[LLVMdev] What is "strong phi elimination"

Chris Lattner sabre at nondot.org
Mon Mar 24 21:43:06 PDT 2008

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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