[llvm] [VPlan] Implement interleaving as VPlan-to-VPlan transform. (PR #95842)

[Florian Hahn via llvm-commits]

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@@ -1572,3 +1572,421 @@ void VPlanTransforms::dropPoisonGeneratingRecipes(
     }
   }
 }
+
+static VPValue *getInterleavedValue(
+    DenseMap<VPValue *, SmallVector<VPValue *>> &InterleavedValues, VPValue *V,
+    unsigned IC) {
+  if (IC == 0)
+    return V;
+  if (V->isLiveIn())
+    return V;
+  return InterleavedValues[V][IC - 1];
+}
+
+static void interleaveReplicateRegion(
+    VPRegionBlock *VPR, VPlan &Plan, unsigned IC,
+    DenseMap<VPValue *, SmallVector<VPValue *>> &InterleavedValues) {
+  Type *CanIVIntTy = Plan.getCanonicalIV()->getScalarType();
+  VPBlockBase *InsertPt = VPR;
+  for (unsigned I = 1; I != IC; ++I) {
+    auto *Copy = VPR->clone();
+    VPBlockUtils::insertBlockAfter(Copy, InsertPt);
+    InsertPt = Copy;
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fhahn wrote:

Done, required adding insertBlockBefore

https://github.com/llvm/llvm-project/pull/95842