[Bug rtl-optimization/66412] New: ICE on valid code at -O2 and -O3 with -g enabled in simplify_subreg, at simplify-rtx.c:5748

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66412

            Bug ID: 66412
           Summary: ICE on valid code at -O2 and -O3 with -g enabled in
                    simplify_subreg, at simplify-rtx.c:5748
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-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
-O2 and -O3 with -g enabled on x86_64-linux-gnu in both 32-bit and 64-bit
modes.

This is a regression from 4.9.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 20150603 (experimental) [trunk revision 224056] (GCC) 
$ 
$ gcc-trunk -O2 -c small.c
$ gcc-trunk -Os -g -c small.c
$ gcc-4.9.2 -O2 -g -c small.c
$ 
$ gcc-trunk -O2 -g -c small.c
small.c: In function ‘fn1’:
small.c:12:1: internal compiler error: in simplify_subreg, at
simplify-rtx.c:5743
 }
 ^
0xae6809 simplify_subreg(machine_mode, rtx_def*, machine_mode, unsigned int)
        ../../gcc-trunk/gcc/simplify-rtx.c:5742
0xae6bf9 simplify_gen_subreg(machine_mode, rtx_def*, machine_mode, unsigned
int)
        ../../gcc-trunk/gcc/simplify-rtx.c:5962
0xae9176 simplify_replace_fn_rtx(rtx_def*, rtx_def const*, rtx_def*
(*)(rtx_def*, rtx_def const*, void*), void*)
        ../../gcc-trunk/gcc/simplify-rtx.c:524
0xd9b7ef propagate_for_debug(rtx_insn*, rtx_insn*, rtx_def*, rtx_def*,
basic_block_def*)
        ../../gcc-trunk/gcc/valtrack.c:210
0x106d801 try_combine
        ../../gcc-trunk/gcc/combine.c:4399
0x1071301 combine_instructions
        ../../gcc-trunk/gcc/combine.c:1324
0x1071301 rest_of_handle_combine
        ../../gcc-trunk/gcc/combine.c:14326
0x1071301 execute
        ../../gcc-trunk/gcc/combine.c:14369
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;

void
fn1 ()
{
  short e;
  for (c = 0; c < 1; c++)
    d = 0;
  unsigned short g = ((a == 0) ^ d) % 8;
  e = g << 1;
  b = e && 1;
}