[Bug target/106404] New: [13 Regression] ICE: in extract_insn, at recog.cc:2791 (unrecognizable insn) with -O2 -fno-dce --param=max-cse-insns=1

[zsojka at seznam dot cz via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106404

            Bug ID: 106404
           Summary: [13 Regression] ICE: in extract_insn, at recog.cc:2791
                    (unrecognizable insn) with -O2 -fno-dce
                    --param=max-cse-insns=1
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: 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: x86_64-pc-linux-gnu

Created attachment 53334
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53334&action=edit
reduced testcase

Compiler output:
$ x86_64-pc-linux-gnu-gcc -O2 -fno-dce --param=max-cse-insns=1 testcase.c 
testcase.c: In function 'foo':
testcase.c:15:1: error: unrecognizable insn:
   15 | }
      | ^
(insn 214 133 139 4 (set (reg:V1TI 238)
        (reg:TI 193)) "testcase.c":13:5 -1
     (expr_list:REG_UNUSED (reg:V1TI 238)
        (nil)))
during RTL pass: subreg3
testcase.c:15:1: internal compiler error: in extract_insn, at recog.cc:2791
0x7782b8 _fatal_insn(char const*, rtx_def const*, char const*, int, char
const*)
        /repo/gcc-trunk/gcc/rtl-error.cc:108
0x77833b _fatal_insn_not_found(rtx_def const*, char const*, int, char const*)
        /repo/gcc-trunk/gcc/rtl-error.cc:116
0x766bed extract_insn(rtx_insn*)
        /repo/gcc-trunk/gcc/recog.cc:2791
0x2494c77 decompose_multiword_subregs
        /repo/gcc-trunk/gcc/lower-subreg.cc:1555
0x2495d9d execute
        /repo/gcc-trunk/gcc/lower-subreg.cc:1820
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
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-r13-1791-20220722100642-g1cc0e9a46e7-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/13.0.0/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 --with-cloog --with-ppl --with-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-r13-1791-20220722100642-g1cc0e9a46e7-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 13.0.0 20220722 (experimental) (GCC)