public void addInsnToHead(Insn insn) {
    SsaInsn newInsn = SsaInsn.makeFromRop(insn, this);
    insns.add(getCountPhiInsns(), newInsn);
    parent.onInsnAdded(newInsn);
  }
Adds an insn to the head of this basic block, just after any phi insns.

@param insn {@code non-null;} rop-form insn to add
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/SsaBasicBlock.java