Implementing the MachineBasicBlock class

Similar to basic blocks in the LLVM IR, a MachineBasicBlock class has a set of machine instructions in sequential order. Mostly, a MachineBasicBlock class maps to a single LLVM IR basic block. However, there can be cases where multiple MachineBasicBlocks classes map to a single LLVM IR basic block. The MachineBasicBlock class has a method, called getBasicBlock(), that returns the IR basic block to which it is mapping.

How to do it…

The following steps show how machine basic blocks are added:

1. The getBasicBlock method will return only the current basic block:

   const BasicBlock *getBasicBlock() const { return BB; }

2. The basic blocks have successor as well as predecessor basic blocks. To keep track of those, vectors are defined as follows:

   std::vector<MachineBasicBlock *> Predecessors;
   std::vector<MachineBasicBlock *> Successors;

3. An insert function should be added to insert a machine instruction into the basic block:

     MachineBasicBlock::insert(instr_iterator...