SD virt regs question

from the SD / SelectionDAG form of a global-virt-reg, IE a CopyToReg or CopyFromReg

where the Reg is a virtual-register (not a physical-register),

I need to compute the set of all other global-virt-regs that this one is connected

to through PHI nodes

as the PHI nodes set up equivalence relations,

I should be able to use ADT/EquivalenceClasses.h

which seems to implement a generic Union-Find algorithm,

I also note that there do not seem to be any uses of EquivalenceClasses

in CodeGen, so perhaps no one has had to do this before and I will

have to start from scratch ?

thanks,

–Peter Lawrence.