SIMPLE: A language-independent tree IR

[Diego Novillo]

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.