[Bug c/63770] New: ICE on valid code at all optimization levels on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63770

            Bug ID: 63770
           Summary: ICE on valid code at all optimization levels on
                    x86_64-linux-gnu
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          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 at
all the optimization levels on x86_64-linux-gnu in both 32-bit and 64-bit
modes. 

It 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/5.0.0/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 5.0.0 20141106 (experimental) [trunk revision 217200] (GCC) 

$ 
$ gcc-4.9 -O0 -c small.c
$ 
$ gcc-trunk -O0 -c small.c
gcc-trunk: internal compiler error: Segmentation fault (program cc1)
0x40bccc execute
    ../../gcc-trunk/gcc/gcc.c:2908
0x40bfb9 do_spec_1
    ../../gcc-trunk/gcc/gcc.c:4724
0x40ea2b process_brace_body
    ../../gcc-trunk/gcc/gcc.c:6007
0x40ea2b handle_braces
    ../../gcc-trunk/gcc/gcc.c:5921
0x40cb17 do_spec_1
    ../../gcc-trunk/gcc/gcc.c:5378
0x40ea2b process_brace_body
    ../../gcc-trunk/gcc/gcc.c:6007
0x40ea2b handle_braces
    ../../gcc-trunk/gcc/gcc.c:5921
0x40cb17 do_spec_1
    ../../gcc-trunk/gcc/gcc.c:5378
0x40c443 do_spec_1
    ../../gcc-trunk/gcc/gcc.c:5493
0x40ea2b process_brace_body
    ../../gcc-trunk/gcc/gcc.c:6007
0x40ea2b handle_braces
    ../../gcc-trunk/gcc/gcc.c:5921
0x40cb17 do_spec_1
    ../../gcc-trunk/gcc/gcc.c:5378
0x40ea2b process_brace_body
    ../../gcc-trunk/gcc/gcc.c:6007
0x40ea2b handle_braces
    ../../gcc-trunk/gcc/gcc.c:5921
0x40cb17 do_spec_1
    ../../gcc-trunk/gcc/gcc.c:5378
0x40ea2b process_brace_body
    ../../gcc-trunk/gcc/gcc.c:6007
0x40ea2b handle_braces
    ../../gcc-trunk/gcc/gcc.c:5921
0x40cb17 do_spec_1
    ../../gcc-trunk/gcc/gcc.c:5378
0x40ea2b process_brace_body
    ../../gcc-trunk/gcc/gcc.c:6007
0x40ea2b handle_braces
    ../../gcc-trunk/gcc/gcc.c:5921
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.
$ 


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


char a;

struct S
{
  int f0:9;
};

volatile struct S b;

int
fn1 ()
{
  return (1 & b.f0) < a;
}