[llvm] [VPlan] Add transformation to narrow interleave groups. (PR #106441)

[Alexey Bataev via llvm-commits]

================
@@ -1921,3 +1924,123 @@ void VPlanTransforms::handleUncountableEarlyExit(
   Builder.createNaryOp(VPInstruction::BranchOnCond, AnyExitTaken);
   LatchExitingBranch->eraseFromParent();
 }
+
+static bool supportedLoad(VPWidenRecipe *R0, VPValue *V, unsigned Idx) {
+  if (auto *W = dyn_cast_or_null<VPWidenLoadRecipe>(V->getDefiningRecipe()))
+    return !W->getMask() && (R0->getOperand(0) == V || R0->getOperand(1) == V);
+
+  if (auto *IR = dyn_cast_or_null<VPInterleaveRecipe>(V->getDefiningRecipe()))
+    return IR->getInterleaveGroup()->getFactor() ==
+               IR->getInterleaveGroup()->getNumMembers() &&
+           IR->getVPValue(Idx) == V;
+  return false;
+}
+
+/// Returns true if \p IR is a full interleave group with factor and number of
+/// members both equal to \p VF.
+static bool isConsecutiveInterleaveGroup(VPInterleaveRecipe *IR,
+                                         ElementCount VF) {
+  if (!IR)
+    return false;
+  auto IG = IR->getInterleaveGroup();
+  return IG->getFactor() == IG->getNumMembers() &&
+         IG->getNumMembers() == VF.getFixedValue();
+}
+
+void VPlanTransforms::narrowInterleaveGroups(VPlan &Plan, ElementCount VF) {
+  using namespace llvm::VPlanPatternMatch;
+  if (VF.isScalable())
+    return;
+
+  SmallVector<VPInterleaveRecipe *> StoreGroups;
+  for (auto &R : *Plan.getVectorLoopRegion()->getEntryBasicBlock()) {
+    if (match(&R, m_BranchOnCount(m_VPValue(), m_VPValue())) ||
+        isa<VPCanonicalIVPHIRecipe>(&R))
----------------
alexey-bataev wrote:

```suggestion
    if (isa<VPCanonicalIVPHIRecipe>(&R) ||
        match(&R, m_BranchOnCount(m_VPValue(), m_VPValue())))
```


https://github.com/llvm/llvm-project/pull/106441