[Bug tree-optimization/61917] New: ICE on valid code at -O3 on x86_64-linux-gnu in vectorizable_reduction, at tree-vect-loop.c:4913

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61917

            Bug ID: 61917
           Summary: ICE on valid code at -O3 on x86_64-linux-gnu in
                    vectorizable_reduction, at tree-vect-loop.c:4913
           Product: gcc
           Version: 4.10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The following code causes an ICE when compiled with the current gcc trunk and
gcc 4.9 at -O3 on x86_64-linux-gnu (in both 32-bit and 64-bit modes).

It is a regression from 4.8.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/4.10.0/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 4.10.0 20140725 (experimental) [trunk revision 213036] (GCC) 
$ 
$ gcc-trunk -O2 -c small.c
$ gcc-4.8 -O3 -c small.c
$ 
$ gcc-trunk -O3 -c small.c
small.c: In function ‘fn1’:
small.c:4:1: internal compiler error: in vectorizable_reduction, at
tree-vect-loop.c:4913
 fn1 ()
 ^
0xb8eb3c vectorizable_reduction(gimple_statement_base*, gimple_stmt_iterator*,
gimple_statement_base**, _slp_tree*)
    ../../gcc-trunk/gcc/tree-vect-loop.c:4913
0xb8144f vect_analyze_stmt(gimple_statement_base*, bool*, _slp_tree*)
    ../../gcc-trunk/gcc/tree-vect-stmts.c:7103
0xb8ccee vect_analyze_loop_operations
    ../../gcc-trunk/gcc/tree-vect-loop.c:1505
0xb8ccee vect_analyze_loop_2
    ../../gcc-trunk/gcc/tree-vect-loop.c:1766
0xb8ccee vect_analyze_loop(loop*)
    ../../gcc-trunk/gcc/tree-vect-loop.c:1864
0xba50cf vectorize_loops()
    ../../gcc-trunk/gcc/tree-vectorizer.c:432
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.
$ 
$ gcc-4.9 -O3 -c small.c
small.c: In function ‘fn1’:
small.c:4:1: internal compiler error: in vectorizable_reduction, at
tree-vect-loop.c:4907
 fn1 ()
 ^
0x9b6f35 vectorizable_reduction(gimple_statement_base*, gimple_stmt_iterator*,
gimple_statement_base**, _slp_tree*)
    ../../gcc-4.9.0/gcc/tree-vect-loop.c:4907
0x9a94e8 vect_analyze_stmt(gimple_statement_base*, bool*, _slp_tree*)
    ../../gcc-4.9.0/gcc/tree-vect-stmts.c:7103
0x9b54e6 vect_analyze_loop_operations
    ../../gcc-4.9.0/gcc/tree-vect-loop.c:1505
0x9b54e6 vect_analyze_loop_2
    ../../gcc-4.9.0/gcc/tree-vect-loop.c:1765
0x9b54e6 vect_analyze_loop(loop*)
    ../../gcc-4.9.0/gcc/tree-vect-loop.c:1863
0x9c9f3b vectorize_loops()
    ../../gcc-4.9.0/gcc/tree-vectorizer.c:430
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, b, c, d;

int
fn1 ()
{
  for (; c; c++)
    for (b = 0; b < 2; b++)
      d = a - d;
  return d; 
}