[llvm-commits] [llvm] r56310 - /llvm/trunk/lib/CodeGen/DeadMachineInstructionElim.cpp

[Evan Cheng]

On Sep 21, 2008, at 11:17 PM, Chris Lattner wrote:

>
> On Sep 21, 2008, at 11:09 PM, Evan Cheng wrote:
>
>> Local liveness hasn't been split out from livevariables. The plan is
>> for DCE to track local liveness.
>
> Ok! That would be great, considering it is already doing a backward
> scan.  Would the register scavenger regtracker help with this?

That also works top down. If we really want accurate local liveness  
(and want to set kill / def markers, perhaps we can reuse  
RALocal::ComputeLocalLiveness().

Previously we thought this won't be necessary. But perhaps it's a good  
idea. If we move RALocal::ComputeLocalLiveness out to a analysis pass,  
then DCE can use and update it and that eliminate the need for local  
register allocator to run it.

Ultimately we want to split LiveVariables into local physical register  
liveness and global virtual register liveness. But this is a good step.

Evan

>
>
> -Chris
>
>>
>>
>> Evan
>>
>> On Sep 21, 2008, at 8:27 PM, Chris Lattner wrote:
>>
>>>
>>> On Sep 21, 2008, at 7:42 PM, Evan Cheng wrote:
>>>
>>>> This happens before livevariables. Remember we don't run LV at -O0.
>>>
>>> Not even local liveness?  That would be enough to handle physregs.
>>>
>>> -Chris
>>>
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