[C++0x] contiguous bitfields race implementation

[Jason Merrill]

On 07/18/2011 08:02 AM, Aldy Hernandez wrote:
> +  /* If other threads can't see this value, no need to restrict stores.  */
> +  if (ALLOW_STORE_DATA_RACES
> +      || !DECL_THREAD_VISIBLE_P (innerdecl))
> +    {
> +      *bitstart = *bitend = 0;
> +      return;
> +    }

What if get_inner_reference returns something that isn't a DECL, such as 
an INDIRECT_REF?

> +  if (fld)
> +    {
> +      /* We found the end of the bit field sequence.  Include the
> +        padding up to the next field and be done.  */
> +      *bitend = bitpos - 1;
> +    }

bitpos is the position of "field", and it seems to me we want the 
position of "fld" here.

> +  /* If unset, no restriction.  */
> +  if (!bitregion_end)
> +    maxbits = 0;
> +  else
> +    maxbits = (bitregion_end - bitregion_start) % align;

Maybe use MAX_FIXED_MODE_SIZE so you don't have to test it against 0?

> +      if (!bitregion_end)
> +       maxbits = 0;
> +      else if (1||bitpos + offset * BITS_PER_UNIT < bitregion_start)
> +       maxbits = bitregion_end - bitregion_start;
> +      else
> +       maxbits = bitregion_end - (bitpos + offset * BITS_PER_UNIT) + 1;

I assume the 1|| was there for debugging?

Surely bitpos+offset*BITS_PER_UNIT, which would be the bit position of 
the bit-field, must be within [bitregion_start,bitregion_end)?

Jason