[Bug tree-optimization/69186] New: ICE at -O3 on x86_64-linux-gnu in vect_update_misalignment_for_peel, at tree-vect-data-refs.c:889

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69186

            Bug ID: 69186
           Summary: ICE at -O3 on x86_64-linux-gnu in
                    vect_update_misalignment_for_peel, at
                    tree-vect-data-refs.c:889
           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 5.3.x.


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-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 20160107 (experimental) [trunk revision 232123] (GCC) 
$ 
$ gcc-trunk -O2 -c small.c
$ gcc-5.3 -O3 -c small.c
$ 
$ gcc-trunk -O3 -c small.c
small.c: In function ‘fn1’:
small.c:5:1: internal compiler error: in vect_update_misalignment_for_peel, at
tree-vect-data-refs.c:889
 fn1 ()
 ^~~

0x1238322 vect_update_misalignment_for_peel
        ../../gcc-trunk/gcc/tree-vect-data-refs.c:888
0x1246496 vect_enhance_data_refs_alignment(_loop_vec_info*)
        ../../gcc-trunk/gcc/tree-vect-data-refs.c:1829
0xd34afd vect_analyze_loop_2
        ../../gcc-trunk/gcc/tree-vect-loop.c:1975
0xd34afd vect_analyze_loop(loop*)
        ../../gcc-trunk/gcc/tree-vect-loop.c:2251
0xd4aba1 vectorize_loops()
        ../../gcc-trunk/gcc/tree-vectorizer.c:532
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.
$ 


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


static int a[10][2];
int b;

void
fn1 ()
{
  b = 0;
  for (; b < 6; b++)
    a[b][2] ^= 1;
}