This helper is used later during the SSA construction and is, as its name suggest, used to insert phi-nodes in the instruction stream. More exactly, the phi-node will be put at the begining of the specified BB, just after the others phi-nodes but before any other instructions, as required for their semantics (although, it's less important for sparse since each operand correspond first to a phi-source, so no phi-node directly depending on themselves in sparse). Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>