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Re: SIMPLE: A language-independent tree IR
On Tue, 2002-01-08 at 22:17, Fergus Henderson wrote:
> On 07-Jan-2002, Diego Novillo <dnovillo@redhat.com> wrote:
> > On Mon, 2002-01-07 at 04:45, Fergus Henderson wrote:
> > > Just to clarify:
> > >
> > > The idea of a language-independent tree IR in which all side-effects
> > > are *_STMT nodes rather than *_EXPR nodes ("SIMPLE trees") sounds fine,
> > > but I don't think language front-ends should use that tree IR;
> > > instead they should generate a different form of tree IR
> > > which allows *_EXPR nodes with side effects ("INITIAL trees")
> > > and then some language-independent pass can convert from
> > > INITIAL trees to SIMPLE trees.
> > >
> > > Is that what you all had in mind?
> >
> > Absolutely.
> >
> > Front-ends generate their own trees. A subsequent pass converts those
> > into li-trees. This pass will be very similar to the current tree->rtl
> > pass.
>
> Hmm, you say "Absolutely", but then what you write below it seems to
> differ a little from what I said ;-)
>
Indeed. My apologies. I completely mis-read what you were proposing.
> In particular you seem to be suggesting that the INITIAL trees be
> language-dependent, and that there be some language-dependent pass that
> converts them into language-independent SIMPLE trees.
>
Yes. The idea is to preserve the status quo of the existing
front-ends. Let them generate ld-trees. An additional pass will
simplify them and make them language-independent.
> But I think there
> should be a language-independent tree form at a higher level than SIMPLE
> trees; either the INITIAL trees should be language-independent (as I
> implied above), or there should be another language-independent form of
> trees that is used after the INITIAL trees but before the SIMPLE trees.
>
Now I think I understand what you're proposing. I'm not sure I can find
specific advantages of having the INITIAL trees be language-independent.
Do you have anything specific in mind?
Sorry for confusing things.
Diego.