Re: [PATCH][RFC][1/2] Bitfield lowering, add BIT_FIELD_EXPR

[Richard Henderson <rth@redhat.com>]

On 06/16/2011 12:14 PM, Richard Guenther wrote:
> On Thu, Jun 16, 2011 at 7:24 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>>> I think this would be clearer with a name like DEPOSIT_EXPR,
>>> similar to the ia64 deposit instruction.
>>
>> ia64's demise wasn't entirely undeserved then.  IMO the descriptive power of
>> DEPOSIT_EXPR is almost null.  BIT_FIELD_MODIFY_EXPR or something like this.
> 
> It's more like BIT_FIELD_COMPOSE_EXPR which is why I chose BIT_FIELD_EXPR,
> similar to how we have COMPLEX_EXPR which composes two scalar values.
> I don't mind changing the name though, but maybe to BIT_FIELD_COMPOSE_EXPR
> then?

That'd be fine.

> The expansion code is ad-hoc, I'm not too familiar with what utilities
> we have to do a better job here.  I'll have a look at store_bit_field
> (though that sounds memory-esque).

It probably was, originally.  But it's got paths through there to handle
writing into a register destination, which will wind up in in the 
various insv and strict_low_part patterns that the md file supports.


r~