[Bug tree-optimization/66185] New: ICE on valid code at -O3 on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66185

            Bug ID: 66185
           Summary: ICE on valid code at -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

The following code causes an ICE when compiled with the current gcc trunk at
-O3 on x86_64-linux-gnu in both 32-bit and 64-bit modes. 

It is a regression from 5.1.x. 


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20150517 (experimental) [trunk revision 223265] (GCC) 
$ 
$ gcc-trunk -O2 small.c; ./a.out
$ gcc-5.1 -O3 small.c; ./a.out
$ 
$ gcc-trunk -O3 small.c
small.c: In function ‘main’:
small.c:5:1: internal compiler error: Segmentation fault
 main ()
  ^
0xacd85f crash_signal
        ../../gcc-trunk/gcc/toplev.c:380
0xd066c8 vec<gimple_statement_base*, va_heap, vl_embed>::operator[](unsigned
int)
        ../../gcc-trunk/gcc/vec.h:736
0xd066c8 vec<gimple_statement_base*, va_heap, vl_ptr>::operator[](unsigned int)
        ../../gcc-trunk/gcc/vec.h:1202
0xd066c8 vect_analyze_slp_instance
        ../../gcc-trunk/gcc/tree-vect-slp.c:1805
0xd07606 vect_analyze_slp(_loop_vec_info*, _bb_vec_info*, unsigned int)
        ../../gcc-trunk/gcc/tree-vect-slp.c:1897
0xd07ad6 vect_slp_analyze_bb_1
        ../../gcc-trunk/gcc/tree-vect-slp.c:2431
0xd07ad6 vect_slp_analyze_bb(basic_block_def*)
        ../../gcc-trunk/gcc/tree-vect-slp.c:2561
0xd09e42 execute
        ../../gcc-trunk/gcc/tree-vectorizer.c:662
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.
$ 


------------------------------------


unsigned int a;
int b[5], c;

int
main ()
{
  for (c = 0; c < 4; c++)
    b[c] = b[c+1] > ((b[0] > 0) > a);

  return 0;
}