[PATCH]: Implement must-def kill operand

Daniel Berlin dberlin@dberlin.org
Wed Oct 20 21:27:00 GMT 2004


On Oct 20, 2004, at 5:03 PM, Diego Novillo wrote:

> On Wed, 2004-10-20 at 16:55, Daniel Berlin wrote:
>
>> That will, in turn, mark the *feeders* of the phi as necessary, 
>> because
>> they will be added to the worklist, and propagate_necessity doesn't
>> know that it doesn't need to mark the feeders unless they are phi
>> nodes, thus you will miss dead code being eliminated.
>>
> Ah, good point.  Sigh.  I think I'm about to ask you to just let the
> regular renamer run and insert needed PHIs, but I agree that PHI node
> churn should be avoided.
>
> How much additional code are we talking about?
All told, including all necessary changes to DCE and comments, it's 89 
lines of code added.

> A good chunk of the
> algorithm you described already exists in DCE.  Can it be factored?
I factored what i could. :)

>
>
> Diego.
>



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