Liveness analysis of a fun is triggered as follows for Python
liveness.FunComputeLivenessInfo(fun)
This will make the following datastructure available:
bbl.live_out: Set[Reg] # set of reg live at the end of the Bbl
For C++ things are only slightly more elaborate:
FunNumberReg(fun); // create an injective mapping int <-> Reg
FunComputeLivenessInfo(fun); // compute the actual liveness information
This will make the following datastructures available:
bv = BblLiveOut(Bbl bbl) // a BitVec that can be queried like so:
bv.GetBit(RegNo(reg));
Usage
We only save the liveness information at the end of the bbl.
To use liveness information at the ins level, iterate backwards
through the ins in the bbl and update the liveness info along the way.
Liveness is primarily used to compute live ranges.