[llvm] [VPlan] Implement cloning of VPlans. (PR #73158)

[via llvm-commits]

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@@ -982,6 +994,65 @@ void VPlan::updateDominatorTree(DominatorTree *DT, BasicBlock *LoopHeaderBB,
   assert(DT->verify(DominatorTree::VerificationLevel::Fast));
 }
 
+static void remapVPValues(VPBasicBlock *OldBB, VPBasicBlock *NewBB,
+                          DenseMap<VPValue *, VPValue *> &Old2NewVPValues,
+                          bool Full = false) {
+  for (const auto &[OldR, NewR] : zip(*OldBB, *NewBB)) {
+    for (unsigned I = 0, E = NewR.getNumOperands(); I != E; ++I) {
+      VPValue *NewOp = Old2NewVPValues.lookup(OldR.getOperand(I));
+      if (!Full)
+        continue;
+      NewR.setOperand(I, NewOp);
+    }
+    for (const auto &[OldV, NewV] :
+         zip(OldR.definedValues(), NewR.definedValues()))
+      Old2NewVPValues[OldV] = NewV;
+  }
+}
+
+VPlan *VPlan::clone() {
+  DenseMap<VPBlockBase *, VPBlockBase *> Old2New;
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ayalz wrote:

nit:
```suggestion
  DenseMap<VPBlockBase *, VPBlockBase *> Old2NewBlocks;
```
for consistency.

https://github.com/llvm/llvm-project/pull/73158