Re: RFD: language hooks in GIMPLE / lang_flag?

[kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)]

> I don't understand what you are exactly trying to do, but I guess you
> want to "virtualize" the lang-hooks?  The proper way to get rid of them
> is to encode the information they provide in the IL, not to encode the
> source language in the trees.

I strongly agree and was going to say so in response to the original message.

I think that having language hooks apply to GIMPLE is wrong.  I strongly
believe that the semantics of GIMPLE ought to be defined very precisely and
in a language-independent way.  With the exception of debugging information,
I think this is true for types too: we define what the semantics of types are
independent of any particular language.

For example, I've long felt that calling a lang hook to see if two types are
"compatible" is quite wrong.  That's relevant at the language
syntactic/semantic level of validing such things as parameter lists, but to
GIMPLE two types are compatible if and only if they would produce the
identical RTL.  So two integer types are compatible if they have the same
mode, precision, and bounds.  Two FIELD_DECLs are compatible if they have the
same positions, aligments, sizes, and compatible types, two record types are
compatible if they have the same sizes and alignment and all fields are
compatible.  Etc.

The issue of debugging information is very different but I don't think in
the scope of this particular discussion.