s.hasDef = newSparseSet(s.f.NumBlocks())
	s.placeholder = s.s.entryNewValue0(ssa.OpUnknown, types.TypeInvalid)

	// Generate phi ops for each variable.
	for n := range vartypes {
		s.insertVarPhis(n, vars[n], defs[n], vartypes[n])
	}

	// Resolve FwdRefs to the correct write or phi.
	s.resolveFwdRefs()

	// Erase variable numbers stored in AuxInt fields of phi ops. They are no longer needed.