2d8:       movaps %xmm5,0x54(%esp)
     2e9:       movaps %xmm0,0x44(%esp)
     2f1:       movaps %xmm0,0x44(%esp)
     3a3:       movaps %xmm3,0x34(%esp)
     3a8:       movaps %xmm1,0x24(%esp)
     426:       movaps 0x24(%esp),%xmm7
     475:       movaps 0x34(%esp),%xmm4
     4cf:       movaps 0x64(%esp),%xmm0
     851:       movaps %xmm0,0x18(%esp)
     859:       movaps 0x18(%esp),%xmm2
     865:       movaps %xmm0,0x28(%esp)
     879:       movaps 0x18(%esp),%xmm0
     903:       movaps 0x18(%esp),%xmm0
[snipped 300 more]

Excuse those large testcases but i have no idea how to reproduce it and it only
happens in that rather large unit.


-- 
           Summary: unaligned (SSE) stack access, smashing
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tbptbp at gmail dot com
GCC target triplet: x86, x86-64


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26650