[cfe-dev] Anemic support for processor based preprocessor defines

Chandler Carruth chandlerc at google.com
Wed Sep 28 14:25:03 PDT 2011


On Wed, Sep 28, 2011 at 2:07 PM, John McCall <rjmccall at apple.com> wrote:

> On Sep 28, 2011, at 1:40 PM, Anton Korobeynikov wrote:
> >> We can, but they were quite easy to lay out by hand. It's not clear to
> me
> >> that its worth the effort to teach tablegen about them unless we want to
> >> move all the architectures over, and expect the whole thing to grow a
> lot...
> > Well... we can just autogenerate all those switches, etc. and reduce
> > the "weight" of the source fileā€¦.
>
> On general principle, please try macro-metaprogramming before adding yet
> another tblgen mode.  If it's not worth a macro-metaprogram, it's definitely
> not worth tblgen.


I completely agree. Currently, I don't think it's worth that. If I go in to
modify a bunch of stuff again, I could look at this, but I'm not sure it
will really help much.

In particular, the switches are hard to hide. They include a lot of one-off
and quirky behavior in order to correctly model GCC's behavior on old chips.
(For example, see the k6, k6-2, and k6-3 silliness...)
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