Revert "[LV]: Teach LV to recursively (de)interleave. (#89018)"

This reverts commit ccfe0de.

This breaks LLVM build on AArch64 SVE Linux buildbots
https://lab.llvm.org/buildbot/#/builders/143/builds/4462
https://lab.llvm.org/buildbot/#/builders/17/builds/4902
https://lab.llvm.org/buildbot/#/builders/4/builds/4399
https://lab.llvm.org/buildbot/#/builders/41/builds/4299

Author: omjavaid

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -3489,10 +3489,10 @@ bool LoopVectorizationCostModel::interleavedAccessCanBeWidened(
   if (hasIrregularType(ScalarTy, DL))
     return false;
 
-  // For scalable vectors, the only interleave factor currently supported
-  // must be power of 2 since we require the (de)interleave2 intrinsics
-  // instead of shufflevectors.
-  if (VF.isScalable() && !isPowerOf2_32(InterleaveFactor))
+  // We currently only know how to emit interleave/deinterleave with
+  // Factor=2 for scalable vectors. This is purely an implementation
+  // limit.
+  if (VF.isScalable() && InterleaveFactor != 2)
     return false;
 
   // If the group involves a non-integral pointer, we may not be able to
@@ -9193,9 +9193,9 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
                      CM.getWideningDecision(IG->getInsertPos(), VF) ==
                          LoopVectorizationCostModel::CM_Interleave);
       // For scalable vectors, the only interleave factor currently supported
-      // must be power of 2 since we require the (de)interleave2 intrinsics
-      // instead of shufflevectors.
-      assert((!Result || !VF.isScalable() || isPowerOf2_32(IG->getFactor())) &&
+      // is 2 since we require the (de)interleave2 intrinsics instead of
+      // shufflevectors.
+      assert((!Result || !VF.isScalable() || IG->getFactor() == 2) &&
              "Unsupported interleave factor for scalable vectors");
       return Result;
     };

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -2789,21 +2789,10 @@ static Value *interleaveVectors(IRBuilderBase &Builder, ArrayRef<Value *> Vals,
   // Scalable vectors cannot use arbitrary shufflevectors (only splats), so
   // must use intrinsics to interleave.
   if (VecTy->isScalableTy()) {
-    assert(isPowerOf2_32(Factor) && "Unsupported interleave factor for "
-                                    "scalable vectors, must be power of 2");
-    SmallVector<Value *> InterleavingValues(Vals);
-    // When interleaving, the number of values will be shrunk until we have the
-    // single final interleaved value.
-    auto *InterleaveTy = cast<VectorType>(InterleavingValues[0]->getType());
-    for (unsigned Midpoint = Factor / 2; Midpoint > 0; Midpoint /= 2) {
-      InterleaveTy = VectorType::getDoubleElementsVectorType(InterleaveTy);
-      for (unsigned I = 0; I < Midpoint; ++I)
-        InterleavingValues[I] = Builder.CreateIntrinsic(
-            InterleaveTy, Intrinsic::vector_interleave2,
-            {InterleavingValues[I], InterleavingValues[Midpoint + I]},
-            /*FMFSource=*/nullptr, Name);
-    }
-    return InterleavingValues[0];
+    VectorType *WideVecTy = VectorType::getDoubleElementsVectorType(VecTy);
+    return Builder.CreateIntrinsic(WideVecTy, Intrinsic::vector_interleave2,
+                                   Vals,
+                                   /*FMFSource=*/nullptr, Name);
   }
 
   // Fixed length. Start by concatenating all vectors into a wide vector.
@@ -2889,11 +2878,15 @@ void VPInterleaveRecipe::execute(VPTransformState &State) {
                           &InterleaveFactor](Value *MaskForGaps) -> Value * {
     if (State.VF.isScalable()) {
       assert(!MaskForGaps && "Interleaved groups with gaps are not supported.");
-      assert(isPowerOf2_32(InterleaveFactor) &&
+      assert(InterleaveFactor == 2 &&
              "Unsupported deinterleave factor for scalable vectors");
       auto *ResBlockInMask = State.get(BlockInMask);
-      SmallVector<Value *> Ops(InterleaveFactor, ResBlockInMask);
-      return interleaveVectors(State.Builder, Ops, "interleaved.mask");
+      SmallVector<Value *, 2> Ops = {ResBlockInMask, ResBlockInMask};
+      auto *MaskTy = VectorType::get(State.Builder.getInt1Ty(),
+                                     State.VF.getKnownMinValue() * 2, true);
+      return State.Builder.CreateIntrinsic(
+          MaskTy, Intrinsic::vector_interleave2, Ops,
+          /*FMFSource=*/nullptr, "interleaved.mask");
     }
 
     if (!BlockInMask)
@@ -2933,48 +2926,22 @@ void VPInterleaveRecipe::execute(VPTransformState &State) {
     ArrayRef<VPValue *> VPDefs = definedValues();
     const DataLayout &DL = State.CFG.PrevBB->getDataLayout();
     if (VecTy->isScalableTy()) {
-      assert(isPowerOf2_32(InterleaveFactor) &&
+      assert(InterleaveFactor == 2 &&
              "Unsupported deinterleave factor for scalable vectors");
 
-      // Scalable vectors cannot use arbitrary shufflevectors (only splats),
-      // so must use intrinsics to deinterleave.
-      SmallVector<Value *> DeinterleavedValues(InterleaveFactor);
-      DeinterleavedValues[0] = NewLoad;
-      // For the case of InterleaveFactor > 2, we will have to do recursive
-      // deinterleaving, because the current available deinterleave intrinsic
-      // supports only Factor of 2, otherwise it will bailout after first
-      // iteration.
-      // When deinterleaving, the number of values will double until we
-      // have "InterleaveFactor".
-      for (unsigned NumVectors = 1; NumVectors < InterleaveFactor;
-           NumVectors *= 2) {
-        // Deinterleave the elements within the vector
-        SmallVector<Value *> TempDeinterleavedValues(NumVectors);
-        for (unsigned I = 0; I < NumVectors; ++I) {
-          auto *DiTy = DeinterleavedValues[I]->getType();
-          TempDeinterleavedValues[I] = State.Builder.CreateIntrinsic(
-              Intrinsic::vector_deinterleave2, DiTy, DeinterleavedValues[I],
-              /*FMFSource=*/nullptr, "strided.vec");
-        }
-        // Extract the deinterleaved values:
-        for (unsigned I = 0; I < 2; ++I)
-          for (unsigned J = 0; J < NumVectors; ++J)
-            DeinterleavedValues[NumVectors * I + J] =
-                State.Builder.CreateExtractValue(TempDeinterleavedValues[J], I);
-      }
-
-#ifndef NDEBUG
-      for (Value *Val : DeinterleavedValues)
-        assert(Val && "NULL Deinterleaved Value");
-#endif
-      for (unsigned I = 0, J = 0; I < InterleaveFactor; ++I) {
+        // Scalable vectors cannot use arbitrary shufflevectors (only splats),
+        // so must use intrinsics to deinterleave.
+      Value *DI = State.Builder.CreateIntrinsic(
+          Intrinsic::vector_deinterleave2, VecTy, NewLoad,
+          /*FMFSource=*/nullptr, "strided.vec");
+      unsigned J = 0;
+      for (unsigned I = 0; I < InterleaveFactor; ++I) {
         Instruction *Member = Group->getMember(I);
-        Value *StridedVec = DeinterleavedValues[I];
-        if (!Member) {
-          // This value is not needed as it's not used
-          static_cast<Instruction *>(StridedVec)->eraseFromParent();
+
+        if (!Member)
           continue;
-        }
+
+        Value *StridedVec = State.Builder.CreateExtractValue(DI, I);
         // If this member has different type, cast the result type.
         if (Member->getType() != ScalarTy) {
           VectorType *OtherVTy = VectorType::get(Member->getType(), State.VF);