[llvm] [VPlan] Remove CanonicalIV when dissolving loop regions (NFC). (PR #142372)

[Luke Lau via llvm-commits]

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@@ -883,6 +883,16 @@ void VPRegionBlock::print(raw_ostream &O, const Twine &Indent,
 
 void VPRegionBlock::dissolveToCFGLoop() {
   auto *Header = cast<VPBasicBlock>(getEntry());
+  if (auto *CanIV = dyn_cast<VPCanonicalIVPHIRecipe>(&Header->front())) {
+    assert(this == getPlan()->getVectorLoopRegion() &&
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lukel97 wrote:

Just an idea, alternatively it could also be replaced in `VPlanTransforms::dissolveLoopRegions` where you could get it directly from `getCanonicalIV()`?

https://github.com/llvm/llvm-project/pull/142372