@Override
    public void visitPhiInsn(PhiInsn insn) {
      RegisterSpecList sources = insn.getSources();
      RegisterSpec result = insn.getResult();
      int sz = sources.size();

      for (int i = 0; i < sz; i++) {
        RegisterSpec source = sources.get(i);
        SsaBasicBlock predBlock = blocks.get(insn.predBlockIndexForSourcesIndex(i));

        predBlock.addMoveToEnd(result, source);
      }
    }
Helper for {@link #removePhiFunctions}: PhiSuccessorUpdater for adding move instructions to
predecessors based on phi insns.
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/back/SsaToRop.java