[llvm-dev] Removing a redundant unconditional branch

[Charitha Saumya via llvm-dev]

Hi,

I want to remove a redundant unconditional branch from a Function. In the
following example I want to remove br label %26 and merge them to a single
basic block.

; <label>:9:                                      ; preds = %7
  %10 = fadd float %5, %8
  %11 = fmul float %5, %8
  %12 = fadd float %10, %11
  %13 = fdiv float %5, %8
  %14 = fadd float %13, %12
  br label %15
; <label>:15:                                     ; preds = %9
  br label %26

I tried to do this as follow but ended up getting runtime error. Can
someone help?

Thanks

Charitha
for(auto it1 = F.begin(); it1 != F.end(); it1++){
    BasicBlock& bb = *it1;
    auto BI = dyn_cast<BranchInst>(bb.getTerminator());
    if(BI && BI->isUnconditional() && bb.size() == 1){

        for (BasicBlock *pred : predecessors(&bb)) {
            auto predBI = dyn_cast<BranchInst>(pred->getTerminator());
            if(predBI && predBI->isUnconditional()){
                    predBI->setSuccessor(0, bb.getSingleSuccessor());
                    BI->dropAllReferences();
                    BI->removeFromParent();
            }
        }
    }

}
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