CSE optimization question

[Daniel Berlin]

On Thu, 10 Jan 2002, Richard Kenner wrote:

>     Long term all the CSE path following cap should be zapped.  It's horrible
>     code with dreadful compile-time performance characteristics.  We can get
>     the same optimizations (in fact more optimizations) by doing value
>     numbering on expressions as we convert into SSA -- the cost for doing this
>     during the translation into SSA is unmeasurable.
> 
> I asked this before, but why isn't GCSE making that obsolete now? It isn't,
> but I don't understand *why* it isn't.
> 
IIRC, the main reason was that CSE eliminates dead stores. GCSE.

The actual *CSE* portion of CSE is made obsolete by our GCSE.
I did analysis to that showed this somewhere, i can try to dig it up if 
you like.

--Dan