void onInsnRemoved(SsaInsn insn) {
    if (useList != null) {
      removeFromUseList(insn, insn.getSources());
    }

    RegisterSpec resultReg = insn.getResult();
    if (definitionList != null && resultReg != null) {
      definitionList[resultReg.getReg()] = null;
    }
  }
Removes an instruction from use and def lists. For use during instruction removal.

@param insn {@code non-null;} insn to remove
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/SsaMethod.java