[LLVMdev] Spill Interval Generation Question

[Evan Cheng]

On Oct 5, 2007, at 5:52 PM, David Greene wrote:

>
> In LiveIntervalAnalysis::addIntervalsForSpills, we have this:
>
>           if (HasUse) {
>             LiveRange LR(getLoadIndex(index), getUseIndex(index),
>                          nI.getNextValue(~0U, 0, VNInfoAllocator));
>             DOUT << " +" << LR;
>             nI.addRange(LR);
>           }
>
> Should this actually extend from the load index to the def index since
> value intervals are exclusive at end?  Otherwise, the interval for  
> the spill
> doesn't include the use of the reloaded register, which doesn't  
> make sense to
> me.

You are probably right. Let me do some testing and fix it if that's  
the case.

>
> I think this probably went unnoticed because nothing happens with  
> intervals
> after spill code generation in the current codebase.

Yep. this will only trip over an iterative coalescer.

Evan

>
>                                               -Dave
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