[Bug rtl-optimization/83621] New: [8 Regression] ICE: in simplify_subreg, at simplify-rtx.c:6293 with -O -g

[zsojka at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83621

            Bug ID: 83621
           Summary: [8 Regression] ICE: in simplify_subreg, at
                    simplify-rtx.c:6293 with -O -g
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu

Created attachment 42979
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42979&action=edit
reduced testcase

Compiler output:
$ x86_64-pc-linux-gnu-gcc -O -g testcase.c
during RTL pass: expand
testcase.c: In function 'foo':
testcase.c:5:1: internal compiler error: in simplify_subreg, at
simplify-rtx.c:6293
 foo ()
 ^~~
0xd21c26 simplify_subreg(machine_mode, rtx_def*, machine_mode, poly_int<1u,
unsigned long>)
        /repo/gcc-trunk/gcc/simplify-rtx.c:6293
0xd228f8 simplify_gen_subreg(machine_mode, rtx_def*, machine_mode, poly_int<1u,
unsigned long>)
        /repo/gcc-trunk/gcc/simplify-rtx.c:6534
0xd22982 lowpart_subreg(machine_mode, rtx_def*, machine_mode)
        /repo/gcc-trunk/gcc/simplify-rtx.c:6557
0x84447f expand_debug_expr
        /repo/gcc-trunk/gcc/cfgexpand.c:4226
0x850d97 expand_debug_locations
        /repo/gcc-trunk/gcc/cfgexpand.c:5362
0x850d97 execute
        /repo/gcc-trunk/gcc/cfgexpand.c:6406
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-256032-checking-yes-rtl-df-extra-nobootstrap-nographite-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/8.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--disable-bootstrap --without-cloog --without-ppl --without-isl
--build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu
--target=x86_64-pc-linux-gnu --with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-256032-checking-yes-rtl-df-extra-nobootstrap-nographite-amd64
Thread model: posix
gcc version 8.0.0 20171229 (experimental) (GCC)