Comment 4 for bug 1227789

Backtrace generated with gcc version 4.9.2 20140813 (prerelease)

# LANG=C gcc/cc1 -O2 -floop-parallelize-all -ffast-math /mnt/doc/cvt.i
 vprintf getchar fgetc_unlocked getc_unlocked getchar_unlocked putchar fputc_unlocked putc_unlocked putchar_unlocked feof_unlocked ferror_unlocked __signbitf __signbit __signbitl lgamma lgammaf lgammal gamma gammaf gammal tgamma tgammaf tgammal __bswap_32 __bswap_64 atoi atol atoll gnu_dev_major gnu_dev_minor gnu_dev_makedev bsearch atof mymalloc Pobsopen Pobsclose Pobspath Pobsbarriers addpt Bezier append_bezier
Analyzing compilation unit
Performing interprocedural optimizations
 <*free_lang_data> <visibility> <early_local_cleanups> <*free_inline_summary> <whole-program> <profile_estimate> <devirt> <cp> <inline> <pure-const> <static-var>Assembling functions:
 Pobsopen
cvt.c: In function 'Pobsopen':
cvt.c:62:12: internal compiler error: Segmentation fault
0xb2a43e crash_signal
        ../../gcc-4.9-20140813/gcc/toplev.c:337
0x7f12fad2098f ???
        /usr/src/glibc/glibc-2.19/signal/../sysdeps/unix/sysv/linux/x86_64/sigaction.c:0
0x1201529 subtract_commutative_associative_deps
        ../../gcc-4.9-20140813/gcc/graphite-dependences.c:430
0x1201927 compute_deps(scop*, vec<poly_bb*, va_heap, vl_ptr>, isl_union_map**, isl_union_map**, isl_union_map**, isl_union_map**, isl_union_map**, isl_union_map**, isl_union_map**, isl_union_map**, isl_union_map**, isl_union_map**, isl_union_map**, isl_union_map**)
        ../../gcc-4.9-20140813/gcc/graphite-dependences.c:502
0x1201b99 loop_level_carries_dependences
        ../../gcc-4.9-20140813/gcc/graphite-dependences.c:566
0x1201d07 loop_is_parallel_p(loop*, hash_table<bb_pbb_hasher, xcallocator>, int)
        ../../gcc-4.9-20140813/gcc/graphite-dependences.c:598
0x11fe45d translate_clast_for_loop
        ../../gcc-4.9-20140813/gcc/graphite-clast-to-gimple.c:1200
0x11fe512 translate_clast_for
        ../../gcc-4.9-20140813/gcc/graphite-clast-to-gimple.c:1224
0x11fe792 translate_clast
        ../../gcc-4.9-20140813/gcc/graphite-clast-to-gimple.c:1307
0x11fe886 translate_clast
        ../../gcc-4.9-20140813/gcc/graphite-clast-to-gimple.c:1327
0x11ff3b6 gloog(scop*, hash_table<bb_pbb_hasher, xcallocator>)
        ../../gcc-4.9-20140813/gcc/graphite-clast-to-gimple.c:1712
0x11fb371 graphite_transform_loops()
        ../../gcc-4.9-20140813/gcc/graphite.c:304
0x11fb406 graphite_transforms
        ../../gcc-4.9-20140813/gcc/graphite.c:332
0x11fb534 execute
        ../../gcc-4.9-20140813/gcc/graphite.c:416