This patch is based on a previous serialization patch that serializes null register operands (http://reviews.llvm.org/D10580).
This patch serializes machine basic block operands.
The following syntax is used for basic block operands:
The name is printed when the machine basic block has a name, i.e. when its basic block has a name. Otherwise, a number is printed, which is just an index into a list of machine basic blocks for that function.
JG_1 %bb.if.cond JG_1 %bb.2