[Bug c/71581] New: ICE on valid code on x86_64-linux-gnu with -Wuninitialized (Segmentation fault)

["chengniansun at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71581

            Bug ID: 71581
           Summary: ICE on valid code on x86_64-linux-gnu with
                    -Wuninitialized (Segmentation fault)
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chengniansun at gmail dot com
  Target Milestone: ---

This is a regression. gcc-4.9 and gcc-4.8 do not ICE. 

$: 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/7.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto
--prefix=/usr/local/gcc-trunk --disable-bootstrap
Thread model: posix
gcc version 7.0.0 20160618 (experimental) [trunk revision 237575] (GCC) 
$: 
$: gcc-trunk -c small.c -Wuninitialized
small.c: In function âfn1â:
small.c:4:1: internal compiler error: Segmentation fault
 }
 ^
0xbbb84f crash_signal
        ../../gcc-source-trunk/gcc/toplev.c:335
0xdbe07f warn_uninit
        ../../gcc-source-trunk/gcc/tree-ssa-uninit.c:140
0xdbe3fb warn_uninitialized_vars
        ../../gcc-source-trunk/gcc/tree-ssa-uninit.c:197
0xdbe730 execute_early_warn_uninitialized
        ../../gcc-source-trunk/gcc/tree-ssa-uninit.c:2449
0xdbe730 execute
        ../../gcc-source-trunk/gcc/tree-ssa-uninit.c:2484
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-trunk -c small.c 
$: 
$: cat small.c
_Complex long double fn1() {
  long double x;
  return x;
}
$: