[LLVMdev] What is "strong phi elimination"

Seung Jae Lee lee225 at uiuc.edu
Mon Mar 24 22:25:49 PDT 2008

Do you mean that "normal" SSA phi elimination algorithm is DemotePHI()?


---- Original message ----
>Date: Mon, 24 Mar 2008 21:43:06 -0700
>From: Chris Lattner <sabre at nondot.org>  
>Subject: Re: [LLVMdev] What is "strong phi elimination"  
>To: LLVM Developers Mailing List <llvmdev at cs.uiuc.edu>
>Cc: Christopher Lamb <christopher.lamb at gmail.com>
>On Mar 24, 2008, at 9:22 PM, Owen Anderson wrote:
>> Ask an ye shall receive.  From the .cpp file:
>> Basically, it's PHI elimination with built-in coallescing.
>You mean "coalescing" (tips hat to Gabor :).
>Another way to look at it is that it is the "normal" SSA phi  
>elimination algorithm, which is normally implemented in terms of an  
>interference graph, without the IG.  Not using an IG saves having to  
>build an awful N^2 data structure, which is possible through clever  
>use of SSA properties.
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