[llvm] [VPlan] Make canonical IV part of the region (PR #156262)

[via llvm-commits]

================
@@ -4443,24 +4403,33 @@ class LLVM_ABI_FOR_TEST VPRegionBlock : public VPBlockBase {
   /// its entry, and its exiting block to its successor.
   void dissolveToCFGLoop();
 
-  /// Returns the canonical induction recipe of the region.
-  VPCanonicalIVPHIRecipe *getCanonicalIV() {
-    VPBasicBlock *EntryVPBB = getEntryBasicBlock();
-    if (EntryVPBB->empty()) {
-      // VPlan native path. TODO: Unify both code paths.
-      EntryVPBB = cast<VPBasicBlock>(EntryVPBB->getSingleSuccessor());
-    }
-    return cast<VPCanonicalIVPHIRecipe>(&*EntryVPBB->begin());
+  /// Get the canonical IV increment instruction. If the exiting terminator
+  /// is a BranchOnCount with an IV increment, return this increment. Otherwise,
+  /// return nullptr.
+  VPInstruction *getOrCreateCanonicalIVIncrement();
+
+  /// Return the canonical induction variable of the region, null for
+  /// replicating regions.
+  VPRegionValue *getCanonicalIV() {
+    return CanIVInfo ? CanIVInfo->getVPValue() : nullptr;
   }
-  const VPCanonicalIVPHIRecipe *getCanonicalIV() const {
-    return const_cast<VPRegionBlock *>(this)->getCanonicalIV();
+  const VPRegionValue *getCanonicalIV() const {
+    return CanIVInfo ? CanIVInfo->getVPValue() : nullptr;
   }
 
-  /// Return the type of the canonical IV for loop regions.
-  Type *getCanonicalIVType() { return getCanonicalIV()->getScalarType(); }
-  const Type *getCanonicalIVType() const {
-    return getCanonicalIV()->getScalarType();
+  /// Return the type of the canonical IV for loop regions
----------------
ayalz wrote:

```suggestion
  /// Return the type of the canonical IV for loop regions.
```

https://github.com/llvm/llvm-project/pull/156262