[Bug c/95210] New: internal compiler error: in prepare_copy_insn, at gcse.c:1988

["zhongyunde at tom dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95210

            Bug ID: 95210
           Summary: internal compiler error: in prepare_copy_insn, at
                    gcse.c:1988
           Product: gcc
           Version: 9.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhongyunde at tom dot com
  Target Milestone: ---

rtx_insn *
prepare_copy_insn (rtx reg, rtx exp)
{
  ... 
  else
    {
      rtx_insn *insn = emit_insn (gen_rtx_SET (reg, exp));

      if (insn_invalid_p (insn, false))
        gcc_unreachable ();  // here is the ICE ...
    }

  pat = get_insns ();
  end_sequence ();  

  return pat;
}

As the function can_assign_to_reg_without_clobbers_p, we try to check an
temporary insn with regno 'FIRST_PSEUDO_REGISTER * 2'. So in some corner case,
such as a pattern with inout operand, the regno 'FIRST_PSEUDO_REGISTER * 2' is
just equal to the the regno in the REG_EQUAL （FIRST_PSEUDO_REGISTER = 117）,
then the temporary insn is valid, but it come fail when alloc another regno for
it, here is this issue.

(set (reg/v:V8HF16 236 )
  (unspec: V8HF18 [ (reg: V8HF18 150)
                    (reg: V8HF18 236)] UNSPEC_MOVTVFM）) 
   (expr_list:REG_EQUAL (unspec: V8HF18 [ (reg: V8HF18 150)
                                          (reg: V8HF18 234)] UNSPEC_MOVTVFM ))

bool
can_assign_to_reg_without_clobbers_p (rtx x, machine_mode mode)
{
  .... 

  /* Otherwise, check if we can make a valid insn from it.  First initialize
     our test insn if we haven't already.  */
  if (test_insn == 0)
    {
      test_insn
        = make_insn_raw (gen_rtx_SET (gen_rtx_REG (word_mode,
                                                   FIRST_PSEUDO_REGISTER * 2),
                                      const0_rtx));
      SET_NEXT_INSN (test_insn) = SET_PREV_INSN (test_insn) = 0;
      INSN_LOCATION (test_insn) = UNKNOWN_LOCATION;
    }

  /* Now make an insn like the one we would make when GCSE'ing and see if
     valid.  */
  PUT_MODE (SET_DEST (PATTERN (test_insn)), mode);
  SET_SRC (PATTERN (test_insn)) = x;

  icode = recog (PATTERN (test_insn), test_insn, &num_clobbers);