[Bug target/84710] New: [8 Regression] ICE: RTL check: expected code 'reg', have 'subreg' in rhs_regno, at rtl.h:1896 with -O -fno-forward-propagate

[zsojka at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84710

            Bug ID: 84710
           Summary: [8 Regression] ICE: RTL check: expected code 'reg',
                    have 'subreg' in rhs_regno, at rtl.h:1896 with -O
                    -fno-forward-propagate
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: ice-checking, ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: aarch64-unknown-linux-gnu

Created attachment 43561
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43561&action=edit
reduced testcase

Compiler output:
$ aarch64-unknown-linux-gnu-gcc -O -fno-forward-propagate testcase.c
during RTL pass: combine
testcase.c: In function 'foo':
testcase.c:9:1: internal compiler error: RTL check: expected code 'reg', have
'subreg' in rhs_regno, at rtl.h:1896
 }
 ^
0x5b8938 rtl_check_failed_code1(rtx_def const*, rtx_code, char const*, int,
char const*)
        /repo/gcc-trunk/gcc/rtl.c:846
0x5e73c5 rhs_regno
        /repo/gcc-trunk/gcc/rtl.h:1896
0x13e0ae8 rhs_regno
        /repo/gcc-trunk/gcc/rtl.h:1447
0x13e0ae8 try_combine
        /repo/gcc-trunk/gcc/combine.c:4291
0x13e6682 combine_instructions
        /repo/gcc-trunk/gcc/combine.c:1320
0x13e6682 rest_of_handle_combine
        /repo/gcc-trunk/gcc/combine.c:14886
0x13e6682 execute
        /repo/gcc-trunk/gcc/combine.c:14931
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.

$ aarch64-unknown-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-aarch64/bin/aarch64-unknown-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-258241-checking-yes-rtl-df-extra-aarch64/bin/../libexec/gcc/aarch64-unknown-linux-gnu/8.0.1/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--with-cloog --with-ppl --with-isl
--with-sysroot=/usr/aarch64-unknown-linux-gnu --build=x86_64-pc-linux-gnu
--host=x86_64-pc-linux-gnu --target=aarch64-unknown-linux-gnu
--with-ld=/usr/bin/aarch64-unknown-linux-gnu-ld
--with-as=/usr/bin/aarch64-unknown-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-258241-checking-yes-rtl-df-extra-aarch64
Thread model: posix
gcc version 8.0.1 20180305 (experimental) (GCC) 

Tested revisions:
r258241 - ICE
r258075 - ICE
7-branch r258055 - OK