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

[via llvm-commits]

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@@ -1994,3 +1997,124 @@ 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();
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ayalz wrote:

nit: pass in VF's fixed value, and check if `IG->getFactor() == VF && IG->getNumMembers() == VF`, as documented?

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