[RISCV] Support extraction of misaligned subvectors

[frasercrmck]

Summary

This patch extends the support for RVV EXTRACT_SUBVECTOR to cover those
which don't align to a vector register boundary. It accomplishes this by
extracting the nearest register-sized subvector (a subregister
operation), then sliding the vector down with VSLIDEDOWN and extracting
the subvector from the first position (a COPY operation).

Since this procedure involves the use of VSCALE and multiplication, the
handling of such operations is done during lowering to simplify the
implementation and make use of DAG combining. This necessitated moving
some helper functions from RISCVISelDAGToDAG to RISCVTargetLowering.

[frasercrmck]

Just noticed I forgot to custom-lower float extracts and inserts in D96972. Will sort that tomorrow.

[craig.topper]

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

806

I kind of wonder if we should remove this division and multiply all the case values by 8. Right now we don't really verify that the KnownMinValue is divisible by 8 without remainder

2243

Should we start using RVVBitsPerBlock for 64's like this?

[frasercrmck]

• rebase
• use RVVBitsPerBlock instead of hard-coded 64

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

806

Probably a good idea, yes. That's why I hacked in getRegClassIDForVecVT in a previous patch which treats i1 separately. This was just moved from RISCVISelDAGToDAG, so I'm thinking it'd be better to fix that up afterwards? Then it can receive testing in isolation.

2243

Yes, good suggestion.

[frasercrmck]

• add support (and tests) for floating-point vectors

[craig.topper]

LGTM

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

806

We can do it afterwards.

[frasercrmck]

• rebase on main

[frasercrmck]

• rebase
• fix up some rebase issues

llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp

 //===-- RISCVISelDAGToDAG.cpp - A dag to dag inst selector for RISCV ------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines an instruction selector for the RISCV target.
 //
 //===----------------------------------------------------------------------===//
 
 #include "RISCVISelDAGToDAG.h"
 #include "MCTargetDesc/RISCVMCTargetDesc.h"
 #include "MCTargetDesc/RISCVMatInt.h"
+#include "RISCVISelLowering.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/IR/IntrinsicsRISCV.h"
 #include "llvm/Support/Alignment.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/KnownBits.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 
for (RISCVMatInt::Inst &Inst : Seq) {
 
     // Only the first instruction has X0 as its source.
     SrcReg = SDValue(Result, 0);
   }
 
   return Result;
 }
 
-static RISCVVLMUL getLMUL(MVT VT) {
-  switch (VT.getSizeInBits().getKnownMinValue() / 8) {
-  default:
-    llvm_unreachable("Invalid LMUL.");
-  case 1:
-    return RISCVVLMUL::LMUL_F8;
-  case 2:
-    return RISCVVLMUL::LMUL_F4;
-  case 4:
-    return RISCVVLMUL::LMUL_F2;
-  case 8:
-    return RISCVVLMUL::LMUL_1;
-  case 16:
-    return RISCVVLMUL::LMUL_2;
-  case 32:
-    return RISCVVLMUL::LMUL_4;
-  case 64:
-    return RISCVVLMUL::LMUL_8;
-  }
-}
-
-static unsigned getRegClassIDForLMUL(RISCVVLMUL LMul) {
-  switch (LMul) {
-  default:
-    llvm_unreachable("Invalid LMUL.");
-  case RISCVVLMUL::LMUL_F8:
-  case RISCVVLMUL::LMUL_F4:
-  case RISCVVLMUL::LMUL_F2:
-  case RISCVVLMUL::LMUL_1:
-    return RISCV::VRRegClassID;
-  case RISCVVLMUL::LMUL_2:
-    return RISCV::VRM2RegClassID;
-  case RISCVVLMUL::LMUL_4:
-    return RISCV::VRM4RegClassID;
-  case RISCVVLMUL::LMUL_8:
-    return RISCV::VRM8RegClassID;
-  }
-}
-
-static unsigned getSubregIndexByMVT(MVT VT, unsigned Index) {
-  RISCVVLMUL LMUL = getLMUL(VT);
-  if (LMUL == RISCVVLMUL::LMUL_F8 || LMUL == RISCVVLMUL::LMUL_F4 ||
-      LMUL == RISCVVLMUL::LMUL_F2 || LMUL == RISCVVLMUL::LMUL_1) {
-    static_assert(RISCV::sub_vrm1_7 == RISCV::sub_vrm1_0 + 7,
-                  "Unexpected subreg numbering");
-    return RISCV::sub_vrm1_0 + Index;
-  } else if (LMUL == RISCVVLMUL::LMUL_2) {
-    static_assert(RISCV::sub_vrm2_3 == RISCV::sub_vrm2_0 + 3,
-                  "Unexpected subreg numbering");
-    return RISCV::sub_vrm2_0 + Index;
-  } else if (LMUL == RISCVVLMUL::LMUL_4) {
-    static_assert(RISCV::sub_vrm4_1 == RISCV::sub_vrm4_0 + 1,
-                  "Unexpected subreg numbering");
-    return RISCV::sub_vrm4_0 + Index;
-  }
-  llvm_unreachable("Invalid vector type.");
-}
-
 static SDValue createTupleImpl(SelectionDAG &CurDAG, ArrayRef<SDValue> Regs,
                                unsigned RegClassID, unsigned SubReg0) {
   assert(Regs.size() >= 2 && Regs.size() <= 8);
 
   SDLoc DL(Regs[0]);
   SmallVector<SDValue, 8> Ops;
 
   Ops.push_back(CurDAG.getTargetConstant(RegClassID, DL, MVT::i32));

 
 void RISCVDAGToDAGISel::selectVLSEG(SDNode *Node, bool IsMasked,
                                     bool IsStrided) {
   SDLoc DL(Node);
   unsigned NF = Node->getNumValues() - 1;
   MVT VT = Node->getSimpleValueType(0);
   unsigned ScalarSize = VT.getScalarSizeInBits();
   MVT XLenVT = Subtarget->getXLenVT();
-  RISCVVLMUL LMUL = getLMUL(VT);
+  RISCVVLMUL LMUL = RISCVTargetLowering::getLMUL(VT);
   SDValue SEW = CurDAG->getTargetConstant(ScalarSize, DL, XLenVT);
   unsigned CurOp = 2;
   SmallVector<SDValue, 7> Operands;
   if (IsMasked) {
     SmallVector<SDValue, 8> Regs(Node->op_begin() + CurOp,
                                  Node->op_begin() + CurOp + NF);
     SDValue MaskedOff = createTuple(*CurDAG, Regs, NF, LMUL);
     Operands.push_back(MaskedOff);
     CurOp += NF;
   }
   Operands.push_back(Node->getOperand(CurOp++)); // Base pointer.
   if (IsStrided)
     Operands.push_back(Node->getOperand(CurOp++)); // Stride.
   if (IsMasked)
     Operands.push_back(Node->getOperand(CurOp++)); // Mask.
   Operands.push_back(Node->getOperand(CurOp++));   // VL.
   Operands.push_back(SEW);
   Operands.push_back(Node->getOperand(0)); // Chain.
   const RISCV::VLSEGPseudo *P =
       RISCV::getVLSEGPseudo(NF, IsMasked, IsStrided, /*FF*/ false, ScalarSize,
                             static_cast<unsigned>(LMUL));
   SDNode *Load =
       CurDAG->getMachineNode(P->Pseudo, DL, MVT::Untyped, MVT::Other, Operands);
   SDValue SuperReg = SDValue(Load, 0);
-  for (unsigned I = 0; I < NF; ++I)
+  for (unsigned I = 0; I < NF; ++I) {
+    unsigned SubRegIdx = RISCVTargetLowering::getSubregIndexByMVT(VT, I);
     ReplaceUses(SDValue(Node, I),
-                CurDAG->getTargetExtractSubreg(getSubregIndexByMVT(VT, I), DL,
-                                               VT, SuperReg));
+                CurDAG->getTargetExtractSubreg(SubRegIdx, DL, VT, SuperReg));
+  }
 
   ReplaceUses(SDValue(Node, NF), SDValue(Load, 1));
   CurDAG->RemoveDeadNode(Node);
 }
 
 void RISCVDAGToDAGISel::selectVLSEGFF(SDNode *Node, bool IsMasked) {
   SDLoc DL(Node);
   unsigned NF = Node->getNumValues() - 2; // Do not count VL and Chain.
   MVT VT = Node->getSimpleValueType(0);
   MVT XLenVT = Subtarget->getXLenVT();
   unsigned ScalarSize = VT.getScalarSizeInBits();
-  RISCVVLMUL LMUL = getLMUL(VT);
+  RISCVVLMUL LMUL = RISCVTargetLowering::getLMUL(VT);
   SDValue SEW = CurDAG->getTargetConstant(ScalarSize, DL, XLenVT);
 
   unsigned CurOp = 2;
   SmallVector<SDValue, 7> Operands;
   if (IsMasked) {
     SmallVector<SDValue, 8> Regs(Node->op_begin() + CurOp,
                                  Node->op_begin() + CurOp + NF);
     SDValue MaskedOff = createTuple(*CurDAG, Regs, NF, LMUL);
const RISCV::VLSEGPseudo *P =
       RISCV::getVLSEGPseudo(NF, IsMasked, /*Strided*/ false, /*FF*/ true,
                             ScalarSize, static_cast<unsigned>(LMUL));
   SDNode *Load = CurDAG->getMachineNode(P->Pseudo, DL, MVT::Untyped, MVT::Other,
                                         MVT::Glue, Operands);
   SDNode *ReadVL = CurDAG->getMachineNode(RISCV::PseudoReadVL, DL, XLenVT,
                                           /*Glue*/ SDValue(Load, 2));
 
   SDValue SuperReg = SDValue(Load, 0);
-  for (unsigned I = 0; I < NF; ++I)
+  for (unsigned I = 0; I < NF; ++I) {
+    unsigned SubRegIdx = RISCVTargetLowering::getSubregIndexByMVT(VT, I);
     ReplaceUses(SDValue(Node, I),
-                CurDAG->getTargetExtractSubreg(getSubregIndexByMVT(VT, I), DL,
-                                               VT, SuperReg));
+                CurDAG->getTargetExtractSubreg(SubRegIdx, DL, VT, SuperReg));
+  }
 
   ReplaceUses(SDValue(Node, NF), SDValue(ReadVL, 0));   // VL
   ReplaceUses(SDValue(Node, NF + 1), SDValue(Load, 1)); // Chain
   CurDAG->RemoveDeadNode(Node);
 }
 
 void RISCVDAGToDAGISel::selectVLXSEG(SDNode *Node, bool IsMasked,
                                      bool IsOrdered) {
   SDLoc DL(Node);
   unsigned NF = Node->getNumValues() - 1;
   MVT VT = Node->getSimpleValueType(0);
   unsigned ScalarSize = VT.getScalarSizeInBits();
   MVT XLenVT = Subtarget->getXLenVT();
-  RISCVVLMUL LMUL = getLMUL(VT);
+  RISCVVLMUL LMUL = RISCVTargetLowering::getLMUL(VT);
   SDValue SEW = CurDAG->getTargetConstant(ScalarSize, DL, XLenVT);
   unsigned CurOp = 2;
   SmallVector<SDValue, 7> Operands;
   if (IsMasked) {
     SmallVector<SDValue, 8> Regs(Node->op_begin() + CurOp,
                                  Node->op_begin() + CurOp + NF);
     SDValue MaskedOff = createTuple(*CurDAG, Regs, NF, LMUL);
     Operands.push_back(MaskedOff);
     CurOp += NF;
   }
   Operands.push_back(Node->getOperand(CurOp++)); // Base pointer.
   Operands.push_back(Node->getOperand(CurOp++)); // Index.
   MVT IndexVT = Operands.back()->getSimpleValueType(0);
   if (IsMasked)
     Operands.push_back(Node->getOperand(CurOp++)); // Mask.
   Operands.push_back(Node->getOperand(CurOp++));   // VL.
   Operands.push_back(SEW);
   Operands.push_back(Node->getOperand(0)); // Chain.
 
-  RISCVVLMUL IndexLMUL = getLMUL(IndexVT);
+  RISCVVLMUL IndexLMUL = RISCVTargetLowering::getLMUL(IndexVT);
   unsigned IndexScalarSize = IndexVT.getScalarSizeInBits();
   const RISCV::VLXSEGPseudo *P = RISCV::getVLXSEGPseudo(
       NF, IsMasked, IsOrdered, IndexScalarSize, static_cast<unsigned>(LMUL),
       static_cast<unsigned>(IndexLMUL));
   SDNode *Load =
       CurDAG->getMachineNode(P->Pseudo, DL, MVT::Untyped, MVT::Other, Operands);
   SDValue SuperReg = SDValue(Load, 0);
-  for (unsigned I = 0; I < NF; ++I)
+  for (unsigned I = 0; I < NF; ++I) {
+    unsigned SubRegIdx = RISCVTargetLowering::getSubregIndexByMVT(VT, I);
     ReplaceUses(SDValue(Node, I),
-                CurDAG->getTargetExtractSubreg(getSubregIndexByMVT(VT, I), DL,
-                                               VT, SuperReg));
+                CurDAG->getTargetExtractSubreg(SubRegIdx, DL, VT, SuperReg));
+  }
 
   ReplaceUses(SDValue(Node, NF), SDValue(Load, 1));
   CurDAG->RemoveDeadNode(Node);
 }
 
 void RISCVDAGToDAGISel::selectVSSEG(SDNode *Node, bool IsMasked,
                                     bool IsStrided) {
   SDLoc DL(Node);
   unsigned NF = Node->getNumOperands() - 4;
   if (IsStrided)
     NF--;
   if (IsMasked)
     NF--;
   MVT VT = Node->getOperand(2)->getSimpleValueType(0);
   unsigned ScalarSize = VT.getScalarSizeInBits();
   MVT XLenVT = Subtarget->getXLenVT();
-  RISCVVLMUL LMUL = getLMUL(VT);
+  RISCVVLMUL LMUL = RISCVTargetLowering::getLMUL(VT);
   SDValue SEW = CurDAG->getTargetConstant(ScalarSize, DL, XLenVT);
   SmallVector<SDValue, 8> Regs(Node->op_begin() + 2, Node->op_begin() + 2 + NF);
   SDValue StoreVal = createTuple(*CurDAG, Regs, NF, LMUL);
   SmallVector<SDValue, 7> Operands;
   Operands.push_back(StoreVal);
   unsigned CurOp = 2 + NF;
   Operands.push_back(Node->getOperand(CurOp++)); // Base pointer.
   if (IsStrided)
void RISCVDAGToDAGISel::selectVSXSEG(SDNode *Node, bool IsMasked,
                                      bool IsOrdered) {
   SDLoc DL(Node);
   unsigned NF = Node->getNumOperands() - 5;
   if (IsMasked)
     --NF;
   MVT VT = Node->getOperand(2)->getSimpleValueType(0);
   unsigned ScalarSize = VT.getScalarSizeInBits();
   MVT XLenVT = Subtarget->getXLenVT();
-  RISCVVLMUL LMUL = getLMUL(VT);
+  RISCVVLMUL LMUL = RISCVTargetLowering::getLMUL(VT);
   SDValue SEW = CurDAG->getTargetConstant(ScalarSize, DL, XLenVT);
   SmallVector<SDValue, 7> Operands;
   SmallVector<SDValue, 8> Regs(Node->op_begin() + 2, Node->op_begin() + 2 + NF);
   SDValue StoreVal = createTuple(*CurDAG, Regs, NF, LMUL);
   Operands.push_back(StoreVal);
   unsigned CurOp = 2 + NF;
   Operands.push_back(Node->getOperand(CurOp++)); // Base pointer.
   Operands.push_back(Node->getOperand(CurOp++)); // Index.
   MVT IndexVT = Operands.back()->getSimpleValueType(0);
   if (IsMasked)
     Operands.push_back(Node->getOperand(CurOp++)); // Mask.
   Operands.push_back(Node->getOperand(CurOp++));   // VL.
   Operands.push_back(SEW);
   Operands.push_back(Node->getOperand(0)); // Chain.
 
-  RISCVVLMUL IndexLMUL = getLMUL(IndexVT);
+  RISCVVLMUL IndexLMUL = RISCVTargetLowering::getLMUL(IndexVT);
   unsigned IndexScalarSize = IndexVT.getScalarSizeInBits();
   const RISCV::VSXSEGPseudo *P = RISCV::getVSXSEGPseudo(
       NF, IsMasked, IsOrdered, IndexScalarSize, static_cast<unsigned>(LMUL),
       static_cast<unsigned>(IndexLMUL));
   SDNode *Store =
       CurDAG->getMachineNode(P->Pseudo, DL, Node->getValueType(0), Operands);
   ReplaceNode(Node, Store);
 }
 
-static unsigned getRegClassIDForVecVT(MVT VT) {
-  if (VT.getVectorElementType() == MVT::i1)
-    return RISCV::VRRegClassID;
-  return getRegClassIDForLMUL(getLMUL(VT));
-}
-
-// Attempt to decompose a subvector insert/extract between VecVT and
-// SubVecVT via subregister indices. Returns the subregister index that
-// can perform the subvector insert/extract with the given element index, as
-// well as the index corresponding to any leftover subvectors that must be
-// further inserted/extracted within the register class for SubVecVT.
-static std::pair<unsigned, unsigned>
-decomposeSubvectorInsertExtractToSubRegs(MVT VecVT, MVT SubVecVT,
-                                         unsigned InsertExtractIdx,
-                                         const RISCVRegisterInfo *TRI) {
-  static_assert((RISCV::VRM8RegClassID > RISCV::VRM4RegClassID &&
-                 RISCV::VRM4RegClassID > RISCV::VRM2RegClassID &&
-                 RISCV::VRM2RegClassID > RISCV::VRRegClassID),
-                "Register classes not ordered");
-  unsigned VecRegClassID = getRegClassIDForVecVT(VecVT);
-  unsigned SubRegClassID = getRegClassIDForVecVT(SubVecVT);
-  // Try to compose a subregister index that takes us from the incoming
-  // LMUL>1 register class down to the outgoing one. At each step we half
-  // the LMUL:
-  //   nxv16i32@12 -> nxv2i32: sub_vrm4_1_then_sub_vrm2_1_then_sub_vrm1_0
-  // Note that this is not guaranteed to find a subregister index, such as
-  // when we are extracting from one VR type to another.
-  unsigned SubRegIdx = RISCV::NoSubRegister;
-  for (const unsigned RCID :
-       {RISCV::VRM4RegClassID, RISCV::VRM2RegClassID, RISCV::VRRegClassID})
-    if (VecRegClassID > RCID && SubRegClassID <= RCID) {
-      VecVT = VecVT.getHalfNumVectorElementsVT();
-      bool IsHi =
-          InsertExtractIdx >= VecVT.getVectorElementCount().getKnownMinValue();
-      SubRegIdx = TRI->composeSubRegIndices(SubRegIdx,
-                                            getSubregIndexByMVT(VecVT, IsHi));
-      if (IsHi)
-        InsertExtractIdx -= VecVT.getVectorElementCount().getKnownMinValue();
-    }
-  return {SubRegIdx, InsertExtractIdx};
-}
 
 void RISCVDAGToDAGISel::Select(SDNode *Node) {
   // If we have a custom node, we have already selected.
   if (Node->isMachineOpcode()) {
     LLVM_DEBUG(dbgs() << "== "; Node->dump(CurDAG); dbgs() << "\n");
     Node->setNodeId(-1);
     return;
   }
case ISD::INSERT_SUBVECTOR: {
     MVT SubVecVT = Node->getOperand(1).getSimpleValueType();
 
     // TODO: This method of selecting INSERT_SUBVECTOR should work
     // with any type of insertion (fixed <-> scalable) but we don't yet
     // correctly identify the canonical register class for fixed-length types.
     // For now, keep the two paths separate.
     if (VT.isScalableVector() && SubVecVT.isScalableVector()) {
       bool IsFullVecReg = false;
-      switch (getLMUL(SubVecVT)) {
+      switch (RISCVTargetLowering::getLMUL(SubVecVT)) {
       default:
         break;
       case RISCVVLMUL::LMUL_1:
       case RISCVVLMUL::LMUL_2:
       case RISCVVLMUL::LMUL_4:
       case RISCVVLMUL::LMUL_8:
         IsFullVecReg = true;
         break;
       }
 
       // If the subvector doesn't occupy a full vector register then we can't
       // insert it purely using subregister manipulation. We must not clobber
       // the untouched elements (say, in the upper half of the VR register).
       if (!IsFullVecReg)
         break;
 
       const auto *TRI = Subtarget->getRegisterInfo();
       unsigned SubRegIdx;
       std::tie(SubRegIdx, Idx) =
-          decomposeSubvectorInsertExtractToSubRegs(VT, SubVecVT, Idx, TRI);
+          RISCVTargetLowering::decomposeSubvectorInsertExtractToSubRegs(
+              VT, SubVecVT, Idx, TRI);
 
       // If the Idx hasn't been completely eliminated then this is a subvector
-      // extract which doesn't naturally align to a vector register. These must
+      // insert which doesn't naturally align to a vector register. These must
       // be handled using instructions to manipulate the vector registers.
       if (Idx != 0)
         break;
 
       SDNode *NewNode = CurDAG->getMachineNode(
           TargetOpcode::INSERT_SUBREG, DL, VT, V, SubV,
           CurDAG->getTargetConstant(SubRegIdx, DL, Subtarget->getXLenVT()));
       return ReplaceNode(Node, NewNode);
     }
 
     if (VT.isScalableVector() && SubVecVT.isFixedLengthVector()) {
       // Bail when not a "cast" like insert_subvector.
       if (Idx != 0)
         break;
       if (!Node->getOperand(0).isUndef())
         break;
 
-      unsigned RegClassID = getRegClassIDForVecVT(VT);
+      unsigned RegClassID = RISCVTargetLowering::getRegClassIDForVecVT(VT);
 
       SDValue RC =
           CurDAG->getTargetConstant(RegClassID, DL, Subtarget->getXLenVT());
       SDNode *NewNode = CurDAG->getMachineNode(TargetOpcode::COPY_TO_REGCLASS,
                                                DL, VT, SubV, RC);
       ReplaceNode(Node, NewNode);
       return;
     }
     break;
   }
   case ISD::EXTRACT_SUBVECTOR: {
     SDValue V = Node->getOperand(0);
     auto Idx = Node->getConstantOperandVal(1);
     MVT InVT = Node->getOperand(0).getSimpleValueType();
     SDLoc DL(V);
 
     // TODO: This method of selecting EXTRACT_SUBVECTOR should work
     // with any type of extraction (fixed <-> scalable) but we don't yet
     // correctly identify the canonical register class for fixed-length types.
     // For now, keep the two paths separate.
     if (VT.isScalableVector() && InVT.isScalableVector()) {
       const auto *TRI = Subtarget->getRegisterInfo();
       unsigned SubRegIdx;
       std::tie(SubRegIdx, Idx) =
-          decomposeSubvectorInsertExtractToSubRegs(InVT, VT, Idx, TRI);
+          RISCVTargetLowering::decomposeSubvectorInsertExtractToSubRegs(
+              InVT, VT, Idx, TRI);
 
       // If the Idx hasn't been completely eliminated then this is a subvector
       // extract which doesn't naturally align to a vector register. These must
       // be handled using instructions to manipulate the vector registers.
       if (Idx != 0)
         break;
 
       // If we haven't set a SubRegIdx, then we must be going between LMUL<=1
       // types (VR -> VR). This can be done as a copy.
       if (SubRegIdx == RISCV::NoSubRegister) {
-        unsigned InRegClassID = getRegClassIDForVecVT(InVT);
-        assert(getRegClassIDForVecVT(VT) == RISCV::VRRegClassID &&
+        unsigned InRegClassID =
+            RISCVTargetLowering::getRegClassIDForVecVT(InVT);
+        assert(RISCVTargetLowering::getRegClassIDForVecVT(VT) ==
+                   RISCV::VRRegClassID &&
                InRegClassID == RISCV::VRRegClassID &&
                "Unexpected subvector extraction");
         SDValue RC =
             CurDAG->getTargetConstant(InRegClassID, DL, Subtarget->getXLenVT());
         SDNode *NewNode = CurDAG->getMachineNode(TargetOpcode::COPY_TO_REGCLASS,
                                                  DL, VT, V, RC);
         return ReplaceNode(Node, NewNode);
       }
       SDNode *NewNode = CurDAG->getMachineNode(
           TargetOpcode::EXTRACT_SUBREG, DL, VT, V,
           CurDAG->getTargetConstant(SubRegIdx, DL, Subtarget->getXLenVT()));
       return ReplaceNode(Node, NewNode);
     }
 
     if (VT.isFixedLengthVector() && InVT.isScalableVector()) {
       // Bail when not a "cast" like extract_subvector.
       if (Idx != 0)
         break;
 
-      unsigned InRegClassID = getRegClassIDForVecVT(InVT);
+      unsigned InRegClassID = RISCVTargetLowering::getRegClassIDForVecVT(InVT);
 
       SDValue RC =
           CurDAG->getTargetConstant(InRegClassID, DL, Subtarget->getXLenVT());
       SDNode *NewNode =
           CurDAG->getMachineNode(TargetOpcode::COPY_TO_REGCLASS, DL, VT, V, RC);
       ReplaceNode(Node, NewNode);
       return;
     }

llvm/lib/Target/RISCV/RISCVISelLowering.h

 #define LLVM_LIB_TARGET_RISCV_RISCVISELLOWERING_H
 
 #include "RISCV.h"
 #include "llvm/CodeGen/SelectionDAG.h"
 #include "llvm/CodeGen/TargetLowering.h"
 
 namespace llvm {
 class RISCVSubtarget;
+struct RISCVRegisterInfo;
 namespace RISCVISD {
 enum NodeType : unsigned {
   FIRST_NUMBER = ISD::BUILTIN_OP_END,
   RET_FLAG,
   URET_FLAG,
   SRET_FLAG,
   MRET_FLAG,
   CALL,
public:
 
   /// Returns true if the target allows unaligned memory accesses of the
   /// specified type.
   bool allowsMisalignedMemoryAccesses(
       EVT VT, unsigned AddrSpace = 0, Align Alignment = Align(1),
       MachineMemOperand::Flags Flags = MachineMemOperand::MONone,
       bool *Fast = nullptr) const override;
 
+  static RISCVVLMUL getLMUL(MVT VT);
+  static unsigned getRegClassIDForLMUL(RISCVVLMUL LMul);
+  static unsigned getSubregIndexByMVT(MVT VT, unsigned Index);
+  static unsigned getRegClassIDForVecVT(MVT VT);
+  static std::pair<unsigned, unsigned>
+  decomposeSubvectorInsertExtractToSubRegs(MVT VecVT, MVT SubVecVT,
+                                           unsigned InsertExtractIdx,
+                                           const RISCVRegisterInfo *TRI);
+
 private:
   void analyzeInputArgs(MachineFunction &MF, CCState &CCInfo,
                         const SmallVectorImpl<ISD::InputArg> &Ins,
                         bool IsRet) const;
   void analyzeOutputArgs(MachineFunction &MF, CCState &CCInfo,
                          const SmallVectorImpl<ISD::OutputArg> &Outs,
                          bool IsRet, CallLoweringInfo *CLI) const;
 
SDValue lowerVectorMaskExt(SDValue Op, SelectionDAG &DAG,
                              int64_t ExtTrueVal) const;
   SDValue lowerVectorMaskTrunc(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerINSERT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerEXTRACT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerINTRINSIC_WO_CHAIN(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerINTRINSIC_W_CHAIN(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerVECREDUCE(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerFPVECREDUCE(SDValue Op, SelectionDAG &DAG) const;
+  SDValue lowerEXTRACT_SUBVECTOR(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerFixedLengthVectorLoadToRVV(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerFixedLengthVectorStoreToRVV(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerFixedLengthVectorSetccToRVV(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerFixedLengthVectorLogicOpToRVV(SDValue Op, SelectionDAG &DAG,
                                              unsigned MaskOpc,
                                              unsigned VecOpc) const;
   SDValue lowerFixedLengthVectorSelectToRVV(SDValue Op,
                                             SelectionDAG &DAG) const;

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

for (MVT VT : IntVecVTs) {
       setOperationAction(ISD::VECREDUCE_ADD, VT, Custom);
       setOperationAction(ISD::VECREDUCE_AND, VT, Custom);
       setOperationAction(ISD::VECREDUCE_OR, VT, Custom);
       setOperationAction(ISD::VECREDUCE_XOR, VT, Custom);
       setOperationAction(ISD::VECREDUCE_SMAX, VT, Custom);
       setOperationAction(ISD::VECREDUCE_SMIN, VT, Custom);
       setOperationAction(ISD::VECREDUCE_UMAX, VT, Custom);
       setOperationAction(ISD::VECREDUCE_UMIN, VT, Custom);
+
+      setOperationAction(ISD::EXTRACT_SUBVECTOR, VT, Custom);
     }
 
     // Expand various CCs to best match the RVV ISA, which natively supports UNE
     // but no other unordered comparisons, and supports all ordered comparisons
     // except ONE. Additionally, we expand GT,OGT,GE,OGE for optimization
     // purposes; they are expanded to their swapped-operand CCs (LT,OLT,LE,OLE),
     // and we pattern-match those back to the "original", swapping operands once
     // more. This way we catch both operations and both "vf" and "fv" forms with
case ISD::SETGE:
     return RISCV::BGE;
   case ISD::SETULT:
     return RISCV::BLTU;
   case ISD::SETUGE:
     return RISCV::BGEU;
   }
 }
 
+RISCVVLMUL RISCVTargetLowering::getLMUL(MVT VT) {
+  switch (VT.getSizeInBits().getKnownMinValue() / 8) {
+  default:
+    llvm_unreachable("Invalid LMUL.");
+  case 1:
+    return RISCVVLMUL::LMUL_F8;
+  case 2:
+    return RISCVVLMUL::LMUL_F4;
+  case 4:
+    return RISCVVLMUL::LMUL_F2;
+  case 8:
+    return RISCVVLMUL::LMUL_1;
+  case 16:
+    return RISCVVLMUL::LMUL_2;
+  case 32:
+    return RISCVVLMUL::LMUL_4;
+  case 64:
+    return RISCVVLMUL::LMUL_8;
+  }
+}
+
+unsigned RISCVTargetLowering::getRegClassIDForLMUL(RISCVVLMUL LMul) {
+  switch (LMul) {
+  default:
+    llvm_unreachable("Invalid LMUL.");
+  case RISCVVLMUL::LMUL_F8:
+  case RISCVVLMUL::LMUL_F4:
+  case RISCVVLMUL::LMUL_F2:
+  case RISCVVLMUL::LMUL_1:
+    return RISCV::VRRegClassID;
+  case RISCVVLMUL::LMUL_2:
+    return RISCV::VRM2RegClassID;
+  case RISCVVLMUL::LMUL_4:
+    return RISCV::VRM4RegClassID;
+  case RISCVVLMUL::LMUL_8:
+    return RISCV::VRM8RegClassID;
+  }
+}
+
+unsigned RISCVTargetLowering::getSubregIndexByMVT(MVT VT, unsigned Index) {
+  RISCVVLMUL LMUL = getLMUL(VT);
+  if (LMUL == RISCVVLMUL::LMUL_F8 || LMUL == RISCVVLMUL::LMUL_F4 ||
+      LMUL == RISCVVLMUL::LMUL_F2 || LMUL == RISCVVLMUL::LMUL_1) {
+    static_assert(RISCV::sub_vrm1_7 == RISCV::sub_vrm1_0 + 7,
+                  "Unexpected subreg numbering");
+    return RISCV::sub_vrm1_0 + Index;
+  }
+  if (LMUL == RISCVVLMUL::LMUL_2) {
+    static_assert(RISCV::sub_vrm2_3 == RISCV::sub_vrm2_0 + 3,
+                  "Unexpected subreg numbering");
+    return RISCV::sub_vrm2_0 + Index;
+  }
+  if (LMUL == RISCVVLMUL::LMUL_4) {
+    static_assert(RISCV::sub_vrm4_1 == RISCV::sub_vrm4_0 + 1,
+                  "Unexpected subreg numbering");
+    return RISCV::sub_vrm4_0 + Index;
+  }
+  llvm_unreachable("Invalid vector type.");
+}
+
+unsigned RISCVTargetLowering::getRegClassIDForVecVT(MVT VT) {
+  if (VT.getVectorElementType() == MVT::i1)
+    return RISCV::VRRegClassID;
+  return getRegClassIDForLMUL(getLMUL(VT));
+}
+
+// Attempt to decompose a subvector insert/extract between VecVT and
+// SubVecVT via subregister indices. Returns the subregister index that
+// can perform the subvector insert/extract with the given element index, as
+// well as the index corresponding to any leftover subvectors that must be
+// further inserted/extracted within the register class for SubVecVT.
+std::pair<unsigned, unsigned>
+RISCVTargetLowering::decomposeSubvectorInsertExtractToSubRegs(
+    MVT VecVT, MVT SubVecVT, unsigned InsertExtractIdx,
+    const RISCVRegisterInfo *TRI) {
+  static_assert((RISCV::VRM8RegClassID > RISCV::VRM4RegClassID &&
+                 RISCV::VRM4RegClassID > RISCV::VRM2RegClassID &&
+                 RISCV::VRM2RegClassID > RISCV::VRRegClassID),
+                "Register classes not ordered");
+  unsigned VecRegClassID = getRegClassIDForVecVT(VecVT);
+  unsigned SubRegClassID = getRegClassIDForVecVT(SubVecVT);
+  // Try to compose a subregister index that takes us from the incoming
+  // LMUL>1 register class down to the outgoing one. At each step we half
+  // the LMUL:
+  //   nxv16i32@12 -> nxv2i32: sub_vrm4_1_then_sub_vrm2_1_then_sub_vrm1_0
+  // Note that this is not guaranteed to find a subregister index, such as
+  // when we are extracting from one VR type to another.
+  unsigned SubRegIdx = RISCV::NoSubRegister;
+  for (const unsigned RCID :
+       {RISCV::VRM4RegClassID, RISCV::VRM2RegClassID, RISCV::VRRegClassID})
+    if (VecRegClassID > RCID && SubRegClassID <= RCID) {
+      VecVT = VecVT.getHalfNumVectorElementsVT();
+      bool IsHi =
+          InsertExtractIdx >= VecVT.getVectorElementCount().getKnownMinValue();
+      SubRegIdx = TRI->composeSubRegIndices(SubRegIdx,
+                                            getSubregIndexByMVT(VecVT, IsHi));
+      if (IsHi)
+        InsertExtractIdx -= VecVT.getVectorElementCount().getKnownMinValue();
+    }
+  return {SubRegIdx, InsertExtractIdx};
+}
+
 // Return the largest legal scalable vector type that matches VT's element type.
 static MVT getContainerForFixedLengthVector(SelectionDAG &DAG, MVT VT,
                                             const RISCVSubtarget &Subtarget) {
   assert(VT.isFixedLengthVector() &&
          DAG.getTargetLoweringInfo().isTypeLegal(VT) &&
          "Expected legal fixed length vector!");
 
   unsigned LMul = Subtarget.getLMULForFixedLengthVector(VT);
SDValue RISCVTargetLowering::LowerOperation(SDValue Op,
   case ISD::VECREDUCE_SMIN:
   case ISD::VECREDUCE_AND:
   case ISD::VECREDUCE_OR:
   case ISD::VECREDUCE_XOR:
     return lowerVECREDUCE(Op, DAG);
   case ISD::VECREDUCE_FADD:
   case ISD::VECREDUCE_SEQ_FADD:
     return lowerFPVECREDUCE(Op, DAG);
+  case ISD::EXTRACT_SUBVECTOR:
+    return lowerEXTRACT_SUBVECTOR(Op, DAG);
   case ISD::BUILD_VECTOR:
     return lowerBUILD_VECTOR(Op, DAG, Subtarget);
   case ISD::VECTOR_SHUFFLE:
     return lowerVECTOR_SHUFFLE(Op, DAG, Subtarget);
   case ISD::LOAD:
     return lowerFixedLengthVectorLoadToRVV(Op, DAG);
   case ISD::STORE:
     return lowerFixedLengthVectorStoreToRVV(Op, DAG);
std::tie(RVVOpcode, VectorVal, ScalarVal) =
       getRVVFPReductionOpAndOperands(Op, DAG, VecEltVT);
 
   SDValue ScalarSplat = DAG.getSplatVector(M1VT, DL, ScalarVal);
   SDValue Reduction = DAG.getNode(RVVOpcode, DL, M1VT, VectorVal, ScalarSplat);
   return DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, VecEltVT, Reduction,
                      DAG.getConstant(0, DL, Subtarget.getXLenVT()));
 }
 
+static MVT getLMUL1VT(MVT VT) {
+  assert(VT.getVectorElementType().getSizeInBits() <= 64 &&
+         "Unexpected vector MVT");
+  return MVT::getScalableVectorVT(
+      VT.getVectorElementType(),
+      RISCV::RVVBitsPerBlock / VT.getVectorElementType().getSizeInBits());
+}
+
+SDValue RISCVTargetLowering::lowerEXTRACT_SUBVECTOR(SDValue Op,
+                                                    SelectionDAG &DAG) const {
+  SDValue Vec = Op.getOperand(0);
+  MVT SubVecVT = Op.getSimpleValueType();
+  MVT VecVT = Vec.getSimpleValueType();
+
+  // TODO: Only handle scalable->scalable extracts for now, and revisit this
+  // for fixed-length vectors later.
+  if (!SubVecVT.isScalableVector() || !VecVT.isScalableVector())
+    return Op;
+
+  SDLoc DL(Op);
+  unsigned OrigIdx = Op.getConstantOperandVal(1);
+  const RISCVRegisterInfo *TRI = Subtarget.getRegisterInfo();
+
+  unsigned SubRegIdx, RemIdx;
+  std::tie(SubRegIdx, RemIdx) =
+      RISCVTargetLowering::decomposeSubvectorInsertExtractToSubRegs(
+          VecVT, SubVecVT, OrigIdx, TRI);
+
+  // If the Idx has been completely eliminated then this is a subvector extract
+  // which naturally aligns to a vector register. These can easily be handled
+  // using subregister manipulation.
+  if (RemIdx == 0)
+    return Op;
+
+  // Else we must shift our vector register directly to extract the subvector.
+  // Do this using VSLIDEDOWN.
+  MVT XLenVT = Subtarget.getXLenVT();
+
+  // Extract a subvector equal to the nearest full vector register type. This
+  // should resolve to a EXTRACT_SUBREG instruction.
+  unsigned AlignedIdx = OrigIdx - RemIdx;
+  MVT InterSubVT = getLMUL1VT(VecVT);
+  SDValue AlignedExtract =
+      DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, InterSubVT, Vec,
+                  DAG.getConstant(AlignedIdx, DL, XLenVT));
+
+  // Slide this vector register down by the desired number of elements in order
+  // to place the desired subvector starting at element 0.
+  SDValue SlidedownAmt = DAG.getConstant(RemIdx, DL, XLenVT);
+  // For scalable vectors this must be further multiplied by vscale.
+  SlidedownAmt = DAG.getNode(ISD::VSCALE, DL, XLenVT, SlidedownAmt);
+
+  SDValue Mask, VL;
+  std::tie(Mask, VL) = getDefaultScalableVLOps(InterSubVT, DL, DAG, Subtarget);
+  SDValue Slidedown = DAG.getNode(RISCVISD::VSLIDEDOWN_VL, DL, InterSubVT,
+                                  DAG.getUNDEF(InterSubVT), AlignedExtract,
+                                  SlidedownAmt, Mask, VL);
+
+  // Now the vector is in the right position, extract our final subvector. This
+  // should resolve to a COPY.
+  return DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, SubVecVT, Slidedown,
+                     DAG.getConstant(0, DL, XLenVT));
+}
+
 SDValue
 RISCVTargetLowering::lowerFixedLengthVectorLoadToRVV(SDValue Op,
                                                      SelectionDAG &DAG) const {
   auto *Load = cast<LoadSDNode>(Op);
 
   SDLoc DL(Op);
   MVT VT = Op.getSimpleValueType();
   MVT ContainerVT = getContainerForFixedLengthVector(DAG, VT, Subtarget);

llvm/test/CodeGen/RISCV/rvv/extract-subvector.ll

 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -mtriple riscv64 -mattr=+experimental-v -verify-machineinstrs < %s | FileCheck %s
+; RUN: llc -mtriple riscv64 -mattr=+m,+experimental-v -verify-machineinstrs < %s | FileCheck %s
 
 define <vscale x 4 x i32> @extract_nxv8i32_nxv4i32_0(<vscale x 8 x i32> %vec) {
 ; CHECK-LABEL: extract_nxv8i32_nxv4i32_0:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    # kill: def $v8m2 killed $v8m2 killed $v8m4
 ; CHECK-NEXT:    ret
   %c = call <vscale x 4 x i32> @llvm.experimental.vector.extract.nxv4i32.nxv8i32(<vscale x 8 x i32> %vec, i64 0)
   ret <vscale x 4 x i32> %c

 ; CHECK-LABEL: extract_nxv16i32_nxv1i32_0:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    # kill: def $v8 killed $v8 killed $v8m8
 ; CHECK-NEXT:    ret
   %c = call <vscale x 1 x i32> @llvm.experimental.vector.extract.nxv1i32.nxv16i32(<vscale x 16 x i32> %vec, i64 0)
   ret <vscale x 1 x i32> %c
 }
 
-; TODO: Extracts that don't align to a vector register are not yet supported.
-; In this case we want to extract the upper half of the lowest VR subregister
-; in the LMUL group.
-; define <vscale x 1 x i32> @extract_nxv16i32_nxv1i32_1(<vscale x 16 x i32> %vec) {
-;   %c = call <vscale x 1 x i32> @llvm.experimental.vector.extract.nxv1i32.nxv16i32(<vscale x 16 x i32> %vec, i64 1)
-;   ret <vscale x 1 x i32> %c
-; }
+define <vscale x 1 x i32> @extract_nxv16i32_nxv1i32_1(<vscale x 16 x i32> %vec) {
+; CHECK-LABEL: extract_nxv16i32_nxv1i32_1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    csrr a0, vlenb
+; CHECK-NEXT:    srli a0, a0, 3
+; CHECK-NEXT:    vsetvli a1, zero, e32,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v8, v8, a0
+; CHECK-NEXT:    ret
+  %c = call <vscale x 1 x i32> @llvm.experimental.vector.extract.nxv1i32.nxv16i32(<vscale x 16 x i32> %vec, i64 1)
+  ret <vscale x 1 x i32> %c
+}
+
+define <vscale x 1 x i32> @extract_nxv16i32_nxv1i32_3(<vscale x 16 x i32> %vec) {
+; CHECK-LABEL: extract_nxv16i32_nxv1i32_3:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    csrr a0, vlenb
+; CHECK-NEXT:    srli a0, a0, 3
+; CHECK-NEXT:    vsetvli a1, zero, e32,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v8, v9, a0
+; CHECK-NEXT:    ret
+  %c = call <vscale x 1 x i32> @llvm.experimental.vector.extract.nxv1i32.nxv16i32(<vscale x 16 x i32> %vec, i64 3)
+  ret <vscale x 1 x i32> %c
+}
+
+define <vscale x 1 x i32> @extract_nxv16i32_nxv1i32_15(<vscale x 16 x i32> %vec) {
+; CHECK-LABEL: extract_nxv16i32_nxv1i32_15:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    csrr a0, vlenb
+; CHECK-NEXT:    srli a0, a0, 3
+; CHECK-NEXT:    vsetvli a1, zero, e32,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v8, v15, a0
+; CHECK-NEXT:    ret
+  %c = call <vscale x 1 x i32> @llvm.experimental.vector.extract.nxv1i32.nxv16i32(<vscale x 16 x i32> %vec, i64 15)
+  ret <vscale x 1 x i32> %c
+}
 
 define <vscale x 1 x i32> @extract_nxv16i32_nxv1i32_2(<vscale x 16 x i32> %vec) {
 ; CHECK-LABEL: extract_nxv16i32_nxv1i32_2:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    vmv1r.v v8, v9
 ; CHECK-NEXT:    ret
   %c = call <vscale x 1 x i32> @llvm.experimental.vector.extract.nxv1i32.nxv16i32(<vscale x 16 x i32> %vec, i64 2)
   ret <vscale x 1 x i32> %c
 }
 
 define <vscale x 1 x i32> @extract_nxv2i32_nxv1i32_0(<vscale x 2 x i32> %vec) {
 ; CHECK-LABEL: extract_nxv2i32_nxv1i32_0:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    ret
   %c = call <vscale x 1 x i32> @llvm.experimental.vector.extract.nxv1i32.nxv2i32(<vscale x 2 x i32> %vec, i64 0)
   ret <vscale x 1 x i32> %c
 }
 
+define <vscale x 2 x i8> @extract_nxv32i8_nxv2i8_0(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv32i8_nxv2i8_0:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    # kill: def $v8 killed $v8 killed $v8m4
+; CHECK-NEXT:    ret
+  %c = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 0)
+  ret <vscale x 2 x i8> %c
+}
+
+define <vscale x 2 x i8> @extract_nxv32i8_nxv2i8_2(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv32i8_nxv2i8_2:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    csrr a0, vlenb
+; CHECK-NEXT:    srli a0, a0, 2
+; CHECK-NEXT:    vsetvli a1, zero, e8,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v8, v8, a0
+; CHECK-NEXT:    ret
+  %c = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 2)
+  ret <vscale x 2 x i8> %c
+}
+
+define <vscale x 2 x i8> @extract_nxv32i8_nxv2i8_4(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv32i8_nxv2i8_4:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    csrr a0, vlenb
+; CHECK-NEXT:    srli a0, a0, 1
+; CHECK-NEXT:    vsetvli a1, zero, e8,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v8, v8, a0
+; CHECK-NEXT:    ret
+  %c = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 4)
+  ret <vscale x 2 x i8> %c
+}
+
+define <vscale x 2 x i8> @extract_nxv32i8_nxv2i8_6(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv32i8_nxv2i8_6:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    csrr a0, vlenb
+; CHECK-NEXT:    srli a0, a0, 3
+; CHECK-NEXT:    addi a1, zero, 6
+; CHECK-NEXT:    mul a0, a0, a1
+; CHECK-NEXT:    vsetvli a1, zero, e8,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v8, v8, a0
+; CHECK-NEXT:    ret
+  %c = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 6)
+  ret <vscale x 2 x i8> %c
+}
+
+define <vscale x 2 x i8> @extract_nxv32i8_nxv2i8_8(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv32i8_nxv2i8_8:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vmv1r.v v8, v9
+; CHECK-NEXT:    ret
+  %c = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 8)
+  ret <vscale x 2 x i8> %c
+}
+
+define <vscale x 2 x i8> @extract_nxv32i8_nxv2i8_22(<vscale x 32 x i8> %vec) {
+; CHECK-LABEL: extract_nxv32i8_nxv2i8_22:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    csrr a0, vlenb
+; CHECK-NEXT:    srli a0, a0, 3
+; CHECK-NEXT:    addi a1, zero, 6
+; CHECK-NEXT:    mul a0, a0, a1
+; CHECK-NEXT:    vsetvli a1, zero, e8,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v8, v10, a0
+; CHECK-NEXT:    ret
+  %c = call <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 22)
+  ret <vscale x 2 x i8> %c
+}
+
+define <vscale x 1 x i8> @extract_nxv8i8_nxv1i8_7(<vscale x 8 x i8> %vec) {
+; CHECK-LABEL: extract_nxv8i8_nxv1i8_7:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    csrr a0, vlenb
+; CHECK-NEXT:    srli a0, a0, 3
+; CHECK-NEXT:    slli a1, a0, 3
+; CHECK-NEXT:    sub a0, a1, a0
+; CHECK-NEXT:    vsetvli a1, zero, e8,m1,ta,mu
+; CHECK-NEXT:    vslidedown.vx v8, v8, a0
+; CHECK-NEXT:    ret
+  %c = call <vscale x 1 x i8> @llvm.experimental.vector.extract.nxv1i8.nxv8i8(<vscale x 8 x i8> %vec, i64 7)
+  ret <vscale x 1 x i8> %c
+}
+
+declare <vscale x 1 x i8> @llvm.experimental.vector.extract.nxv1i8.nxv8i8(<vscale x 8 x i8> %vec, i64 %idx)
+
+declare <vscale x 2 x i8> @llvm.experimental.vector.extract.nxv2i8.nxv32i8(<vscale x 32 x i8> %vec, i64 %idx)
+
 declare <vscale x 1 x i32> @llvm.experimental.vector.extract.nxv1i32.nxv2i32(<vscale x 2 x i32> %vec, i64 %idx)
 
 declare <vscale x 2 x i32> @llvm.experimental.vector.extract.nxv2i32.nxv8i32(<vscale x 8 x i32> %vec, i64 %idx)
 declare <vscale x 4 x i32> @llvm.experimental.vector.extract.nxv4i32.nxv8i32(<vscale x 8 x i32> %vec, i64 %idx)
 
 declare <vscale x 1 x i32> @llvm.experimental.vector.extract.nxv1i32.nxv16i32(<vscale x 16 x i32> %vec, i64 %idx)
 declare <vscale x 2 x i32> @llvm.experimental.vector.extract.nxv2i32.nxv16i32(<vscale x 16 x i32> %vec, i64 %idx)
 declare <vscale x 4 x i32> @llvm.experimental.vector.extract.nxv4i32.nxv16i32(<vscale x 16 x i32> %vec, i64 %idx)
 declare <vscale x 8 x i32> @llvm.experimental.vector.extract.nxv8i32.nxv16i32(<vscale x 16 x i32> %vec, i64 %idx)