public final void mapRegisters(RegisterMapper mapper) {
    RegisterSpec oldResult = result;

    result = mapper.map(result);
    block.getParent().updateOneDefinition(this, oldResult);
    mapSourceRegisters(mapper);
  }
Map registers after register allocation.

@param mapper {@code non-null;} mapping from old to new registers
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/SsaInsn.java