[Bug target/59363] New: [4.9 Regression] r203886 miscompiles git

[octoploid at yandex dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59363

            Bug ID: 59363
           Summary: [4.9 Regression] r203886 miscompiles git
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: octoploid at yandex dot com

Starting with r203886 git gets miscompiled on my machine.
For example:

 % git blame gcc/tree-object-size.c

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x000000000051240d in xdl_emit_hunk_hdr (s1=s1@entry=1291, c1=<optimized
out>, s2=s2@entry=1291, c2=c2@entry=1, func=func@entry=0x7fffffffd2d8 "",
funclen=0, 
    ecb=ecb@entry=0x7fffffffd580) at xdiff/xutils.c:460
#2  0x0000000000512af7 in xdl_emit_diff (xe=0x7fffffffd390, xscr=<optimized
out>, ecb=0x7fffffffd580, xecfg=0x7fffffffd590) at xdiff/xemit.c:237
#3  0x0000000000510a5d in xdl_diff (mf1=mf1@entry=0x7fffffffd510,
mf2=mf2@entry=0x7fffffffd520, xpp=xpp@entry=0x7fffffffd570,
xecfg=xecfg@entry=0x7fffffffd590, 
    ecb=ecb@entry=0x7fffffffd580) at xdiff/xdiffi.c:601
#4  0x000000000050b005 in xdi_diff (mf1=<optimized out>, mf2=<optimized out>,
xpp=xpp@entry=0x7fffffffd570, xecfg=xecfg@entry=0x7fffffffd590,
xecb=xecb@entry=0x7fffffffd580)
    at xdiff-interface.c:136
#5  0x00000000004104df in diff_hunks (file_a=<optimized out>, file_b=<optimized
out>, ctxlen=ctxlen@entry=0, hunk_func=hunk_func@entry=0x411320
<blame_chunk_cb>, 
    cb_data=cb_data@entry=0x7fffffffd830) at builtin/blame.c:105
#6  0x0000000000412b54 in pass_blame_to_parent (parent=0x144a7b0,
target=0x125dcb0, sb=0x7fffffffd6e0) at builtin/blame.c:815
#7  pass_blame (opt=0, origin=0x125dcb0, sb=0x7fffffffd6e0) at
builtin/blame.c:1281
#8  assign_blame (opt=<optimized out>, sb=0x7fffffffd6e0) at
builtin/blame.c:1559
#9  cmd_blame (argc=<optimized out>, argv=<optimized out>, prefix=<optimized
out>) at builtin/blame.c:2523
#10 0x00000000004060b5 in run_builtin (argv=0x7fffffffe528, argc=2, p=0x578bd8
<commands.22612+120>) at git.c:314
#11 handle_internal_command (argc=2, argv=0x7fffffffe528) at git.c:478
#12 0x0000000000405772 in main (argc=2, av=<optimized out>) at git.c:575

This only happens when I compile git with -march=native (=amdfam10 on this
machine).

I will try to come up with a testcase tomorrow.