[Bug rtl-optimization/58997] New: ICE on valid code at -O3 on x86_64-linux-gnu (affecting gcc trunk and 4.8.2)

[su at cs dot ucdavis.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58997

            Bug ID: 58997
           Summary: ICE on valid code at -O3 on x86_64-linux-gnu
                    (affecting gcc trunk and 4.8.2)
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-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
4.8.2 at -O3 on x86_64-linux-gnu (in both 32-bit and 64-bit modes). 

It is a regression from 4.8.1. 

$ 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/4.9.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure
--enable-languages=c,c++,objc,obj-c++,fortran,lto --disable-werror
--enable-checking=release --with-gmp=/usr/local/gcc-trunk
--with-mpfr=/usr/local/gcc-trunk --with-mpc=/usr/local/gcc-trunk
--with-cloog=/usr/local/gcc-trunk --prefix=/usr/local/gcc-trunk
Thread model: posix
gcc version 4.9.0 20131105 (experimental) [trunk revision 204377] (GCC) 
$ 
$ gcc-trunk -O2 small.c; a.out
$ gcc-4.8.1 -O3 small.c; a.out
$ 
$ gcc-trunk -O3 small.c
small.c: In function ‘foo’:
small.c:18:1: internal compiler error: in simplify_subreg, at
simplify-rtx.c:5901
 }
 ^
0x82fdca simplify_subreg(machine_mode, rtx_def*, machine_mode, unsigned int)
    ../../gcc-trunk/gcc/simplify-rtx.c:5900
0x830169 simplify_gen_subreg(machine_mode, rtx_def*, machine_mode, unsigned
int)
    ../../gcc-trunk/gcc/simplify-rtx.c:6121
0x74a138 iv_subreg
    ../../gcc-trunk/gcc/loop-iv.c:439
0x74a138 iv_analyze_op
    ../../gcc-trunk/gcc/loop-iv.c:1164
0x74a257 iv_analyze_expr(rtx_def*, rtx_def*, machine_mode, rtx_iv*)
    ../../gcc-trunk/gcc/loop-iv.c:971
0x74a8c4 iv_analyze_def
    ../../gcc-trunk/gcc/loop-iv.c:1122
0x749fea iv_analyze_op
    ../../gcc-trunk/gcc/loop-iv.c:1193
0x7516ef may_unswitch_on
    ../../gcc-trunk/gcc/loop-unswitch.c:201
0x7516ef unswitch_single_loop
    ../../gcc-trunk/gcc/loop-unswitch.c:324
0x751c9c unswitch_single_loop
    ../../gcc-trunk/gcc/loop-unswitch.c:379
0x751f30 unswitch_loops()
    ../../gcc-trunk/gcc/loop-unswitch.c:148
0x742cb7 rtl_unswitch
    ../../gcc-trunk/gcc/loop-init.c:537
0x742cb7 execute
    ../../gcc-trunk/gcc/loop-init.c:567
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-4.8.2 -O3 small.c; a.out
small.c: In function ‘foo’:
small.c:18:1: internal compiler error: in simplify_subreg, at
simplify-rtx.c:5732
 }
 ^
0x7bf858 simplify_subreg(machine_mode, rtx_def*, machine_mode, unsigned int)
    ../../gcc-4.8.2/gcc/simplify-rtx.c:5731
0x7c5c18 simplify_gen_subreg(machine_mode, rtx_def*, machine_mode, unsigned
int)
    ../../gcc-4.8.2/gcc/simplify-rtx.c:5952
0x6f6438 iv_subreg
    ../../gcc-4.8.2/gcc/loop-iv.c:428
0x6f6438 iv_analyze_op
    ../../gcc-4.8.2/gcc/loop-iv.c:1154
0x6f5a2a iv_analyze_expr(rtx_def*, rtx_def*, machine_mode, rtx_iv*)
    ../../gcc-4.8.2/gcc/loop-iv.c:961
0x6f6094 iv_analyze_def
    ../../gcc-4.8.2/gcc/loop-iv.c:1112
0x6f62ea iv_analyze_op
    ../../gcc-4.8.2/gcc/loop-iv.c:1183
0x6fce35 may_unswitch_on
    ../../gcc-4.8.2/gcc/loop-unswitch.c:201
0x6fce35 unswitch_single_loop
    ../../gcc-4.8.2/gcc/loop-unswitch.c:324
0x6fd3f4 unswitch_single_loop
    ../../gcc-4.8.2/gcc/loop-unswitch.c:379
0x6fd628 unswitch_loops()
    ../../gcc-4.8.2/gcc/loop-unswitch.c:148
0x6f00a7 rtl_unswitch
    ../../gcc-4.8.2/gcc/loop-init.c:453
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, e;
short d;
char h;

int
foo ()
{
  for (; b;)
    {
      d = a ? c : 1 % a;
      c = d;
      h = d;
      if (!h) 
    for (; e;)
      ;
    }
  return 0;
}

int
main ()
{
  foo ();
  return 0;
}