On Fri, Nov 13, 2015 at 04:53:05PM +0100, Marek Polacek wrote:
> On Fri, Nov 13, 2015 at 04:44:21PM +0100, Bernd Schmidt wrote:
> > On 11/13/2015 04:11 PM, Marek Polacek wrote:
> > >Sorry, I changed my mind. Since QUAL_UNION_TYPE is Ada-only thing and
> > >we check (RECORD_TYPE || UNION_TYPE) in a lot of places in the C FE,
> > >introducing RECORD_OR_UNION_TYPE_P everywhere would unnecessarily slow
> > >things down.
> >
> > I don't think so, the three codes are adjacent so we should be generating
> > "(unsigned)(code - RECORD_TYPE) < 3".
>
> Interesting. Yeah, if we change the RECORD_OR_UNION_TYPE_P macro to this
> form, then we don't need a separate version for the C FE.
Why? The compiler should do that already, or do you care about
-O0 builds or host compilers other than gcc that aren't able to do this?
The disadvantage of writing it manually that way is that you need to assert
somewhere that the 3 values indeed are consecutive, while
when the (host?) compiler performs this optimization, it does that only if
they are consecutive, if they are not, the code will be just less efficient.
Jakub
