Question

For a basic block I want to change conditional jump to an unconditional jump. So if a basic block had two successors I want to remove the edge to one of the successor. I want the basic block to directly jump to one of the successor. How can I do that?

To illustrate my point, I want to change

      A
    /  \
   /    \
  B      C

to

     A
      \
       \
        C

Answer 1

I think the simplest way will be just to create a new unconditional branch instruction, then replace the old one with it. So, something like:

#include "llvm/Transforms/Utils/BasicBlockUtils.h"

BranchInst* Old = ...
BranchInst* New = BranchInst::Create(Old->getSuccessor(X));
ReplaceInstWithInst(Old, New);

Where X is 0 or 1, depending if you want the “true” branch or the “false” branch.