[llvm] [LoopVectorize] Add an option to test potential issues with VPlan (PR #121154)

[Danila Malyutin via llvm-commits]

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@@ -3448,8 +3453,9 @@ bool LoopVectorizationCostModel::isPredicatedInst(Instruction *I) const {
   // If predication is not needed, avoid it.
   // TODO: We can use the loop-preheader as context point here and get
   // context sensitive reasoning for isSafeToSpeculativelyExecute.
+  Instruction *CtxI = CheckSpeculatabilityAtUse ? I->getNextNode() : nullptr;
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danilaml wrote:

It is easier to do in `isSafeToSpeculativelyExecute` but then it'd mean having a LoopVectorize-only testing option in it which doesn't sound like a good idea. Or did you have something else in mind? Basically, what I need to achieve to be able to test the codegen is to consider certain loads to be `isSafeToSpeculativelyExecute == true`.

https://github.com/llvm/llvm-project/pull/121154