[Bug target/102154] [12 Regression] ICE in extract_insn, at recog.c:2769 since r12-3277-gd2874d905647a1d146dafa60199d440e837adc4d

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102154
--- Comment #7 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to Hongtao.liu from comment #6)
> Reproduced with a simple testcase
> 
> 
> float
> foo (long a)
> {
>   union{long a;
>     float b[2];}c;
>   c.a = a;
>   return c.b[1];
> }

(subreg:SF (reg:DI) 4) is genrated by extract_bit_field_as_subreg, x86 doesn't
have this error because if failed condition lowpart_bit_field_p while ppc64
passed.

the difference here is x86 is not BYTES_BIG_ENDIAN but ppc64.

static bool
lowpart_bit_field_p (poly_uint64 bitnum, poly_uint64 bitsize,
                     machine_mode struct_mode)
{
  poly_uint64 regsize = REGMODE_NATURAL_SIZE (struct_mode);
  if (BYTES_BIG_ENDIAN)
    return (multiple_p (bitnum, BITS_PER_UNIT)
            && (known_eq (bitnum + bitsize, GET_MODE_BITSIZE (struct_mode))
                || multiple_p (bitnum + bitsize,
                               regsize * BITS_PER_UNIT)));
  else
    return multiple_p (bitnum, regsize * BITS_PER_UNIT);
}