Re: [PATCH]: Reduce memory usage and compile time necessary for pruning

[Daniel Berlin <dberlin at dberlin dot org>]

On Mon, 2006-03-13 at 10:16 -0500, Diego Novillo wrote:
> On 03/12/06 16:29, Daniel Berlin wrote:
> 
> > Any idea what to do here?
> > 
> Not really.  Introducing another temporary might be tempting, but we're
> already temporary-happy, and these are fairly bulky objects.
> 
> With any luck, any workaround you implement will be temporary.  The
> whole tag-is-used-alone thing will not be needed with the new scheme.
> How about a bit in the virtual operand itself to indicate whether it's
> an LHS or an RHS V_MAY_DEF?

This is my inclination, but it would have to be two bits, because it
could be because of both.
In fact, in this case, it *is*, because the SMT is def'd by both the
call, *and* the store on the LHS.

We just don't add two may defs because we don't add duplicate may-defs.

I'm actually going to see how bad things are as a temporary hack if we 

1. try to determine what tags the lhs may def in this special case of
having a call store to something that may-def things.

or
2. Try to take the conservative route of marking may-defs from calls
when the lhs may generate may-defs (the problem with this is that it may
cause random changes to call statements to need used_alone
recalculation, so it may not work).

If it becomes ugly at all, i will add some bits :)