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Re: SIMPLE: A language-independent tree IR
- From: Diego Novillo <dnovillo at redhat dot com>
- To: Joe Buck <jbuck at synopsys dot COM>
- Cc: geoffk at redhat dot com, dalej at apple dot com, pkoning at equallogic dot com, toon at moene dot indiv dot nluug dot nl, gcc at gcc dot gnu dot org
- Date: Thu, 3 Jan 2002 15:59:19 -0500
- Subject: Re: SIMPLE: A language-independent tree IR
- Organization: Red Hat Canada
- References: <200201032041.MAA16057@atrus.synopsys.com> <200201032044.MAA16353@atrus.synopsys.com>
On Thu, 03 Jan 2002, Joe Buck wrote:
> I wrote:
> > Since we have the as-if rule, that's not quite the answer; we can only
> > say that the visible side effects (accesses to volatile variables,
> > calls to other functions that may have side effects) cannot be
> > interleaved. If f, g, and h are inlined, we could have considerable
> > freedom to do reordering despite the C99 rules.
>
> I don't bring this up just to nitpick. If we're going to have a common
> low-level tree representation, we need some way to represent which
> reorderings are permitted and which aren't, in a language-independent way.
>
Agreed. We could wrap partial orders in a SEQUENCE list and have
non-associative operands. Individual front-ends would be
responsible for emitting these nodes based on language rules.
Much like they do today when emitting RTL.
Diego.