[llvm] [LV] Provide utility routine to find uncounted exit recipes (PR #152530)

[David Sherwood via llvm-commits]

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@@ -138,3 +138,103 @@ VPBasicBlock *vputils::getFirstLoopHeader(VPlan &Plan, VPDominatorTree &VPDT) {
   });
   return I == DepthFirst.end() ? nullptr : cast<VPBasicBlock>(*I);
 }
+
+std::optional<VPValue *> vputils::getRecipesForUncountedExit(
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david-arm wrote:

Is this function only ever intended to be called before we handle the uncountable exit, i.e. before we've introduced the middle split block? If it's after then the vplan in the comments below probably needs updating to reference the middle.split block.

It might be good to clarify in the comments where you expect this function to be called, as it seems to require the vplan CFG to be in a particular format. 

https://github.com/llvm/llvm-project/pull/152530