public RegisterSpecSet mutableCopyOfStarts(int label) {
    RegisterSpecSet result = getStarts0(label);

    return (result != null) ? result.mutableCopy() : new RegisterSpecSet(regCount);
  }
Gets a mutable copy of the register set associated with the start of the block with the given
label. This returns a newly-allocated empty {@link RegisterSpecSet} of appropriate max size if
there is not yet any set associated with the block.

@param label {@code >= 0;} the block label
@return {@code non-null;} the associated register set
android/android_framework/dex-maker/src/main/java/com/android/dx/rop/code/LocalVariableInfo.java