[LLVMdev] What cause holes in a LiveInterval?

[Chris Lattner]

On Thu, 15 Dec 2005, Tzu-Chien Chiu wrote:
> LiveInterval.cpp.
>
> // that v is live at i'. In this implementation intervals can have holes,
> // i.e. an interval might look like [1,20), [50,65), [1000,1001).  Each
> // individual range is represented as an instance of LiveRange, and the whole
> // interval is represented as an instance of LiveInterval.
>
> What cause these holes?

One example is control flow.  Consider code like this:

bb1:
   X = ...
   br bb3

bb2:
   return

bb3:
   use (X)
   br bb2

X is live in BB1 and BB3, but not BB2.

-Chris

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