[Bug tree-optimization/68324] 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=68324

            Bug ID: 68324
           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 5.2.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 20151112 (experimental) [trunk revision 230270] (GCC) 
$ 
$ gcc-trunk -O2 -c small.c
$ gcc-5.2 -O3 -c small.c
$  
$ gcc-trunk -O3 -c small.c
small.c: In function ‘fn1’:
small.c:4:1: internal compiler error: Segmentation fault
 fn1 ()
 ^

0xaf782f crash_signal
        ../../gcc-trunk/gcc/toplev.c:336
0x12578a4 dr_misalignment(data_reference*)
        ../../gcc-trunk/gcc/tree-vectorizer.h:889
0x12578a4 aligned_access_p
        ../../gcc-trunk/gcc/tree-vectorizer.h:902
0x12578a4 vect_supportable_dr_alignment(data_reference*, bool)
        ../../gcc-trunk/gcc/tree-vect-data-refs.c:5863
0xd2a761 vectorizable_load
        ../../gcc-trunk/gcc/tree-vect-stmts.c:6706
0xd338d6 vect_transform_stmt(gimple*, gimple_stmt_iterator*, bool*, _slp_tree*,
_slp_instance*)
        ../../gcc-trunk/gcc/tree-vect-stmts.c:7997
0xd4b354 vect_schedule_slp_instance
        ../../gcc-trunk/gcc/tree-vect-slp.c:3468
0xd4b1a9 vect_schedule_slp_instance
        ../../gcc-trunk/gcc/tree-vect-slp.c:3349
0xd4cf46 vect_schedule_slp(vec_info*)
        ../../gcc-trunk/gcc/tree-vect-slp.c:3533
0xd505ec vect_slp_bb(basic_block_def*)
        ../../gcc-trunk/gcc/tree-vect-slp.c:2525
0xd52645 execute
        ../../gcc-trunk/gcc/tree-vectorizer.c:738
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.
$ 


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


int a[10], b, c, d;

void
fn1 ()
{
  for (; b;)
    for (d = 1; d < 5; d++)
      for (c = 0; c < 2; c++)
        a[c * 5 + d] = a[c];
}