Re: Question about simplify_cond_and_lookup_avail_expr

[Jeffrey A Law <law at redhat dot com>]

On Wed, 2004-11-24 at 10:38 -0700, Jeffrey A Law wrote:
> On Wed, 2004-11-24 at 12:07 -0500, Richard Kenner wrote:
> > When looking at prev->low and prev->high, how do we know they've already
> > been computed?  Isn't the computation done lazily?
> Yes the computation is done lazily, but there will never be more
> than one unprocessed vrp element.
> 
> 1. We always call simplify_cond ... before we walk down its children
>    in the dominator tree.  If there is an element on the vrp element
>    stack, we process it.
> 
> 2. When we walk down the true arm's dominator children, we record an
>    unprocessed range for the true condition.  When we're done with the
>    true arm we pop that range off.
> 
> 3. Same as 2, but for the false arm.
> 
> If we encounter another conditional during step #2 or step #3 we 
> start the entire process again with a new conditional.  Thus
> we can never have more than 1 unprocessed element on any SSA_NAME's
> vrp element stack.
[ Replying to myself.... ]

I'll try to clarify the comments to make it clearer.

jeff