[globalisel][tablegen] Import ComplexPattern when used as an operator

[dsanders]

Summary

It's possible for a ComplexPattern to be used as an operator in a match
pattern. This is used by the load/store patterns in AArch64 to name the
suboperands returned by ComplexPattern predicate so that they can be broken
apart and referenced independently in the result pattern.

This patch adds support for this in order to enable the import of load/store
patterns.

Depends on D37445

[dsanders]

Rebase and ping

[qcolombet]

Looks fine with one comment:
Do you think we need a new opcode in the state machine for that?

We could have reused ComplexRender with an additional parameter and use -1 to mean render all of them.
For the sake of optimization, the current patch is actually better, but in terms of simplicity I wonder.

Feel free to commit as is. That was just my 2c :).

[dsanders]

In D37456#896215, @qcolombet wrote:

Looks fine with one comment:
Do you think we need a new opcode in the state machine for that?

We could have reused ComplexRender with an additional parameter and use -1 to mean render all of them.
For the sake of optimization, the current patch is actually better, but in terms of simplicity I wonder.

Feel free to commit as is. That was just my 2c :).

At the moment, I'm leaning towards separate opcodes on the basis that the we shouldn't make the common case longer to account for the rare case. However, the trade-off will be harder once we start trying to compress the table. Right now, opcodes are cheap since we have 2^32 of them but they'll be more valuable if we only have 2^8.

I think we should note this down as something to evaluate when we compress the table.

include/llvm/CodeGen/GlobalISel/InstructionSelector.h

 /// It's implemented by the target. It's used by the InstructionSelect pass.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CODEGEN_GLOBALISEL_INSTRUCTIONSELECTOR_H
 #define LLVM_CODEGEN_GLOBALISEL_INSTRUCTIONSELECTOR_H
 
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Optional.h"
 #include <bitset>
 #include <cstddef>
 #include <cstdint>
 #include <functional>
 #include <initializer_list>
 #include <vector>
 
 namespace llvm {
enum {
   /// Add an immediate to the specified instruction
   /// - InsnID - Instruction ID to modify
   /// - Imm - The immediate to add
   GIR_AddImm,
   /// Render complex operands to the specified instruction
   /// - InsnID - Instruction ID to modify
   /// - RendererID - The renderer to call
   GIR_ComplexRenderer,
+  /// Render sub-operands of complex operands to the specified instruction
+  /// - InsnID - Instruction ID to modify
+  /// - RendererID - The renderer to call
+  /// - RenderOpID - The suboperand to render.
+  GIR_ComplexSubOperandRenderer,
 
   /// Render a G_CONSTANT operator as a sign-extended immediate.
   /// - NewInsnID - Instruction ID to modify
   /// - OldInsnID - Instruction ID to copy from
   /// The operand index is implicitly 1.
   GIR_CopyConstantAsSImm,
 
   /// Constrain an instruction operand to a register class.
public:
   /// \post
   ///   if returns true:
   ///     for I in all mutated/inserted instructions:
   ///       !isPreISelGenericOpcode(I.getOpcode())
   ///
   virtual bool select(MachineInstr &I) const = 0;
 
 protected:
-  using ComplexRendererFn = std::function<void(MachineInstrBuilder &)>;
+  using ComplexRendererFn =
+      Optional<SmallVector<std::function<void(MachineInstrBuilder &)>, 4>>;
   using RecordedMIVector = SmallVector<MachineInstr *, 4>;
   using NewMIVector = SmallVector<MachineInstrBuilder, 4>;
 
   struct MatcherState {
-    std::vector<ComplexRendererFn> Renderers;
+    std::vector<ComplexRendererFn::value_type> Renderers;
     RecordedMIVector MIs;
 
     MatcherState(unsigned MaxRenderers);
   };
 
 public:
   template <class PredicateBitset, class ComplexMatcherMemFn>
   struct MatcherInfoTy {

include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h

case GIM_CheckComplexPattern: {
       int64_t RendererID = MatchTable[CurrentIdx++];
       int64_t ComplexPredicateID = MatchTable[CurrentIdx++];
       DEBUG(dbgs() << CurrentIdx << ": State.Renderers[" << RendererID
                    << "] = GIM_CheckComplexPattern(MIs[" << InsnID
                    << "]->getOperand(" << OpIdx
                    << "), ComplexPredicateID=" << ComplexPredicateID << ")\n");
       assert(State.MIs[InsnID] != nullptr && "Used insn before defined");
       // FIXME: Use std::invoke() when it's available.
-      if (!(State.Renderers[RendererID] =
-                (ISel.*MatcherInfo.ComplexPredicates[ComplexPredicateID])(
-                    State.MIs[InsnID]->getOperand(OpIdx)))) {
+      ComplexRendererFn Renderer =
+              State.MIs[InsnID]->getOperand(OpIdx));
+      if (Renderer.hasValue())
+        State.Renderers[RendererID] = Renderer.getValue();
+      else
         if (handleReject() == RejectAndGiveUp)
           return false;
-      }
       break;
     }
     case GIM_CheckConstantInt: {
       int64_t InsnID = MatchTable[CurrentIdx++];
       int64_t OpIdx = MatchTable[CurrentIdx++];
       int64_t Value = MatchTable[CurrentIdx++];
       DEBUG(dbgs() << CurrentIdx << ": GIM_CheckConstantInt(MIs[" << InsnID
                    << "]->getOperand(" << OpIdx << "), Value=" << Value
case GIR_AddImm: {
       DEBUG(dbgs() << CurrentIdx << ": GIR_AddImm(OutMIs[" << InsnID << "], "
                    << Imm << ")\n");
       break;
     }
     case GIR_ComplexRenderer: {
       int64_t InsnID = MatchTable[CurrentIdx++];
       int64_t RendererID = MatchTable[CurrentIdx++];
       assert(OutMIs[InsnID] && "Attempted to add to undefined instruction");
-      State.Renderers[RendererID](OutMIs[InsnID]);
+      for (const auto &RenderOpFn : State.Renderers[RendererID])
+        RenderOpFn(OutMIs[InsnID]);
       DEBUG(dbgs() << CurrentIdx << ": GIR_ComplexRenderer(OutMIs[" << InsnID
                    << "], " << RendererID << ")\n");
       break;
     }
+    case GIR_ComplexSubOperandRenderer: {
+      int64_t InsnID = MatchTable[CurrentIdx++];
+      int64_t RendererID = MatchTable[CurrentIdx++];
+      int64_t RenderOpID = MatchTable[CurrentIdx++];
+      assert(OutMIs[InsnID] && "Attempted to add to undefined instruction");
+      State.Renderers[RendererID][RenderOpID](OutMIs[InsnID]);
+      DEBUG(dbgs() << CurrentIdx << ": GIR_ComplexSubOperandRenderer(OutMIs["
+                   << InsnID << "], " << RendererID << ", " << RenderOpID
+                   << ")\n");
+      break;
+    }
 
     case GIR_CopyConstantAsSImm: {
       int64_t NewInsnID = MatchTable[CurrentIdx++];
       int64_t OldInsnID = MatchTable[CurrentIdx++];
       assert(OutMIs[NewInsnID] && "Attempted to add to undefined instruction");
       assert(State.MIs[OldInsnID]->getOpcode() == TargetOpcode::G_CONSTANT && "Expected G_CONSTANT");
       if (State.MIs[OldInsnID]->getOperand(1).isCImm()) {
         OutMIs[NewInsnID].addImm(

lib/CodeGen/GlobalISel/InstructionSelector.cpp

 #include "llvm/Target/TargetRegisterInfo.h"
 #include <cassert>
 
 #define DEBUG_TYPE "instructionselector"
 
 using namespace llvm;
 
 InstructionSelector::MatcherState::MatcherState(unsigned MaxRenderers)
-    : Renderers(MaxRenderers, nullptr), MIs() {}
+    : Renderers(MaxRenderers, {}), MIs() {}
 
 InstructionSelector::InstructionSelector() = default;
 
 bool InstructionSelector::constrainOperandRegToRegClass(
     MachineInstr &I, unsigned OpIdx, const TargetRegisterClass &RC,
     const TargetInstrInfo &TII, const TargetRegisterInfo &TRI,
     const RegisterBankInfo &RBI) const {
   MachineBasicBlock &MBB = *I.getParent();

lib/Target/AArch64/AArch64InstructionSelector.cpp

AArch64InstructionSelector::selectArithImmed(MachineOperand &Root) const {
   uint64_t Immed;
   if (Root.isImm())
     Immed = Root.getImm();
   else if (Root.isCImm())
     Immed = Root.getCImm()->getZExtValue();
   else if (Root.isReg()) {
     MachineInstr *Def = MRI.getVRegDef(Root.getReg());
     if (Def->getOpcode() != TargetOpcode::G_CONSTANT)
-      return nullptr;
+      return None;
     MachineOperand &Op1 = Def->getOperand(1);
     if (!Op1.isCImm() || Op1.getCImm()->getBitWidth() > 64)
-      return nullptr;
+      return None;
     Immed = Op1.getCImm()->getZExtValue();
   } else
-    return nullptr;
+    return None;
 
   unsigned ShiftAmt;
 
   if (Immed >> 12 == 0) {
     ShiftAmt = 0;
   } else if ((Immed & 0xfff) == 0 && Immed >> 24 == 0) {
     ShiftAmt = 12;
     Immed = Immed >> 12;
   } else
-    return nullptr;
+    return None;
 
   unsigned ShVal = AArch64_AM::getShifterImm(AArch64_AM::LSL, ShiftAmt);
-  return [=](MachineInstrBuilder &MIB) { MIB.addImm(Immed).addImm(ShVal); };
+  return {{
+      [=](MachineInstrBuilder &MIB) { MIB.addImm(Immed); },
+      [=](MachineInstrBuilder &MIB) { MIB.addImm(ShVal); },
+  }};
 }
 
 namespace llvm {
 InstructionSelector *
 createAArch64InstructionSelector(const AArch64TargetMachine &TM,
                                  AArch64Subtarget &Subtarget,
                                  AArch64RegisterBankInfo &RBI) {
   return new AArch64InstructionSelector(TM, Subtarget, RBI);
 }
 }

test/TableGen/GlobalISelEmitter.td

 }
 
 def complex : Operand<i32>, ComplexPattern<i32, 2, "SelectComplexPattern", []> {
   let MIOperandInfo = (ops i32imm, i32imm);
 }
 def gi_complex :
     GIComplexOperandMatcher<s32, "selectComplexPattern">,
     GIComplexPatternEquiv<complex>;
+def complex_rr : Operand<i32>, ComplexPattern<i32, 2, "SelectComplexPatternRR", []> {
+  let MIOperandInfo = (ops GPR32, GPR32);
+}
+def gi_complex_rr :
+    GIComplexOperandMatcher<s32, "selectComplexPatternRR">,
+    GIComplexPatternEquiv<complex_rr>;
 
 def m1 : OperandWithDefaultOps <i32, (ops (i32 -1))>;
 def Z : OperandWithDefaultOps <i32, (ops R0)>;
 def m1Z : OperandWithDefaultOps <i32, (ops (i32 -1), R0)>;
 
 def HasA : Predicate<"Subtarget->hasA()">;
 def HasB : Predicate<"Subtarget->hasB()">;
 def HasC : Predicate<"Subtarget->hasC()"> { let RecomputePerFunction = 1; }

 // CHECK-NEXT:    const MatcherInfoTy<PredicateBitset, ComplexMatcherMemFn> MatcherInfo;
 // CHECK-NEXT:  #endif // ifdef GET_GLOBALISEL_TEMPORARIES_DECL
 
 // CHECK-LABEL: #ifdef GET_GLOBALISEL_TEMPORARIES_INIT
 // CHECK-NEXT:    , State(2),
 // CHECK-NEXT:    MatcherInfo({TypeObjects, FeatureBitsets, I64ImmPredicateFns, APIntImmPredicateFns, APFloatImmPredicateFns, {
 // CHECK-NEXT:      nullptr, // GICP_Invalid
 // CHECK-NEXT:      &MyTargetInstructionSelector::selectComplexPattern, // gi_complex
+// CHECK-NEXT:      &MyTargetInstructionSelector::selectComplexPatternRR, // gi_complex_rr
 // CHECK-NEXT:    }})
 // CHECK-NEXT:  #endif // ifdef GET_GLOBALISEL_TEMPORARIES_INIT
 
 // CHECK-LABEL: enum SubtargetFeatureBits : uint8_t {
 // CHECK-NEXT:    Feature_HasABit = 0,
 // CHECK-NEXT:    Feature_HasBBit = 1,
 // CHECK-NEXT:    Feature_HasCBit = 2,
 // CHECK-NEXT:  };

 // CHECK-NEXT:    {Feature_HasABit, },
 // CHECK-NEXT:    {Feature_HasABit, Feature_HasBBit, Feature_HasCBit, },
 // CHECK-NEXT:  };
 
 // CHECK-LABEL: // ComplexPattern predicates.
 // CHECK-NEXT:  enum {
 // CHECK-NEXT:    GICP_Invalid,
 // CHECK-NEXT:    GICP_gi_complex,
+// CHECK-NEXT:    GICP_gi_complex_rr,
 // CHECK-NEXT:  };
 
 // CHECK-LABEL: // PatFrag predicates.
 // CHECK-NEXT:  enum {
 // CHECK-NEXT:    GIPFP_I64_Predicate_simm8 = GIPFP_I64_Invalid + 1,
 // CHECK-NEXT:  };
 // CHECK-NEXT:  static bool Predicate_simm8(int64_t Imm) { return isInt<8>(Imm);   }
 // CHECK-NEXT:  static InstructionSelector::I64ImmediatePredicateFn I64ImmPredicateFns[] = {

 // CHECK-NEXT:    GIR_ComplexRenderer, /*InsnID*/0, /*RendererID*/0,
 // CHECK-NEXT:    GIR_MergeMemOperands, /*InsnID*/0, /*MergeInsnID's*/0, GIU_MergeMemOperands_EndOfList,
 // CHECK-NEXT:    GIR_EraseFromParent, /*InsnID*/0,
 // CHECK-NEXT:    GIR_ConstrainSelectedInstOperands, /*InsnID*/0,
 // CHECK-NEXT:    GIR_Done,
 // CHECK-NEXT:  // Label 0: @[[LABEL]]
 
 def INSN3 : I<(outs GPR32:$dst),
-              (ins GPR32Op:$src1, complex:$src2, GPR32:$src3, complex:$src4, complex:$src5), []>;
-def : Pat<(select GPR32:$src1, complex:$src2, (select GPR32:$src3, complex:$src4, complex:$src5)),
-          (INSN3 GPR32:$src1, complex:$src2, GPR32:$src3, complex:$src4, complex:$src5)>;
+              (ins GPR32Op:$src1, GPR32:$src2a, GPR32:$src2b, GPR32:$src3, complex:$src4, i32imm:$src5a, i32imm:$src5b), []>;
+def : Pat<(select GPR32:$src1, (complex_rr GPR32:$src2a, GPR32:$src2b),
+                               (select GPR32:$src3,
+                                       complex:$src4,
+                                       (complex i32imm:$src5a, i32imm:$src5b))),
+          (INSN3 GPR32:$src1, GPR32:$src2b, GPR32:$src2a, GPR32:$src3,
+                 complex:$src4, i32imm:$src5a, i32imm:$src5b)>;
 
 //===- Test a pattern with multiple ComplexPattern operands. --------------===//
 //
 
 // CHECK-NEXT:  GIM_Try, /*On fail goto*//*Label 1*/ [[LABEL:[0-9]+]],
 // CHECK-NEXT:    GIM_CheckNumOperands, /*MI*/0, /*Expected*/4,
 // CHECK-NEXT:    GIM_RecordInsn, /*DefineMI*/1, /*MI*/0, /*OpIdx*/3, // MIs[1]
 // CHECK-NEXT:    GIM_CheckNumOperands, /*MI*/1, /*Expected*/4,
 // CHECK-NEXT:    GIM_CheckOpcode, /*MI*/0, TargetOpcode::G_SELECT,
 // CHECK-NEXT:    // MIs[0] dst
 // CHECK-NEXT:    GIM_CheckType, /*MI*/0, /*Op*/0, /*Type*/GILLT_s32,
 // CHECK-NEXT:    GIM_CheckRegBankForClass, /*MI*/0, /*Op*/0, /*RC*/MyTarget::GPR32RegClassID,
 // CHECK-NEXT:    // MIs[0] src1
 // CHECK-NEXT:    GIM_CheckType, /*MI*/0, /*Op*/1, /*Type*/GILLT_s32,
 // CHECK-NEXT:    GIM_CheckRegBankForClass, /*MI*/0, /*Op*/1, /*RC*/MyTarget::GPR32RegClassID,
-// CHECK-NEXT:    // MIs[0] src2
+// CHECK-NEXT:    // MIs[0] Operand 2
 // CHECK-NEXT:    GIM_CheckType, /*MI*/0, /*Op*/2, /*Type*/GILLT_s32,
-// CHECK-NEXT:    GIM_CheckComplexPattern, /*MI*/0, /*Op*/2, /*Renderer*/0, GICP_gi_complex,
+// CHECK-NEXT:    GIM_CheckComplexPattern, /*MI*/0, /*Op*/2, /*Renderer*/0, GICP_gi_complex_rr,
 // CHECK-NEXT:    // MIs[0] Operand 3
 // CHECK-NEXT:    GIM_CheckType, /*MI*/0, /*Op*/3, /*Type*/GILLT_s32,
 // CHECK-NEXT:    GIM_CheckOpcode, /*MI*/1, TargetOpcode::G_SELECT,
 // CHECK-NEXT:    // MIs[1] Operand 0
 // CHECK-NEXT:    GIM_CheckType, /*MI*/1, /*Op*/0, /*Type*/GILLT_s32,
 // CHECK-NEXT:    // MIs[1] src3
 // CHECK-NEXT:    GIM_CheckType, /*MI*/1, /*Op*/1, /*Type*/GILLT_s32,
 // CHECK-NEXT:    GIM_CheckRegBankForClass, /*MI*/1, /*Op*/1, /*RC*/MyTarget::GPR32RegClassID,
 // CHECK-NEXT:    // MIs[1] src4
 // CHECK-NEXT:    GIM_CheckType, /*MI*/1, /*Op*/2, /*Type*/GILLT_s32,
 // CHECK-NEXT:    GIM_CheckComplexPattern, /*MI*/1, /*Op*/2, /*Renderer*/1, GICP_gi_complex,
-// CHECK-NEXT:    // MIs[1] src5
+// CHECK-NEXT:    // MIs[1] Operand 3
 // CHECK-NEXT:    GIM_CheckType, /*MI*/1, /*Op*/3, /*Type*/GILLT_s32,
 // CHECK-NEXT:    GIM_CheckComplexPattern, /*MI*/1, /*Op*/3, /*Renderer*/2, GICP_gi_complex,
 // CHECK-NEXT:    GIM_CheckIsSafeToFold, /*InsnID*/1,
-// CHECK-NEXT:    // (select:i32 GPR32:i32:$src1, complex:i32:$src2, (select:i32 GPR32:i32:$src3, complex:i32:$src4, complex:i32:$src5))  =>  (INSN3:i32 GPR32:i32:$src1, complex:i32:$src2, GPR32:i32:$src3, complex:i32:$src4, complex:i32:$src5)
+// CHECK-NEXT:    // (select:i32 GPR32:i32:$src1, (complex_rr:i32 GPR32:i32:$src2a, GPR32:i32:$src2b), (select:i32 GPR32:i32:$src3, complex:i32:$src4, (complex:i32 i32imm:i32:$src5a, i32imm:i32:$src5b)))  =>  (INSN3:i32 GPR32:i32:$src1, GPR32:i32:$src2b, GPR32:i32:$src2a, GPR32:i32:$src3, complex:i32:$src4, i32imm:i32:$src5a, i32imm:i32:$src5b)
 // CHECK-NEXT:    GIR_BuildMI, /*InsnID*/0, /*Opcode*/MyTarget::INSN3,
 // CHECK-NEXT:    GIR_Copy, /*NewInsnID*/0, /*OldInsnID*/0, /*OpIdx*/0, // dst
 // CHECK-NEXT:    GIR_Copy, /*NewInsnID*/0, /*OldInsnID*/0, /*OpIdx*/1, // src1
-// CHECK-NEXT:    GIR_ComplexRenderer, /*InsnID*/0, /*RendererID*/0,
+// CHECK-NEXT:    GIR_ComplexSubOperandRenderer, /*InsnID*/0, /*RendererID*/0, /*SubOperand*/1, // src2b
+// CHECK-NEXT:    GIR_ComplexSubOperandRenderer, /*InsnID*/0, /*RendererID*/0, /*SubOperand*/0, // src2a
 // CHECK-NEXT:    GIR_Copy, /*NewInsnID*/0, /*OldInsnID*/1, /*OpIdx*/1, // src3
 // CHECK-NEXT:    GIR_ComplexRenderer, /*InsnID*/0, /*RendererID*/1,
-// CHECK-NEXT:    GIR_ComplexRenderer, /*InsnID*/0, /*RendererID*/2,
+// CHECK-NEXT:    GIR_ComplexSubOperandRenderer, /*InsnID*/0, /*RendererID*/2, /*SubOperand*/0, // src5a
+// CHECK-NEXT:    GIR_ComplexSubOperandRenderer, /*InsnID*/0, /*RendererID*/2, /*SubOperand*/1, // src5b
 // CHECK-NEXT:    GIR_EraseFromParent, /*InsnID*/0,
 // CHECK-NEXT:    GIR_ConstrainSelectedInstOperands, /*InsnID*/0,
 // CHECK-NEXT:    GIR_Done,
 // CHECK-NEXT:  // Label 1: @[[LABEL]]
 
 def : GINodeEquiv<G_SELECT, select>;
 let mayLoad = 1 in {
   def INSN2 : I<(outs GPR32:$dst), (ins GPR32Op:$src1, complex:$src2, complex:$src3), []>;

utils/TableGen/GlobalISelEmitter.cpp

 
 std::string explainOperator(Record *Operator) {
   if (Operator->isSubClassOf("SDNode"))
     return (" (" + Operator->getValueAsString("Opcode") + ")").str();
 
   if (Operator->isSubClassOf("Intrinsic"))
     return (" (Operator is an Intrinsic, " + Operator->getName() + ")").str();
 
-  return " (Operator not understood)";
+  if (Operator->isSubClassOf("ComplexPattern"))
+    return (" (Operator is an unmapped ComplexPattern, " + Operator->getName() +
+            ")")
+        .str();
+
+  return (" (Operator " + Operator->getName() + " not understood)").str();
 }
 
 /// Helper function to let the emitter report skip reason error messages.
 static Error failedImport(const Twine &Reason) {
   return make_error<StringError>(Reason, inconvertibleErrorCode());
 }
 
 static Error isTrivialOperatorNode(const TreePatternNode *N) {
class RuleMatcher {
 
   /// ID for the next instruction variable defined with defineInsnVar()
   unsigned NextInsnVarID;
 
   std::vector<Record *> RequiredFeatures;
 
   ArrayRef<SMLoc> SrcLoc;
 
+  typedef std::tuple<Record *, unsigned, unsigned>
+      DefinedComplexPatternSubOperand;
+  typedef StringMap<DefinedComplexPatternSubOperand>
+      DefinedComplexPatternSubOperandMap;
+  /// A map of Symbolic Names to ComplexPattern sub-operands.
+  DefinedComplexPatternSubOperandMap ComplexSubOperands;
+
 public:
   RuleMatcher(ArrayRef<SMLoc> SrcLoc)
       : Matchers(), Actions(), InsnVariableIDs(), DefinedOperands(),
-        NextInsnVarID(0), SrcLoc(SrcLoc) {}
+        NextInsnVarID(0), SrcLoc(SrcLoc), ComplexSubOperands() {}
   RuleMatcher(RuleMatcher &&Other) = default;
   RuleMatcher &operator=(RuleMatcher &&Other) = default;
 
   InstructionMatcher &addInstructionMatcher(StringRef SymbolicName);
   void addRequiredFeature(Record *Feature);
   const std::vector<Record *> &getRequiredFeatures() const;
 
   template <class Kind, class... Args> Kind &addAction(Args &&... args);
public:
   }
   iterator_range<typename DefinedInsnVariablesMap::const_iterator>
   defined_insn_vars() const {
     return make_range(defined_insn_vars_begin(), defined_insn_vars_end());
   }
 
   void defineOperand(StringRef SymbolicName, OperandMatcher &OM);
 
+  void defineComplexSubOperand(StringRef SymbolicName, Record *ComplexPattern,
+                               unsigned RendererID, unsigned SubOperandID) {
+    assert(ComplexSubOperands.count(SymbolicName) == 0 && "Already defined");
+    ComplexSubOperands[SymbolicName] =
+        std::make_tuple(ComplexPattern, RendererID, SubOperandID);
+  }
+  Optional<DefinedComplexPatternSubOperand>
+  getComplexSubOperand(StringRef SymbolicName) const {
+    const auto &I = ComplexSubOperands.find(SymbolicName);
+    if (I == ComplexSubOperands.end())
+      return None;
+    return I->second;
+  }
+
   const InstructionMatcher &getInstructionMatcher(StringRef SymbolicName) const;
   const OperandMatcher &getOperandMatcher(StringRef Name) const;
 
   void emitCaptureOpcodes(MatchTable &Table);
 
   void emit(MatchTable &Table);
 
   /// Compare the priority of this object and B.

 private:
   unsigned InsnID;
   const Record &TheDef;
   /// The name of the operand.
   const StringRef SymbolicName;
   /// The renderer number. This must be unique within a rule since it's used to
   /// identify a temporary variable to hold the renderer function.
   unsigned RendererID;
+  /// When provided, this is the suboperand of the ComplexPattern operand to
+  /// render. Otherwise all the suboperands will be rendered.
+  Optional<unsigned> SubOperand;
 
   unsigned getNumOperands() const {
     return TheDef.getValueAsDag("Operands")->getNumArgs();
   }
 
 public:
   RenderComplexPatternOperand(unsigned InsnID, const Record &TheDef,
-                              StringRef SymbolicName, unsigned RendererID)
+                              StringRef SymbolicName, unsigned RendererID,
+                              Optional<unsigned> SubOperand = None)
       : OperandRenderer(OR_ComplexPattern), InsnID(InsnID), TheDef(TheDef),
-        SymbolicName(SymbolicName), RendererID(RendererID) {}
+        SymbolicName(SymbolicName), RendererID(RendererID),
+        SubOperand(SubOperand) {}
 
   static bool classof(const OperandRenderer *R) {
     return R->getKind() == OR_ComplexPattern;
   }
 
   void emitRenderOpcodes(MatchTable &Table, RuleMatcher &Rule) const override {
-    Table << MatchTable::Opcode("GIR_ComplexRenderer")
+    Table << MatchTable::Opcode(SubOperand.hasValue() ? "GIR_ComplexSubOperandRenderer"
+                                                      : "GIR_ComplexRenderer")
           << MatchTable::Comment("InsnID") << MatchTable::IntValue(InsnID)
           << MatchTable::Comment("RendererID")
-          << MatchTable::IntValue(RendererID) << MatchTable::LineBreak;
+          << MatchTable::IntValue(RendererID);
+    if (SubOperand.hasValue())
+      Table << MatchTable::Comment("SubOperand")
+            << MatchTable::IntValue(SubOperand.getValue());
+    Table << MatchTable::Comment(SymbolicName) << MatchTable::LineBreak;
   }
 };
 
 /// An action taken when all Matcher predicates succeeded for a parent rule.
 ///
 /// Typical actions include:
 /// * Changing the opcode of an instruction.
 /// * Adding an operand to an instruction.
private:
 
   // Map of predicates to their subtarget features.
   SubtargetFeatureInfoMap SubtargetFeatures;
 
   void gatherNodeEquivs();
   Record *findNodeEquiv(Record *N) const;
 
   Error importRulePredicates(RuleMatcher &M, ArrayRef<Init *> Predicates);
-  Expected<InstructionMatcher &>
-  createAndImportSelDAGMatcher(InstructionMatcher &InsnMatcher,
-                               const TreePatternNode *Src,
+  Expected<InstructionMatcher &> createAndImportSelDAGMatcher(
+      RuleMatcher &Rule, InstructionMatcher &InsnMatcher,
+      const TreePatternNode *Src, unsigned &TempOpIdx) const;
+  Error importComplexPatternOperandMatcher(OperandMatcher &OM, Record *R,
                                            unsigned &TempOpIdx) const;
-  Error importChildMatcher(InstructionMatcher &InsnMatcher,
+  Error importChildMatcher(RuleMatcher &Rule, InstructionMatcher &InsnMatcher,
                            const TreePatternNode *SrcChild, unsigned OpIdx,
                            unsigned &TempOpIdx) const;
   Expected<BuildMIAction &>
   createAndImportInstructionRenderer(RuleMatcher &M, const TreePatternNode *Dst,
                                      const InstructionMatcher &InsnMatcher);
   Error importExplicitUseRenderer(RuleMatcher &Rule,
                                   BuildMIAction &DstMIBuilder,
                                   TreePatternNode *DstChild,
for (const Init *Predicate : Predicates) {
     const DefInit *PredicateDef = static_cast<const DefInit *>(Predicate);
     declareSubtargetFeature(PredicateDef->getDef());
     M.addRequiredFeature(PredicateDef->getDef());
   }
 
   return Error::success();
 }
 
-Expected<InstructionMatcher &>
-GlobalISelEmitter::createAndImportSelDAGMatcher(InstructionMatcher &InsnMatcher,
-                                                const TreePatternNode *Src,
-                                                unsigned &TempOpIdx) const {
+Expected<InstructionMatcher &> GlobalISelEmitter::createAndImportSelDAGMatcher(
+    RuleMatcher &Rule, InstructionMatcher &InsnMatcher,
+    const TreePatternNode *Src, unsigned &TempOpIdx) const {
   Record *SrcGIEquivOrNull = nullptr;
   const CodeGenInstruction *SrcGIOrNull = nullptr;
 
   // Start with the defined operands (i.e., the results of the root operator).
   if (Src->getExtTypes().size() > 1)
     return failedImport("Src pattern has multiple results");
 
   if (Src->isLeaf()) {
for (unsigned i = 0, e = Src->getNumChildren(); i != e; ++i) {
           if (!OM.isTied())
             OM.addPredicate<IntrinsicIDOperandMatcher>(II);
           continue;
         }
 
         return failedImport("Expected IntInit containing instrinsic ID)");
       }
 
-      if (auto Error =
-              importChildMatcher(InsnMatcher, SrcChild, OpIdx++, TempOpIdx))
+      if (auto Error = importChildMatcher(Rule, InsnMatcher, SrcChild, OpIdx++,
+                                          TempOpIdx))
         return std::move(Error);
     }
   }
 
   return InsnMatcher;
 }
 
-Error GlobalISelEmitter::importChildMatcher(InstructionMatcher &InsnMatcher,
+Error GlobalISelEmitter::importComplexPatternOperandMatcher(
+    OperandMatcher &OM, Record *R, unsigned &TempOpIdx) const {
+  const auto &ComplexPattern = ComplexPatternEquivs.find(R);
+  if (ComplexPattern == ComplexPatternEquivs.end())
+    return failedImport("SelectionDAG ComplexPattern (" + R->getName() +
+                        ") not mapped to GlobalISel");
+
+  OM.addPredicate<ComplexPatternOperandMatcher>(OM, *ComplexPattern->second);
+  TempOpIdx++;
+  return Error::success();
+}
+
+Error GlobalISelEmitter::importChildMatcher(RuleMatcher &Rule,
+                                            InstructionMatcher &InsnMatcher,
                                             const TreePatternNode *SrcChild,
                                             unsigned OpIdx,
                                             unsigned &TempOpIdx) const {
   OperandMatcher &OM =
       InsnMatcher.addOperand(OpIdx, SrcChild->getName(), TempOpIdx);
   if (OM.isTied())
     return Error::success();
 
Error GlobalISelEmitter::importChildMatcher(RuleMatcher &Rule,
 
   auto OpTyOrNone = MVTToLLT(ChildTypes.front().getConcrete());
   if (!OpTyOrNone)
     return failedImport("Src operand has an unsupported type (" + to_string(*SrcChild) + ")");
   OM.addPredicate<LLTOperandMatcher>(*OpTyOrNone);
 
   // Check for nested instructions.
   if (!SrcChild->isLeaf()) {
+    if (SrcChild->getOperator()->isSubClassOf("ComplexPattern")) {
+      // When a ComplexPattern is used as an operator, it should do the same
+      // thing as when used as a leaf. However, the children of the operator
+      // name the sub-operands that make up the complex operand and we must
+      // prepare to reference them in the renderer too.
+      unsigned RendererID = TempOpIdx;
+      if (auto Error = importComplexPatternOperandMatcher(
+              OM, SrcChild->getOperator(), TempOpIdx))
+        return Error;
+
+      for (unsigned i = 0, e = SrcChild->getNumChildren(); i != e; ++i) {
+        auto *SubOperand = SrcChild->getChild(i);
+        if (!SubOperand->getName().empty())
+          Rule.defineComplexSubOperand(SubOperand->getName(),
+                                       SrcChild->getOperator(), RendererID, i);
+      }
+
+      return Error::success();
+    }
+
     // Map the node to a gMIR instruction.
     InstructionOperandMatcher &InsnOperand =
         OM.addPredicate<InstructionOperandMatcher>(InsnMatcher.getRuleMatcher(),
                                                    SrcChild->getName());
     auto InsnMatcherOrError = createAndImportSelDAGMatcher(
-        InsnOperand.getInsnMatcher(), SrcChild, TempOpIdx);
+        Rule, InsnOperand.getInsnMatcher(), SrcChild, TempOpIdx);
     if (auto Error = InsnMatcherOrError.takeError())
       return Error;
 
     return Error::success();
   }
 
   // Check for constant immediates.
   if (auto *ChildInt = dyn_cast<IntInit>(SrcChild->getLeafValue())) {
if (auto *ChildDefInit = dyn_cast<DefInit>(SrcChild->getLeafValue())) {
     if (ChildRec->isSubClassOf("RegisterClass") ||
         ChildRec->isSubClassOf("RegisterOperand")) {
       OM.addPredicate<RegisterBankOperandMatcher>(
           Target.getRegisterClass(getInitValueAsRegClass(ChildDefInit)));
       return Error::success();
     }
 
     // Check for ComplexPattern's.
-    if (ChildRec->isSubClassOf("ComplexPattern")) {
-      const auto &ComplexPattern = ComplexPatternEquivs.find(ChildRec);
-      if (ComplexPattern == ComplexPatternEquivs.end())
-        return failedImport("SelectionDAG ComplexPattern (" +
-                            ChildRec->getName() + ") not mapped to GlobalISel");
-
-      OM.addPredicate<ComplexPatternOperandMatcher>(OM,
-                                                    *ComplexPattern->second);
-      TempOpIdx++;
-      return Error::success();
-    }
+    if (ChildRec->isSubClassOf("ComplexPattern"))
+      return importComplexPatternOperandMatcher(OM, ChildRec, TempOpIdx);
 
     if (ChildRec->isSubClassOf("ImmLeaf")) {
       return failedImport(
           "Src pattern child def is an unsupported tablegen class (ImmLeaf)");
     }
 
     return failedImport(
         "Src pattern child def is an unsupported tablegen class");
   }
 
   return failedImport("Src pattern child is an unsupported kind");
 }
 
 Error GlobalISelEmitter::importExplicitUseRenderer(
     RuleMatcher &Rule, BuildMIAction &DstMIBuilder, TreePatternNode *DstChild,
     const InstructionMatcher &InsnMatcher) const {
   if (DstChild->getTransformFn() != nullptr) {
     return failedImport("Dst pattern child has transform fn " +
                         DstChild->getTransformFn()->getName());
   }
 
+  const auto &SubOperand = Rule.getComplexSubOperand(DstChild->getName());
+  if (SubOperand.hasValue()) {
+    DstMIBuilder.addRenderer<RenderComplexPatternOperand>(
+        0, *std::get<0>(*SubOperand), DstChild->getName(),
+        std::get<1>(*SubOperand), std::get<2>(*SubOperand));
+    return Error::success();
+  }
+
   if (!DstChild->isLeaf()) {
     // We accept 'bb' here. It's an operator because BasicBlockSDNode isn't
     // inline, but in MI it's just another operand.
     if (DstChild->getOperator()->isSubClassOf("SDNode")) {
       auto &ChildSDNI = CGP.getSDNodeInfo(DstChild->getOperator());
       if (ChildSDNI.getSDClassName() == "BasicBlockSDNode") {
         DstMIBuilder.addRenderer<CopyRenderer>(0, InsnMatcher,
                                                DstChild->getName());
return failedImport("Dst pattern root isn't a trivial operator (" +
                         toString(std::move(Err)) + ")");
   if (auto Err = isTrivialOperatorNode(Src))
     return failedImport("Src pattern root isn't a trivial operator (" +
                         toString(std::move(Err)) + ")");
 
   InstructionMatcher &InsnMatcherTemp = M.addInstructionMatcher(Src->getName());
   unsigned TempOpIdx = 0;
   auto InsnMatcherOrError =
-      createAndImportSelDAGMatcher(InsnMatcherTemp, Src, TempOpIdx);
+      createAndImportSelDAGMatcher(M, InsnMatcherTemp, Src, TempOpIdx);
   if (auto Error = InsnMatcherOrError.takeError())
     return std::move(Error);
   InstructionMatcher &InsnMatcher = InsnMatcherOrError.get();
 
   if (Dst->isLeaf()) {
     Record *RCDef = getInitValueAsRegClass(Dst->getLeafValue());
 
     const CodeGenRegisterClass &RC = Target.getRegisterClass(RCDef);