[PATCH] D43822: [CloneFunction] Support BB == PredBB in DuplicateInstructionsInSplit.

[Florian Hahn via Phabricator via llvm-commits]

fhahn added inline comments.


================
Comment at: lib/Transforms/Utils/CloneFunction.cpp:814
   // mapping and using it to remap operands in the cloned instructions.
-  for (; StopAt != &*BI; ++BI) {
+  // Stop once we see the terminator too. This covers the case where BB's
+  // terminator gets replaced and StopAt == BB's terminator.
----------------
anna wrote:
> Basically, StopAt was pointing to the old terminator of BB before it was replaced. `SplitEdge` does not update BB's terminator. So, where exactly, is the update happening for BB's terminator now?
> 
> If PredBB == BB, then BB's terminator should be updated from "br i1 <cond> BB, otherBB" to "br i1 <cond> NewBB, otherBB".
> 
The case that caused the crash was PredBB == BB and BB has an unconditional branch as a terminator. Then we split BB at the terminator, which replaces the terminator of BB (relevant line in SplitEdge https://reviews.llvm.org/diffusion/L/browse/llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp;326450$273 , BasicBlock::splitBasicBlock, which is used by SplitBlock https://reviews.llvm.org/diffusion/L/browse/llvm/trunk/lib/IR/BasicBlock.cpp;326450$372)




https://reviews.llvm.org/D43822