Phi-predication for light-weight if-conversion

Predicated execution can eliminate hard to predict branches and help to enable instruction level parallelism. Many current predication variants exist where the result update is conditional based upon the outcome of the guarding predicate. However, conditional writing of a register creates a naming problem for an out-of-order processor, and can stall the issuing of instructions. This problem arises from potential multiple predicated definitions reaching a use, which is unresolved until the prior predicate values are computed.