asm streamer just prints it (``emitFnStart -> .fnstrart``), and the object
streamer implement the assembler logic for it.
+To make llvm use these classes, the target initialization must call
+TargetRegistry::RegisterAsmStreamer and TargetRegistry::RegisterMCObjectStreamer
+passing callbacks that allocate the corresponding target streamer and pass it
+to createAsmStreamer or to the appropriate object streamer constructor.
+
The ``MCContext`` class
-----------------------