Re: [PATCH v2] break gdb build on 32-bit host with ADI support

[Pedro Alves <palves@redhat.com>]

$subject should be "unbreak", I hope.  :-)

On 08/25/2017 02:33 AM, Weimin Pan wrote:

> @@ -240,7 +242,7 @@ adi_normalize_address (CORE_ADDR addr)
>    adi_stat_t ast = get_adi_info (ptid_get_pid (inferior_ptid));
>  
>    if (ast.nbits)
> -    return ((CORE_ADDR)(((long)addr << ast.nbits) >> ast.nbits));
> +    return (addr & ((1 << ast.nbits) - 1)) ^ (addr & (-1 >> ast.nbits));

How did you test this?  Doesn't look right to me.
Also, "-1 >>" is still an implementation-defined signed
right shift.

I _think_ this is what you want:

  /* Clear upper bits.  */
  addr &= ((uint64_t) -1) >> ast.nbits;

  /* Sign extend.  */
  CORE_ADDR signbit = (uint64_t) 1 << (64 - ast.nbits - 1);
  return (addr ^ signbit) - signbit;

I.e., with ast.nbits == 4:

 before: ffffffffffffffff
 after:  ffffffffffffffff

 before: f7ffffffffffffff
 after:  07ffffffffffffff

Thanks,
Pedro Alves