[Bug target/94420] New: ICE error: insn does not satisfy its constraints

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94420

            Bug ID: 94420
           Summary: ICE error: insn does not satisfy its constraints
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marxin at gcc dot gnu.org
                CC: krebbel at gcc dot gnu.org, segher at gcc dot gnu.org
  Target Milestone: ---
              Host: powerpc64-linux-gnu
            Target: powerpc64-linux-gnu

It's reduced from moonjit bug:
https://github.com/moonjit/moonjit/issues/74

$ cat /tmp/moonjit.i
register long int *a __asm__("r2");
long int b;

void fn1() {
  long *p = &b;
  for (;;)
    *p++ = (long int)a;
}

$ ./xgcc -B. /tmp/moonjit.i -c
$ ./xgcc -B. /tmp/moonjit.i -c -O2
/tmp/moonjit.i: In function ‘fn1’:
/tmp/moonjit.i:8:1: error: insn does not satisfy its constraints:
    8 | }
      | ^
(insn 7 5 8 2 (set (reg/f:DI 121)
        (unspec:DI [
                (symbol_ref:DI ("*.LANCHOR0") [flags 0x182])
                (reg/f:DI 118 [ a.2_2 ])
            ] UNSPEC_TOCREL)) 731 {*tocrefdi}
     (expr_list:REG_EQUAL (symbol_ref:DI ("*.LANCHOR0") [flags 0x182])
        (nil)))
during RTL pass: combine
/tmp/moonjit.i:8:1: internal compiler error: in extract_constrain_insn_cached,
at recog.c:2207
0x10f19513 _fatal_insn(char const*, rtx_def const*, char const*, int, char
const*)
        ../../gcc/rtl-error.c:108
0x10f195a7 _fatal_insn_not_found(rtx_def const*, char const*, int, char const*)
        ../../gcc/rtl-error.c:119
0x10ea179f extract_constrain_insn_cached(rtx_insn*)
        ../../gcc/recog.c:2207
0x11b779b7 get_attr_prefixed(rtx_insn*)
        ../../gcc/config/rs6000/rs6000.md:647
0x116c09df rs6000_insn_cost
        ../../gcc/config/rs6000/rs6000.c:21141
0x10f30097 insn_cost(rtx_insn*, bool)
        ../../gcc/rtlanal.c:5440
0x11ef525b combine_instructions
        ../../gcc/combine.c:1236
0x11f2b06f rest_of_handle_combine
        ../../gcc/combine.c:15059
0x11f2b1e3 execute
        ../../gcc/combine.c:15104