[llvm] [NFC][LoopVectorize] Make replaceVPBBWithIRVPBB more efficient (PR #111514)

[via llvm-commits]

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@@ -1004,13 +1004,9 @@ static void replaceVPBBWithIRVPBB(VPBasicBlock *VPBB, BasicBlock *IRBB) {
     assert(!R.isPhi() && "Tried to move phi recipe to end of block");
     R.moveBefore(*IRVPBB, IRVPBB->end());
   }
-  VPBlockBase *PredVPBB = VPBB->getSinglePredecessor();
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ayalz wrote:

This assert of having a single predecessor is now lost, yet still documented. The function traverses multiple predecessors, but probably works and tested for single predecessor only, as VPBB is still expected to be free of phi recipes? Better be clear, assert and test what is supported.

https://github.com/llvm/llvm-project/pull/111514