[AArch64][SVE] Implement masked load intrinsics

[kmclaughlin]

Summary

Adds support for codegen of masked loads, with non-extending,
zero-extending and sign-extending variants.

[dmgreen]

Sam has been looking at extending masked loads and stores in D68337 and related patches. There looks like there would be some overlap with this, especially in the target independent parts. Make sure you co-ordinate with him.

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

10453

I'm not convinced that just because a sext load is legal and a masked load is legal, that a sext masked load is always legal.

llvm/lib/Target/AArch64/AArch64SVEInstrInfo.td

1077

What if the passthru isn't undef?

llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h

151

This can handle all masked loads? Of any type, extended into any other type, with any alignment?

153

This patch doesn't handle stores yet.

llvm/lib/Target/AArch64/SVEInstrFormats.td

296

Can this just use "undef"?

[kmclaughlin]

• Rebased patch, removed extra sext & zext combine from DAGCombine which are no longer necessary
• Added isVectorLoadExtDesirable to AArch64ISelLowering
• Added more checks to isLegalMaskedLoad
• Changed SVEUndef to SVEDup0Undef, handling undef or all zeros
• Changed SelectionDAG::getConstant to return SPLAT_VECTOR instead of BUILD_VECTOR for scalable types

[kmclaughlin]

Thanks for reviewing this, @dmgreen! I have updated the patch to make use of the changes to DAGCombine introduced by D68337.

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

10453

Removed, as this patch can also use tryToFoldExtOfMaskedLoad for sext & zext masked loads.

llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h

151

I have added checks on types we can handle here

153

Removed!

[dmgreen]

Thanks!

It looks like the only supported parameter of the PassThru here is a splat of 0 or undef. This might get in the way of IR level optimisation that could try to producing a masked load with different passthru, which would then fail to select. The ARM backed added a custom lowering to turn this case into a select of the loaded value and the passthru. Like this, which was further modified in later commits:
https://github.com/llvm/llvm-project/commit/b325c057322ce14b5c561d8ac49508adab7649e5#diff-b853ecd5d5e0f73c2c093ffb5b4f2fbbR8855
That way you only have to check on the zero, not undef. I'm not sure if there is support yet for vector selects in the SVE codegen?

I was also expecting something that says "setOperationAction(ISD::MLOAD, VT, Legal)" somewhere, but I guess that's already the default?

llvm/lib/Target/AArch64/SVEInstrFormats.td

4753

Can you explain why is this pseudo is needed, exactly? I feel that using pseudos is often the wrong solution to a problem (it may be required here, I'm just sure why exactly).

We currently seem to generate ld1b (for example), over ldnf1b. Is there ever a time that we expect to generate a nf load?

[kmclaughlin]

• Removed unnecessary pseudo from SVEInstrFormats.td

[kmclaughlin]

In D68877#1717820, @dmgreen wrote:

I'm not sure if there is support yet for vector selects in the SVE codegen?

There is not yet support for vector selects, so for this patch the intention was that any passthru which is not all zero or undef would result in a selection failure.
Do you think it would acceptable to handle different passthrus in a future patch which also implements vector selects for SVE?

llvm/lib/Target/AArch64/SVEInstrFormats.td

4753

The pseudo was a workaround that was added downstream for non-faulting loads, but it is not needed here.

[huntergr]

I was also expecting something that says "setOperationAction(ISD::MLOAD, VT, Legal)" somewhere, but I guess that's already the default?

It is; we will need to set the operation action for supported VTs to 'Custom' once we have codegen for vselects in order to handle any passthru values which aren't undef or zero (which you've already noticed as missing in the review), but the operation itself is legal once it gets through type legalization.

There's a separate mechanism to handle illegal masked loads/stores in the ScalarizeMaskedMemIntrin pass before lowering to a SelectionDAG. Scalarization needs to create new basic blocks for a loop over the vector elements, which isn't easy after lowering. The TargetTransformInfo::isLegalMaskedLoad (or Store) functions are what determine whether scalarization takes place or not for a given target.

[dmgreen]

In D68877#1718729, @kmclaughlin wrote:

There is not yet support for vector selects, so for this patch the intention was that any passthru which is not all zero or undef would result in a selection failure.
Do you think it would acceptable to handle different passthrus in a future patch which also implements vector selects for SVE?

Yeah OK. That makes sense. I remember the same chicken and egg from MVE. We ended up doing them the other way around there. Can you try and add a FIXME comment somewhere?

Otherwise LGTM.

llvm/lib/Target/AArch64/SVEInstrFormats.td

4753

Righteo. We know where to find it if it turns out we do need them.

[Yi-Hong.Lyu]

This comment was removed by Yi-Hong.Lyu.

llvm/include/llvm/CodeGen/SelectionDAG.h

if (Op.getOpcode() == ISD::UNDEF) {
              "greater than the vector element type!");
       return getNode(ISD::UNDEF, SDLoc(), VT);
     }
 
     SmallVector<SDValue, 16> Ops(VT.getVectorNumElements(), Op);
     return getNode(ISD::BUILD_VECTOR, DL, VT, Ops);
   }
 
+  // Return a splat ISD::SPLAT_VECTOR node, consisting of Op splatted to all
+  // elements.
+  SDValue getSplatVector(EVT VT, const SDLoc &DL, SDValue Op) {
+    if (Op.getOpcode() == ISD::UNDEF) {
+      assert((VT.getVectorElementType() == Op.getValueType() ||
+              (VT.isInteger() &&
+               VT.getVectorElementType().bitsLE(Op.getValueType()))) &&
+             "A splatted value must have a width equal or (for integers) "
+             "greater than the vector element type!");
+      return getNode(ISD::UNDEF, SDLoc(), VT);
+    }
+    return getNode(ISD::SPLAT_VECTOR, DL, VT, Op);
+  }
+
   /// Returns an ISD::VECTOR_SHUFFLE node semantically equivalent to
   /// the shuffle node in input but with swapped operands.
   ///
   /// Example: shuffle A, B, <0,5,2,7> -> shuffle B, A, <4,1,6,3>
   SDValue getCommutedVectorShuffle(const ShuffleVectorSDNode &SV);
 
   /// Convert Op, which must be of float type, to the
   /// float type VT, by either extending or rounding (by truncation).

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

while (!TLI.isLoadExtLegalOrCustom(ExtType, SplitDstVT, SplitSrcVT) &&
          SplitSrcVT.getVectorNumElements() > 1) {
     SplitDstVT = DAG.GetSplitDestVTs(SplitDstVT).first;
     SplitSrcVT = DAG.GetSplitDestVTs(SplitSrcVT).first;
   }
 
   if (!TLI.isLoadExtLegalOrCustom(ExtType, SplitDstVT, SplitSrcVT))
     return SDValue();
 
+  assert(!DstVT.isScalableVector() && "Unexpected scalable vector type");
+
   SDLoc DL(N);
   const unsigned NumSplits =
       DstVT.getVectorNumElements() / SplitDstVT.getVectorNumElements();
   const unsigned Stride = SplitSrcVT.getStoreSize();
   SmallVector<SDValue, 4> Loads;
   SmallVector<SDValue, 4> Chains;
 
   SDValue BasePtr = LN0->getBasePtr();
if (ISD::isEXTLoad(N0.getNode()) &&
     CombineTo(N0.getNode(), ExtLoad, ExtLoad.getValue(1));
     AddToWorklist(ExtLoad.getNode());
     return SDValue(N, 0);   // Return N so it doesn't get rechecked!
   }
   // fold (sext_inreg (zextload x)) -> (sextload x) iff load has one use
   if (ISD::isZEXTLoad(N0.getNode()) && ISD::isUNINDEXEDLoad(N0.getNode()) &&
       N0.hasOneUse() &&
       EVT == cast<LoadSDNode>(N0)->getMemoryVT() &&
       ((!LegalOperations && cast<LoadSDNode>(N0)->isSimple()) &&
        TLI.isLoadExtLegal(ISD::SEXTLOAD, VT, EVT))) {
     LoadSDNode *LN0 = cast<LoadSDNode>(N0);
     SDValue ExtLoad = DAG.getExtLoad(ISD::SEXTLOAD, SDLoc(N), VT,
                                      LN0->getChain(),
                                      LN0->getBasePtr(), EVT,
                                      LN0->getMemOperand());
     CombineTo(N, ExtLoad);
     CombineTo(N0.getNode(), ExtLoad, ExtLoad.getValue(1));

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

SDValue SelectionDAG::getConstant(const ConstantInt &Val, const SDLoc &DL,
   if (!N) {
     N = newSDNode<ConstantSDNode>(isT, isO, Elt, EltVT);
     CSEMap.InsertNode(N, IP);
     InsertNode(N);
     NewSDValueDbgMsg(SDValue(N, 0), "Creating constant: ", this);
   }
 
   SDValue Result(N, 0);
-  if (VT.isVector())
+  if (VT.isScalableVector())
+    Result = getSplatVector(VT, DL, Result);
+  else if (VT.isVector())
     Result = getSplatBuildVector(VT, DL, Result);
 
   return Result;
 }
 
 SDValue SelectionDAG::getIntPtrConstant(uint64_t Val, const SDLoc &DL,
                                         bool isTarget) {
   return getConstant(Val, DL, TLI->getPointerTy(getDataLayout()), isTarget);

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

void SelectionDAGBuilder::visitMaskedLoad(const CallInst &I, bool IsExpanding) {
   if (!Alignment)
     Alignment = DAG.getEVTAlignment(VT);
 
   AAMDNodes AAInfo;
   I.getAAMetadata(AAInfo);
   const MDNode *Ranges = I.getMetadata(LLVMContext::MD_range);
 
   // Do not serialize masked loads of constant memory with anything.
-  bool AddToChain =
-      !AA || !AA->pointsToConstantMemory(MemoryLocation(
-                 PtrOperand,
-                 LocationSize::precise(
+  MemoryLocation ML;
+  if (VT.isScalableVector())
+    ML = MemoryLocation(PtrOperand);
+  else
+    ML = MemoryLocation(PtrOperand, LocationSize::precise(
                            DAG.getDataLayout().getTypeStoreSize(I.getType())),
-                 AAInfo));
+                           AAInfo);
+  bool AddToChain = !AA || !AA->pointsToConstantMemory(ML);
+
   SDValue InChain = AddToChain ? DAG.getRoot() : DAG.getEntryNode();
 
   MachineMemOperand *MMO =
     DAG.getMachineFunction().
     getMachineMemOperand(MachinePointerInfo(PtrOperand),
                           MachineMemOperand::MOLoad,  VT.getStoreSize(),
                           Alignment, AAInfo, Ranges);
 

llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp

public:
   }
 
   template<int Width>
   bool SelectAddrModeXRO(SDValue N, SDValue &Base, SDValue &Offset,
                          SDValue &SignExtend, SDValue &DoShift) {
     return SelectAddrModeXRO(N, Width / 8, Base, Offset, SignExtend, DoShift);
   }
 
+  bool SelectDupZeroOrUndef(SDValue N) {
+    switch(N->getOpcode()) {
+    case ISD::UNDEF:
+      return true;
+    case AArch64ISD::DUP:
+    case ISD::SPLAT_VECTOR: {
+      auto Opnd0 = N->getOperand(0);
+      if (auto CN = dyn_cast<ConstantSDNode>(Opnd0))
+        if (CN->isNullValue())
+          return true;
+      if (auto CN = dyn_cast<ConstantFPSDNode>(Opnd0))
+        if (CN->isZero())
+          return true;
+    }
+    default:
+      break;
+    }
+
+    return false;
+  }
 
   /// Form sequences of consecutive 64/128-bit registers for use in NEON
   /// instructions making use of a vector-list (e.g. ldN, tbl). Vecs must have
   /// between 1 and 4 elements. If it contains a single element that is returned
   /// unchanged; otherwise a REG_SEQUENCE value is returned.
   SDValue createDTuple(ArrayRef<SDValue> Vecs);
   SDValue createQTuple(ArrayRef<SDValue> Vecs);
 

llvm/lib/Target/AArch64/AArch64ISelLowering.h

unsigned getInlineAsmMemConstraint(StringRef ConstraintCode) const override {
     if (ConstraintCode == "Q")
       return InlineAsm::Constraint_Q;
     // FIXME: clang has code for 'Ump', 'Utf', 'Usa', and 'Ush' but these are
     //        followed by llvm_unreachable so we'll leave them unimplemented in
     //        the backend for now.
     return TargetLowering::getInlineAsmMemConstraint(ConstraintCode);
   }
 
+  bool isVectorLoadExtDesirable(SDValue ExtVal) const override;
   bool isUsedByReturnOnly(SDNode *N, SDValue &Chain) const override;
   bool mayBeEmittedAsTailCall(const CallInst *CI) const override;
   bool getIndexedAddressParts(SDNode *Op, SDValue &Base, SDValue &Offset,
                               ISD::MemIndexedMode &AM, bool &IsInc,
                               SelectionDAG &DAG) const;
   bool getPreIndexedAddressParts(SDNode *N, SDValue &Base, SDValue &Offset,
                                  ISD::MemIndexedMode &AM,
                                  SelectionDAG &DAG) const override;

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

case Intrinsic::eh_recoverfp: {
     if (!Fn)
       report_fatal_error(
           "llvm.eh.recoverfp must take a function as the first argument");
     return IncomingFPOp;
   }
   }
 }
 
+bool AArch64TargetLowering::isVectorLoadExtDesirable(SDValue ExtVal) const {
+  return ExtVal.getValueType().isScalableVector();
+}
+
 // Custom lower trunc store for v4i8 vectors, since it is promoted to v4i16.
 static SDValue LowerTruncateVectorStore(SDLoc DL, StoreSDNode *ST,
                                         EVT VT, EVT MemVT,
                                         SelectionDAG &DAG) {
   assert(VT.isVector() && "VT should be a vector type");
   assert(MemVT == MVT::v4i8 && VT == MVT::v4i16);
 
   SDValue Value = ST->getValue();

llvm/lib/Target/AArch64/AArch64InstrInfo.td

 def SDT_AArch64TLSDescCallSeq : SDTypeProfile<0,1,
                                           [SDTCisPtrTy<0>]>;
 
 def SDT_AArch64WrapperLarge : SDTypeProfile<1, 4,
                                         [SDTCisVT<0, i64>, SDTCisVT<1, i32>,
                                          SDTCisSameAs<1, 2>, SDTCisSameAs<1, 3>,
                                          SDTCisSameAs<1, 4>]>;
 
+// non-extending masked load fragment.
+def nonext_masked_load :
+  PatFrag<(ops node:$ptr, node:$pred, node:$def),
+          (masked_ld node:$ptr, node:$pred, node:$def), [{
+  return cast<MaskedLoadSDNode>(N)->getExtensionType() == ISD::NON_EXTLOAD;
+}]>;
+// sign extending masked load fragments.
+def asext_masked_load :
+  PatFrag<(ops node:$ptr, node:$pred, node:$def),
+          (masked_ld node:$ptr, node:$pred, node:$def),[{
+  return cast<MaskedLoadSDNode>(N)->getExtensionType() == ISD::EXTLOAD ||
+         cast<MaskedLoadSDNode>(N)->getExtensionType() == ISD::SEXTLOAD;
+}]>;
+def asext_masked_load_i8 :
+  PatFrag<(ops node:$ptr, node:$pred, node:$def),
+          (asext_masked_load node:$ptr, node:$pred, node:$def), [{
+  return cast<MaskedLoadSDNode>(N)->getMemoryVT().getScalarType() == MVT::i8;
+}]>;
+def asext_masked_load_i16 :
+  PatFrag<(ops node:$ptr, node:$pred, node:$def),
+          (asext_masked_load node:$ptr, node:$pred, node:$def), [{
+  return cast<MaskedLoadSDNode>(N)->getMemoryVT().getScalarType() == MVT::i16;
+}]>;
+def asext_masked_load_i32 :
+  PatFrag<(ops node:$ptr, node:$pred, node:$def),
+          (asext_masked_load node:$ptr, node:$pred, node:$def), [{
+  return cast<MaskedLoadSDNode>(N)->getMemoryVT().getScalarType() == MVT::i32;
+}]>;
+// zero extending masked load fragments.
+def zext_masked_load :
+  PatFrag<(ops node:$ptr, node:$pred, node:$def),
+          (masked_ld node:$ptr, node:$pred, node:$def), [{
+  return cast<MaskedLoadSDNode>(N)->getExtensionType() == ISD::ZEXTLOAD;
+}]>;
+def zext_masked_load_i8 :
+  PatFrag<(ops node:$ptr, node:$pred, node:$def),
+          (zext_masked_load node:$ptr, node:$pred, node:$def), [{
+  return cast<MaskedLoadSDNode>(N)->getMemoryVT().getScalarType() == MVT::i8;
+}]>;
+def zext_masked_load_i16 :
+  PatFrag<(ops node:$ptr, node:$pred, node:$def),
+          (zext_masked_load node:$ptr, node:$pred, node:$def), [{
+  return cast<MaskedLoadSDNode>(N)->getMemoryVT().getScalarType() == MVT::i16;
+}]>;
+def zext_masked_load_i32 :
+  PatFrag<(ops node:$ptr, node:$pred, node:$def),
+          (zext_masked_load node:$ptr, node:$pred, node:$def), [{
+  return cast<MaskedLoadSDNode>(N)->getMemoryVT().getScalarType() == MVT::i32;
+}]>;
 
 // Node definitions.
 def AArch64adrp          : SDNode<"AArch64ISD::ADRP", SDTIntUnaryOp, []>;
 def AArch64adr           : SDNode<"AArch64ISD::ADR", SDTIntUnaryOp, []>;
 def AArch64addlow        : SDNode<"AArch64ISD::ADDlow", SDTIntBinOp, []>;
 def AArch64LOADgot       : SDNode<"AArch64ISD::LOADgot", SDTIntUnaryOp>;
 def AArch64callseq_start : SDNode<"ISD::CALLSEQ_START",
                                 SDCallSeqStart<[ SDTCisVT<0, i32>,

llvm/lib/Target/AArch64/AArch64SVEInstrInfo.td

 
   def : Pat<(nxv2f64 (bitconvert (nxv16i8 ZPR:$src))), (nxv2f64 ZPR:$src)>;
   def : Pat<(nxv2f64 (bitconvert (nxv8i16 ZPR:$src))), (nxv2f64 ZPR:$src)>;
   def : Pat<(nxv2f64 (bitconvert (nxv4i32 ZPR:$src))), (nxv2f64 ZPR:$src)>;
   def : Pat<(nxv2f64 (bitconvert (nxv2i64 ZPR:$src))), (nxv2f64 ZPR:$src)>;
   def : Pat<(nxv2f64 (bitconvert (nxv8f16 ZPR:$src))), (nxv2f64 ZPR:$src)>;
   def : Pat<(nxv2f64 (bitconvert (nxv4f32 ZPR:$src))), (nxv2f64 ZPR:$src)>;
 
+  // Add more complex addressing modes here as required
+  multiclass pred_load<ValueType Ty, ValueType PredTy, SDPatternOperator Load,
+                        Instruction RegImmInst> {
+
+    def _default_z : Pat<(Ty (Load  GPR64:$base, (PredTy PPR:$gp), (SVEDup0Undef))),
+                         (RegImmInst PPR:$gp, GPR64:$base, (i64 0))>;
+  }
+
+  // 2-element contiguous loads
+  defm : pred_load<nxv2i64, nxv2i1, zext_masked_load_i8,   LD1B_D_IMM>;
+  defm : pred_load<nxv2i64, nxv2i1, asext_masked_load_i8,  LD1SB_D_IMM>;
+  defm : pred_load<nxv2i64, nxv2i1, zext_masked_load_i16,  LD1H_D_IMM>;
+  defm : pred_load<nxv2i64, nxv2i1, asext_masked_load_i16, LD1SH_D_IMM>;
+  defm : pred_load<nxv2i64, nxv2i1, zext_masked_load_i32,  LD1W_D_IMM>;
+  defm : pred_load<nxv2i64, nxv2i1, asext_masked_load_i32, LD1SW_D_IMM>;
+  defm : pred_load<nxv2i64, nxv2i1, nonext_masked_load,    LD1D_IMM>;
+  defm : pred_load<nxv2f16, nxv2i1, nonext_masked_load,    LD1H_D_IMM>;
+  defm : pred_load<nxv2f32, nxv2i1, nonext_masked_load,    LD1W_D_IMM>;
+  defm : pred_load<nxv2f64, nxv2i1, nonext_masked_load,    LD1D_IMM>;
+
+  // 4-element contiguous loads
+  defm : pred_load<nxv4i32, nxv4i1, zext_masked_load_i8,   LD1B_S_IMM>;
+  defm : pred_load<nxv4i32, nxv4i1, asext_masked_load_i8,  LD1SB_S_IMM>;
+  defm : pred_load<nxv4i32, nxv4i1, zext_masked_load_i16,  LD1H_S_IMM>;
+  defm : pred_load<nxv4i32, nxv4i1, asext_masked_load_i16, LD1SH_S_IMM>;
+  defm : pred_load<nxv4i32, nxv4i1, nonext_masked_load,    LD1W_IMM>;
+  defm : pred_load<nxv4f16, nxv4i1, nonext_masked_load,    LD1H_S_IMM>;
+  defm : pred_load<nxv4f32, nxv4i1, nonext_masked_load,    LD1W_IMM>;
+
+  // 8-element contiguous loads
+  defm : pred_load<nxv8i16, nxv8i1, zext_masked_load_i8,  LD1B_H_IMM>;
+  defm : pred_load<nxv8i16, nxv8i1, asext_masked_load_i8, LD1SB_H_IMM>;
+  defm : pred_load<nxv8i16, nxv8i1, nonext_masked_load,   LD1H_IMM>;
+  defm : pred_load<nxv8f16, nxv8i1, nonext_masked_load,   LD1H_IMM>;
+
+  // 16-element contiguous loads
+  defm : pred_load<nxv16i8, nxv16i1, nonext_masked_load, LD1B_IMM>;
+
 }
 
 let Predicates = [HasSVE2] in {
   // SVE2 integer multiply-add (indexed)
   defm MLA_ZZZI : sve2_int_mla_by_indexed_elem<0b01, 0b0, "mla">;
   defm MLS_ZZZI : sve2_int_mla_by_indexed_elem<0b01, 0b1, "mls">;
 
   // SVE2 saturating multiply-add high (indexed)

llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h

public:
   void getUnrollingPreferences(Loop *L, ScalarEvolution &SE,
                                TTI::UnrollingPreferences &UP);
 
   Value *getOrCreateResultFromMemIntrinsic(IntrinsicInst *Inst,
                                            Type *ExpectedType);
 
   bool getTgtMemIntrinsic(IntrinsicInst *Inst, MemIntrinsicInfo &Info);
 
+  bool isLegalMaskedLoad(Type *DataType, MaybeAlign Alignment) {
+    if (!isa<VectorType>(DataType) || !ST->hasSVE())
+      return false;
+
+    Type *Ty = DataType->getVectorElementType();
+    if (Ty->isHalfTy() || Ty->isFloatTy() || Ty->isDoubleTy())
+      return true;
+
+    if (Ty->isIntegerTy(8) || Ty->isIntegerTy(16) ||
+        Ty->isIntegerTy(32) || Ty->isIntegerTy(64))
+      return true;
+
+    return false;
+  }
+
   int getInterleavedMemoryOpCost(unsigned Opcode, Type *VecTy, unsigned Factor,
                                  ArrayRef<unsigned> Indices, unsigned Alignment,
                                  unsigned AddressSpace,
                                  bool UseMaskForCond = false,
                                  bool UseMaskForGaps = false);
 
   bool
   shouldConsiderAddressTypePromotion(const Instruction &I,

llvm/lib/Target/AArch64/SVEInstrFormats.td

 : Pat<(vtd (op vt1:$Op1)),
       (inst $Op1)>;
 
 class SVE_3_Op_Pat<ValueType vtd, SDPatternOperator op, ValueType vt1,
                    ValueType vt2, ValueType vt3, Instruction inst>
 : Pat<(vtd (op vt1:$Op1, vt2:$Op2, vt3:$Op3)),
       (inst $Op1, $Op2, $Op3)>;
 
+def SVEDup0Undef : ComplexPattern<i64, 0, "SelectDupZeroOrUndef", []>;
+
 //===----------------------------------------------------------------------===//
 // SVE Predicate Misc Group
 //===----------------------------------------------------------------------===//
 
 class sve_int_pfalse<bits<6> opc, string asm>
 : I<(outs PPR8:$Pd), (ins),
   asm, "\t$Pd",
   "",
multiclass sve_mem_cld_si_base<bits<4> dtype, bit nf, string asm,
   def _REAL : sve_mem_cld_si_base<dtype, nf, asm, listty>;
 
   def : InstAlias<asm # "\t$Zt, $Pg/z, [$Rn]",
                   (!cast<Instruction>(NAME # _REAL) zprty:$Zt, PPR3bAny:$Pg, GPR64sp:$Rn, 0), 0>;
   def : InstAlias<asm # "\t$Zt, $Pg/z, [$Rn, $imm4, mul vl]",
                   (!cast<Instruction>(NAME # _REAL) zprty:$Zt, PPR3bAny:$Pg, GPR64sp:$Rn, simm4s1:$imm4), 0>;
   def : InstAlias<asm # "\t$Zt, $Pg/z, [$Rn]",
                   (!cast<Instruction>(NAME # _REAL) listty:$Zt, PPR3bAny:$Pg, GPR64sp:$Rn, 0), 1>;
+
+  // We need a layer of indirection because early machine code passes balk at
+  // physical register (i.e. FFR) uses that have no previous definition.
+  let hasSideEffects = 1, hasNoSchedulingInfo = 1, mayLoad = 1 in {
+  def "" : Pseudo<(outs listty:$Zt), (ins PPR3bAny:$Pg, GPR64sp:$Rn, simm4s1:$imm4), []>,
+           PseudoInstExpansion<(!cast<Instruction>(NAME # _REAL) listty:$Zt, PPR3bAny:$Pg, GPR64sp:$Rn, simm4s1:$imm4)>;
+  }
 }
 
 multiclass sve_mem_cld_si<bits<4> dtype, string asm, RegisterOperand listty,
                           ZPRRegOp zprty>
 : sve_mem_cld_si_base<dtype, 0, asm, listty, zprty>;
 
 class sve_mem_cldnt_si_base<bits<2> msz, string asm, RegisterOperand VecList>
 : I<(outs VecList:$Zt), (ins PPR3bAny:$Pg, GPR64sp:$Rn, simm4s1:$imm4),

llvm/test/CodeGen/AArch64/sve-masked-ldst-nonext.ll

+; RUN: llc -mtriple=aarch64--linux-gnu -mattr=+sve < %s | FileCheck %s
+
+;
+; Masked Loads
+;
+
+define <vscale x 2 x i64> @masked_load_nxv2i64(<vscale x 2 x i64> *%a, <vscale x 2 x i1> %mask) {
+; CHECK-LABEL: masked_load_nxv2i64:
+; CHECK: ld1d { [[IN:z[0-9]+]].d }, [[PG:p[0-9]+]]/z, [x0]
+  %load = call <vscale x 2 x i64> @llvm.masked.load.nxv2i64(<vscale x 2 x i64> *%a, i32 8, <vscale x 2 x i1> %mask, <vscale x 2 x i64> undef)
+  ret <vscale x 2 x i64> %load
+}
+
+define <vscale x 4 x i32> @masked_load_nxv4i32(<vscale x 4 x i32> *%a, <vscale x 4 x i1> %mask) {
+; CHECK-LABEL: masked_load_nxv4i32:
+; CHECK: ld1w { [[IN:z[0-9]+]].s }, [[PG:p[0-9]+]]/z, [x0]
+  %load = call <vscale x 4 x i32> @llvm.masked.load.nxv4i32(<vscale x 4 x i32> *%a, i32 4, <vscale x 4 x i1> %mask, <vscale x 4 x i32> undef)
+  ret <vscale x 4 x i32> %load
+}
+
+define <vscale x 8 x i16> @masked_load_nxv8i16(<vscale x 8 x i16> *%a, <vscale x 8 x i1> %mask) {
+; CHECK-LABEL: masked_load_nxv8i16:
+; CHECK: ld1h { [[IN:z[0-9]+]].h }, [[PG:p[0-9]+]]/z, [x0]
+  %load = call <vscale x 8 x i16> @llvm.masked.load.nxv8i16(<vscale x 8 x i16> *%a, i32 2, <vscale x 8 x i1> %mask, <vscale x 8 x i16> undef)
+  ret <vscale x 8 x i16> %load
+}
+
+define <vscale x 16 x i8> @masked_load_nxv16i8(<vscale x 16 x i8> *%a, <vscale x 16 x i1> %mask) {
+; CHECK-LABEL: masked_load_nxv16i8:
+; CHECK: ld1b { [[IN:z[0-9]+]].b }, [[PG:p[0-9]+]]/z, [x0]
+  %load = call <vscale x 16 x i8> @llvm.masked.load.nxv16i8(<vscale x 16 x i8> *%a, i32 1, <vscale x 16 x i1> %mask, <vscale x 16 x i8> undef)
+  ret <vscale x 16 x i8> %load
+}
+
+define <vscale x 2 x double> @masked_load_nxv2f64(<vscale x 2 x double> *%a, <vscale x 2 x i1> %mask) {
+; CHECK-LABEL: masked_load_nxv2f64:
+; CHECK: ld1d { [[IN:z[0-9]+]].d }, [[PG:p[0-9]+]]/z, [x0]
+  %load = call <vscale x 2 x double> @llvm.masked.load.nxv2f64(<vscale x 2 x double> *%a, i32 8, <vscale x 2 x i1> %mask, <vscale x 2 x double> undef)
+  ret <vscale x 2 x double> %load
+}
+
+define <vscale x 2 x float> @masked_load_nxv2f32(<vscale x 2 x float> *%a, <vscale x 2 x i1> %mask) {
+; CHECK-LABEL: masked_load_nxv2f32:
+; CHECK: ld1w { [[IN:z[0-9]+]].d }, [[PG:p[0-9]+]]/z, [x0]
+  %load = call <vscale x 2 x float> @llvm.masked.load.nxv2f32(<vscale x 2 x float> *%a, i32 4, <vscale x 2 x i1> %mask, <vscale x 2 x float> undef)
+  ret <vscale x 2 x float> %load
+}
+
+define <vscale x 2 x half> @masked_load_nxv2f16(<vscale x 2 x half> *%a, <vscale x 2 x i1> %mask) {
+; CHECK-LABEL: masked_load_nxv2f16:
+; CHECK: ld1h { [[IN:z[0-9]+]].d }, [[PG:p[0-9]+]]/z, [x0]
+  %load = call <vscale x 2 x half> @llvm.masked.load.nxv2f16(<vscale x 2 x half> *%a, i32 2, <vscale x 2 x i1> %mask, <vscale x 2 x half> undef)
+  ret <vscale x 2 x half> %load
+}
+
+define <vscale x 4 x float> @masked_load_nxv4f32(<vscale x 4 x float> *%a, <vscale x 4 x i1> %mask) {
+; CHECK-LABEL: masked_load_nxv4f32:
+; CHECK: ld1w { [[IN:z[0-9]+]].s }, [[PG:p[0-9]+]]/z, [x0]
+  %load = call <vscale x 4 x float> @llvm.masked.load.nxv4f32(<vscale x 4 x float> *%a, i32 4, <vscale x 4 x i1> %mask, <vscale x 4 x float> undef)
+  ret <vscale x 4 x float> %load
+}
+
+define <vscale x 4 x half> @masked_load_nxv4f16(<vscale x 4 x half> *%a, <vscale x 4 x i1> %mask) {
+; CHECK-LABEL: masked_load_nxv4f16:
+; CHECK: ld1h { [[IN:z[0-9]+]].s }, [[PG:p[0-9]+]]/z, [x0]
+  %load = call <vscale x 4 x half> @llvm.masked.load.nxv4f16(<vscale x 4 x half> *%a, i32 2, <vscale x 4 x i1> %mask, <vscale x 4 x half> undef)
+  ret <vscale x 4 x half> %load
+}
+
+define <vscale x 8 x half> @masked_load_nxv8f16(<vscale x 8 x half> *%a, <vscale x 8 x i1> %mask) {
+; CHECK-LABEL: masked_load_nxv8f16:
+; CHECK: ld1h { [[IN:z[0-9]+]].h }, [[PG:p[0-9]+]]/z, [x0]
+  %load = call <vscale x 8 x half> @llvm.masked.load.nxv8f16(<vscale x 8 x half> *%a, i32 2, <vscale x 8 x i1> %mask, <vscale x 8 x half> undef)
+  ret <vscale x 8 x half> %load
+}
+
+declare <vscale x 2 x i64> @llvm.masked.load.nxv2i64(<vscale x 2 x i64>*, i32, <vscale x 2 x i1>, <vscale x 2 x i64>)
+declare <vscale x 4 x i32> @llvm.masked.load.nxv4i32(<vscale x 4 x i32>*, i32, <vscale x 4 x i1>, <vscale x 4 x i32>)
+declare <vscale x 8 x i16> @llvm.masked.load.nxv8i16(<vscale x 8 x i16>*, i32, <vscale x 8 x i1>, <vscale x 8 x i16>)
+declare <vscale x 16 x i8> @llvm.masked.load.nxv16i8(<vscale x 16 x i8>*, i32, <vscale x 16 x i1>, <vscale x 16 x i8>)
+
+declare <vscale x 2 x double> @llvm.masked.load.nxv2f64(<vscale x 2 x double>*, i32, <vscale x 2 x i1>, <vscale x 2 x double>)
+declare <vscale x 2 x float> @llvm.masked.load.nxv2f32(<vscale x 2 x float>*, i32, <vscale x 2 x i1>, <vscale x 2 x float>)
+declare <vscale x 2 x half> @llvm.masked.load.nxv2f16(<vscale x 2 x half>*, i32, <vscale x 2 x i1>, <vscale x 2 x half>)
+declare <vscale x 4 x float> @llvm.masked.load.nxv4f32(<vscale x 4 x float>*, i32, <vscale x 4 x i1>, <vscale x 4 x float>)
+declare <vscale x 4 x half> @llvm.masked.load.nxv4f16(<vscale x 4 x half>*, i32, <vscale x 4 x i1>, <vscale x 4 x half>)
+declare <vscale x 8 x half> @llvm.masked.load.nxv8f16(<vscale x 8 x half>*, i32, <vscale x 8 x i1>, <vscale x 8 x half>)

llvm/test/CodeGen/AArch64/sve-masked-ldst-sext.ll

+; RUN: llc -mtriple=aarch64--linux-gnu -mattr=+sve < %s | FileCheck %s
+
+;
+; Masked Loads
+;
+
+define <vscale x 2 x i64> @masked_sload_nxv2i8(<vscale x 2 x i8> *%a, <vscale x 2 x i1> %mask) {
+; CHECK-LABEL: masked_sload_nxv2i8:
+; CHECK: ld1sb { [[IN:z[0-9]+]].d }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 2 x i8> @llvm.masked.load.nxv2i8(<vscale x 2 x i8> *%a, i32 1, <vscale x 2 x i1> %mask, <vscale x 2 x i8> undef)
+  %ext = sext <vscale x 2 x i8> %load to <vscale x 2 x i64>
+  ret <vscale x 2 x i64> %ext
+}
+
+define <vscale x 2 x i64> @masked_sload_nxv2i16(<vscale x 2 x i16> *%a, <vscale x 2 x i1> %mask) {
+; CHECK-LABEL: masked_sload_nxv2i16:
+; CHECK: ld1sh { [[IN:z[0-9]+]].d }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 2 x i16> @llvm.masked.load.nxv2i16(<vscale x 2 x i16> *%a, i32 1, <vscale x 2 x i1> %mask, <vscale x 2 x i16> undef)
+  %ext = sext <vscale x 2 x i16> %load to <vscale x 2 x i64>
+  ret <vscale x 2 x i64> %ext
+}
+
+define <vscale x 2 x i64> @masked_sload_nxv2i32(<vscale x 2 x i32> *%a, <vscale x 2 x i1> %mask) {
+; CHECK-LABEL: masked_sload_nxv2i32:
+; CHECK: ld1sw { [[IN:z[0-9]+]].d }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 2 x i32> @llvm.masked.load.nxv2i32(<vscale x 2 x i32> *%a, i32 1, <vscale x 2 x i1> %mask, <vscale x 2 x i32> undef)
+  %ext = sext <vscale x 2 x i32> %load to <vscale x 2 x i64>
+  ret <vscale x 2 x i64> %ext
+}
+
+define <vscale x 4 x i32> @masked_sload_nxv4i8(<vscale x 4 x i8> *%a, <vscale x 4 x i1> %mask) {
+; CHECK-LABEL: masked_sload_nxv4i8:
+; CHECK: ld1sb { [[IN:z[0-9]+]].s }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 4 x i8> @llvm.masked.load.nxv4i8(<vscale x 4 x i8> *%a, i32 1, <vscale x 4 x i1> %mask, <vscale x 4 x i8> undef)
+  %ext = sext <vscale x 4 x i8> %load to <vscale x 4 x i32>
+  ret <vscale x 4 x i32> %ext
+}
+
+define <vscale x 4 x i32> @masked_sload_nxv4i16(<vscale x 4 x i16> *%a, <vscale x 4 x i1> %mask) {
+; CHECK-LABEL: masked_sload_nxv4i16:
+; CHECK: ld1sh { [[IN:z[0-9]+]].s }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 4 x i16> @llvm.masked.load.nxv4i16(<vscale x 4 x i16> *%a, i32 1, <vscale x 4 x i1> %mask, <vscale x 4 x i16> undef)
+  %ext = sext <vscale x 4 x i16> %load to <vscale x 4 x i32>
+  ret <vscale x 4 x i32> %ext
+}
+
+define <vscale x 8 x i16> @masked_sload_nxv8i8(<vscale x 8 x i8> *%a, <vscale x 8 x i1> %mask) {
+; CHECK-LABEL: masked_sload_nxv8i8:
+; CHECK: ld1sb { [[IN:z[0-9]+]].h }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 8 x i8> @llvm.masked.load.nxv8i8(<vscale x 8 x i8> *%a, i32 1, <vscale x 8 x i1> %mask, <vscale x 8 x i8> undef)
+  %ext = sext <vscale x 8 x i8> %load to <vscale x 8 x i16>
+  ret <vscale x 8 x i16> %ext
+}
+
+declare <vscale x 2 x i8> @llvm.masked.load.nxv2i8(<vscale x 2 x i8>*, i32, <vscale x 2 x i1>, <vscale x 2 x i8>)
+declare <vscale x 2 x i16> @llvm.masked.load.nxv2i16(<vscale x 2 x i16>*, i32, <vscale x 2 x i1>, <vscale x 2 x i16>)
+declare <vscale x 2 x i32> @llvm.masked.load.nxv2i32(<vscale x 2 x i32>*, i32, <vscale x 2 x i1>, <vscale x 2 x i32>)
+declare <vscale x 4 x i8> @llvm.masked.load.nxv4i8(<vscale x 4 x i8>*, i32, <vscale x 4 x i1>, <vscale x 4 x i8>)
+declare <vscale x 4 x i16> @llvm.masked.load.nxv4i16(<vscale x 4 x i16>*, i32, <vscale x 4 x i1>, <vscale x 4 x i16>)
+declare <vscale x 8 x i8> @llvm.masked.load.nxv8i8(<vscale x 8 x i8>*, i32, <vscale x 8 x i1>, <vscale x 8 x i8>)

llvm/test/CodeGen/AArch64/sve-masked-ldst-zext.ll

+; RUN: llc -mtriple=aarch64--linux-gnu -mattr=+sve < %s | FileCheck %s
+
+;
+; Masked Loads
+;
+
+define <vscale x 2 x i64> @masked_zload_nxv2i8(<vscale x 2 x i8>* %src, <vscale x 2 x i1> %mask) {
+; CHECK-LABEL: masked_zload_nxv2i8:
+; CHECK-NOT: ld1sb
+; CHECK: ld1b { [[IN:z[0-9]+]].d }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 2 x i8> @llvm.masked.load.nxv2i8(<vscale x 2 x i8>* %src, i32 1, <vscale x 2 x i1> %mask, <vscale x 2 x i8> undef)
+  %ext = zext <vscale x 2 x i8> %load to <vscale x 2 x i64>
+  ret <vscale x 2 x i64> %ext
+}
+
+define <vscale x 2 x i64> @masked_zload_nxv2i16(<vscale x 2 x i16>* %src, <vscale x 2 x i1> %mask) {
+; CHECK-LABEL: masked_zload_nxv2i16:
+; CHECK-NOT: ld1sh
+; CHECK: ld1h { [[IN:z[0-9]+]].d }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 2 x i16> @llvm.masked.load.nxv2i16(<vscale x 2 x i16>* %src, i32 1, <vscale x 2 x i1> %mask, <vscale x 2 x i16> undef)
+  %ext = zext <vscale x 2 x i16> %load to <vscale x 2 x i64>
+  ret <vscale x 2 x i64> %ext
+}
+
+define <vscale x 2 x i64> @masked_zload_nxv2i32(<vscale x 2 x i32>* %src, <vscale x 2 x i1> %mask) {
+; CHECK-LABEL: masked_zload_nxv2i32:
+; CHECK-NOT: ld1sw
+; CHECK: ld1w { [[IN:z[0-9]+]].d }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 2 x i32> @llvm.masked.load.nxv2i32(<vscale x 2 x i32>* %src, i32 1, <vscale x 2 x i1> %mask, <vscale x 2 x i32> undef)
+  %ext = zext <vscale x 2 x i32> %load to <vscale x 2 x i64>
+  ret <vscale x 2 x i64> %ext
+}
+
+define <vscale x 4 x i32> @masked_zload_nxv4i8(<vscale x 4 x i8>* %src, <vscale x 4 x i1> %mask) {
+; CHECK-LABEL: masked_zload_nxv4i8:
+; CHECK-NOT: ld1sb
+; CHECK: ld1b { [[IN:z[0-9]+]].s }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 4 x i8> @llvm.masked.load.nxv4i8(<vscale x 4 x i8>* %src, i32 1, <vscale x 4 x i1> %mask, <vscale x 4 x i8> undef)
+  %ext = zext <vscale x 4 x i8> %load to <vscale x 4 x i32>
+  ret <vscale x 4 x i32> %ext
+}
+
+define <vscale x 4 x i32> @masked_zload_nxv4i16(<vscale x 4 x i16>* %src, <vscale x 4 x i1> %mask) {
+; CHECK-LABEL: masked_zload_nxv4i16:
+; CHECK-NOT: ld1sh
+; CHECK: ld1h { [[IN:z[0-9]+]].s }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 4 x i16> @llvm.masked.load.nxv4i16(<vscale x 4 x i16>* %src, i32 1, <vscale x 4 x i1> %mask, <vscale x 4 x i16> undef)
+  %ext = zext <vscale x 4 x i16> %load to <vscale x 4 x i32>
+  ret <vscale x 4 x i32> %ext
+}
+
+define <vscale x 8 x i16> @masked_zload_nxv8i8(<vscale x 8 x i8>* %src, <vscale x 8 x i1> %mask) {
+; CHECK-LABEL: masked_zload_nxv8i8:
+; CHECK-NOT: ld1sb
+; CHECK: ld1b { [[IN:z[0-9]+]].h }, [[PG:p[0-9]+]]/z, [x0]
+; CHECK-NEXT: ret
+  %load = call <vscale x 8 x i8> @llvm.masked.load.nxv8i8(<vscale x 8 x i8>* %src, i32 1, <vscale x 8 x i1> %mask, <vscale x 8 x i8> undef)
+  %ext = zext <vscale x 8 x i8> %load to <vscale x 8 x i16>
+  ret <vscale x 8 x i16> %ext
+}
+
+declare <vscale x 2 x i8> @llvm.masked.load.nxv2i8(<vscale x 2 x i8>*, i32, <vscale x 2 x i1>, <vscale x 2 x i8>)
+declare <vscale x 2 x i16> @llvm.masked.load.nxv2i16(<vscale x 2 x i16>*, i32, <vscale x 2 x i1>, <vscale x 2 x i16>)
+declare <vscale x 2 x i32> @llvm.masked.load.nxv2i32(<vscale x 2 x i32>*, i32, <vscale x 2 x i1>, <vscale x 2 x i32>)
+declare <vscale x 4 x i8> @llvm.masked.load.nxv4i8(<vscale x 4 x i8>*, i32, <vscale x 4 x i1>, <vscale x 4 x i8>)
+declare <vscale x 4 x i16> @llvm.masked.load.nxv4i16(<vscale x 4 x i16>*, i32, <vscale x 4 x i1>, <vscale x 4 x i16>)
+declare <vscale x 8 x i8> @llvm.masked.load.nxv8i8(<vscale x 8 x i8>*, i32, <vscale x 8 x i1>, <vscale x 8 x i8>)