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Re: 0003-Improve-VBEout-computation.patch

On 06/16/2010 07:32 PM, Maxim Kuvyrkov wrote: 
On 6/16/10 9:27 PM, Paolo Bonzini wrote:
...

Regarding (2), I think it's fine. Still wondering about one thing
though: if an expression is available at the end of BB and computed in
BB, it is fully redundant and it should be PRE's task to remove it,
right? Maybe you're hitting the problem that our RTL PRE is not
cascading?


PRE often increases code size, so we run it when optimizing for speed.
When optimizing for size hoist is run in place of PRE. Does this answer
your question?

Yes. It looks like a valuable addition indeed.

Can you please add a comment saying "this allows the hoisting pass to also perform elimination of fully redundant expressions"?

Thanks!

Paolo

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