[llvm-commits] [llvm] r46218 - /llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp

[Evan Cheng]

Hi Owen,

I am not sure I completely understand the comment. Are you saying when  
a VReg is found to be live out of its definition block. This decides  
whether to place the copy in the definition block or in the use block?

Evan

On Jan 21, 2008, at 2:03 PM, Owen Anderson wrote:

> Author: resistor
> Date: Mon Jan 21 16:03:00 2008
> New Revision: 46218
>
> URL: http://llvm.org/viewvc/llvm-project?rev=46218&view=rev
> Log:
> Clarify a deviation from the original algorithm.
>
> Modified:
>    llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp
>
> Modified: llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp?rev=46218&r1=46217&r2=46218&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp (original)
> +++ llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp Mon Jan 21  
> 16:03:00 2008
> @@ -552,7 +552,10 @@
>       DomForestNode* child = *CI;
>
>       // If the current node is live-out of the defining block of  
> one of its
> -      // children, insert a copy for it
> +      // children, insert a copy for it.  NOTE: The paper actually  
> calls for
> +      // a more elaborate heuristic for determining whether to  
> insert copies
> +      // for the child or the parent.  In the interest of  
> simplicity, we're
> +      // just always choosing the parent.
>       if (isLiveOut(DFNode->getReg(),
>           MRI.getVRegDef(child->getReg())->getParent(), MRI, LV)) {
>         // Insert copies for parent
>
>
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