public void insert(int at, DalvInsn insn) {
    insns.add(at, insn);
    updateInfo(insn);
  }
Inserts an instruction in the output at the given offset.

@param at {@code at >= 0;} what index to insert at
@param insn {@code non-null;} the instruction to insert
android/android_framework/dex-maker/src/main/java/com/android/dx/dex/code/OutputFinisher.java