[Bug target/96849] New: [11 Regression] ICE: in extract_insn, at recog.c:2294 (error: unrecognizable insn)

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96849

            Bug ID: 96849
           Summary: [11 Regression] ICE: in extract_insn, at recog.c:2294
                    (error: unrecognizable insn)
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---
            Target: x86_64-unknown-linux-gnu-gcc

gcc-11.0.0-alpha20200823 snapshot (g:87c753ac241f25d222d46ba1ac66ceba89d6a200)
ICEs when compiling the following testcase, reduced from
gcc/testsuite/gcc.target/powerpc/p9-vec-length-epil-run-1.c, w/ -mavx512f -O1
-ftree-loop-vectorize:

double my[16];

void
lw (unsigned int dd)
{
  while (dd < 16)
    {
      my[dd] = dd;
      ++dd;
    }
}

% x86_64-unknown-linux-gnu-gcc-11.0.0 -mavx512f -O1 -ftree-loop-vectorize -c
ppoh4ko6.c
ppoh4ko6.c: In function 'lw':
ppoh4ko6.c:11:1: error: unrecognizable insn:
   11 | }
      | ^
(insn 33 32 34 5 (set (reg:QI 116)
        (lt:QI (reg:V8DF 115)
            (reg:V8DF 113))) "ppoh4ko6.c":8:14 -1
     (nil))
during RTL pass: vregs
ppoh4ko6.c:11:1: internal compiler error: in extract_insn, at recog.c:2294
0x689824 _fatal_insn(char const*, rtx_def const*, char const*, int, char
const*)
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200823/work/gcc-11-20200823/gcc/rtl-error.c:108
0x689840 _fatal_insn_not_found(rtx_def const*, char const*, int, char const*)
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200823/work/gcc-11-20200823/gcc/rtl-error.c:116
0x687d04 extract_insn(rtx_insn*)
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200823/work/gcc-11-20200823/gcc/recog.c:2294
0xa91c95 instantiate_virtual_regs_in_insn
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200823/work/gcc-11-20200823/gcc/function.c:1607
0xa91c95 instantiate_virtual_regs
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200823/work/gcc-11-20200823/gcc/function.c:1977
0xa91c95 execute
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20200823/work/gcc-11-20200823/gcc/function.c:2026