Type signature Semantic::SsaPhiNode

A phi node in the SSA form. A phi node is a kind of node in the SSA form that represents a merge point where multiple control flow paths converge and the value of a variable needs to be selected according to which control flow path was taken. For example, in the following Ruby code:

if b
  x = 0
else
  x = 1
end
puts x

A phi node for x is inserted just before the call puts x, since the value of x may come from either x = 0 or x = 1.