[PATCH] D48202: Generalize MergeBlockIntoPredecessor. Replace uses of MergeBasicBlockIntoOnlyPred.

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

You may need to update Transforms/LoopSimplifyCFG/scev.ll now too (which is hopefully simple). Otherwise this looks sensible to me.



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Comment at: lib/Transforms/Utils/BasicBlockUtils.cpp:146
   // Can't merge if there are multiple successors.
   if (!OnlySucc) return false;
 
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asbirlea wrote:
> dmgreen wrote:
> > This and the previous block is just (PredBB->getUniqueSuccessor() == BB)?
> This method is expected to also merge blocks when there are multiple edges from PredBB to BB.
> Example: `test/Transforms/SimplifyCFG/2003-08-17-FoldSwitch.ll: test3`
> 
> ```
> Start:          ; preds = %0
>   switch i32 3, label %TheDest [
>   i32 0, label %TheDest
>   i32 1, label %TheDest
>   i32 2, label %TheDest
>   i32 5, label %TheDest
>   ]
> TheDest:
>   ret i32 1234
> ```
I believe this is what getUniqueSuccessor does (as opposed to getSingleSuccessor). You are not making things any worse by leaving it as it is though.


Repository:
  rL LLVM

https://reviews.llvm.org/D48202