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

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

Reviewers: ab, qcolombet, t.p.northover, rovka, aditya_nandakumar

Reviewed By: qcolombet

Subscribers: aemerson, javed.absar, igorb, llvm-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D37456

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315863 91177308-0d34-0410-b5e6-96231b3b80d8

6 files changed, 159 insertions, 53 deletions

diff --git a/include/llvm/CodeGen/GlobalISel/InstructionSelector.h b/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
index 3cc1d35cc5c..d86f02b8ae2 100644
--- a/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
+++ b/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
@@ -17,6 +17,7 @@
 #define LLVM_CODEGEN_GLOBALISEL_INSTRUCTIONSELECTOR_H
 
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Optional.h"
 #include <bitset>
 #include <cstddef>
 #include <cstdint>
@@ -207,6 +208,11 @@ enum {
   /// - 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
@@ -265,12 +271,13 @@ public:
   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);
diff --git a/include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h b/include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h
index d4cb1326fb8..d5400177f82 100644
--- a/include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h
+++ b/include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h
@@ -273,12 +273,14 @@ bool InstructionSelector::executeMatchTable(
                    << "), 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 =
+          (ISel.*MatcherInfo.ComplexPredicates[ComplexPredicateID])(
+              State.MIs[InsnID]->getOperand(OpIdx));
+      if (Renderer.hasValue())
+        State.Renderers[RendererID] = Renderer.getValue();
+      else
         if (handleReject() == RejectAndGiveUp)
           return false;
-      }
       break;
     }
 
@@ -472,11 +474,23 @@ bool InstructionSelector::executeMatchTable(
       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++];
diff --git a/lib/CodeGen/GlobalISel/InstructionSelector.cpp b/lib/CodeGen/GlobalISel/InstructionSelector.cpp
index 46966ccd60c..e1cbb8dddfb 100644
--- a/lib/CodeGen/GlobalISel/InstructionSelector.cpp
+++ b/lib/CodeGen/GlobalISel/InstructionSelector.cpp
@@ -29,7 +29,7 @@
 using namespace llvm;
 
 InstructionSelector::MatcherState::MatcherState(unsigned MaxRenderers)
-    : Renderers(MaxRenderers, nullptr), MIs() {}
+    : Renderers(MaxRenderers, {}), MIs() {}
 
 InstructionSelector::InstructionSelector() = default;
 
diff --git a/lib/Target/AArch64/AArch64InstructionSelector.cpp b/lib/Target/AArch64/AArch64InstructionSelector.cpp
index 88259ffdf00..ca93d1feaa6 100644
--- a/lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ b/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -1367,13 +1367,13 @@ AArch64InstructionSelector::selectArithImmed(MachineOperand &Root) const {
   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;
 
@@ -1383,10 +1383,13 @@ AArch64InstructionSelector::selectArithImmed(MachineOperand &Root) const {
     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 {
diff --git a/test/TableGen/GlobalISelEmitter.td b/test/TableGen/GlobalISelEmitter.td
index f7ade225f2e..609d1c5ec51 100644
--- a/test/TableGen/GlobalISelEmitter.td
+++ b/test/TableGen/GlobalISelEmitter.td
@@ -31,6 +31,12 @@ def complex : Operand<i32>, ComplexPattern<i32, 2, "SelectComplexPattern", []> {
 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)>;
@@ -56,6 +62,7 @@ def HasC : Predicate<"Subtarget->hasC()"> { let RecomputePerFunction = 1; }
 // 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
 
@@ -107,6 +114,7 @@ def HasC : Predicate<"Subtarget->hasC()"> { let RecomputePerFunction = 1; }
 // CHECK-NEXT:  enum {
 // CHECK-NEXT:    GICP_Invalid,
 // CHECK-NEXT:    GICP_gi_complex,
+// CHECK-NEXT:    GICP_gi_complex_rr,
 // CHECK-NEXT:  };
 
 // CHECK-LABEL: // PatFrag predicates.
@@ -180,9 +188,13 @@ def HasC : Predicate<"Subtarget->hasC()"> { let RecomputePerFunction = 1; }
 // 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. --------------===//
 //
@@ -198,9 +210,9 @@ def : Pat<(select GPR32:$src1, complex:$src2, (select GPR32:$src3, complex:$src4
 // 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,
@@ -212,18 +224,20 @@ def : Pat<(select GPR32:$src1, complex:$src2, (select GPR32:$src3, complex:$src4
 // 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,
diff --git a/utils/TableGen/GlobalISelEmitter.cpp b/utils/TableGen/GlobalISelEmitter.cpp
index bbc396967c0..e19b4392689 100644
--- a/utils/TableGen/GlobalISelEmitter.cpp
+++ b/utils/TableGen/GlobalISelEmitter.cpp
@@ -203,7 +203,12 @@ std::string explainOperator(Record *Operator) {
   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.
@@ -514,10 +519,17 @@ class RuleMatcher {
 
   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;
 
@@ -547,6 +559,20 @@ public:
 
   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;
 
@@ -1540,6 +1566,9 @@ private:
   /// 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();
@@ -1547,19 +1576,26 @@ private:
 
 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;
   }
 };
 
@@ -2028,11 +2064,12 @@ private:
   Record *findNodeEquiv(Record *N) const;
 
   Error importRulePredicates(RuleMatcher &M, ArrayRef<Predicate> Predicates);
-  Expected<InstructionMatcher &>
-  createAndImportSelDAGMatcher(InstructionMatcher &InsnMatcher,
-                               const TreePatternNode *Src,
-                               unsigned &TempOpIdx) const;
-  Error importChildMatcher(InstructionMatcher &InsnMatcher,
+  Expected<InstructionMatcher &> createAndImportSelDAGMatcher(
+      RuleMatcher &Rule, InstructionMatcher &InsnMatcher,
+      const TreePatternNode *Src, unsigned &TempOpIdx) const;
+  Error importComplexPatternOperandMatcher(OperandMatcher &OM, Record *R,
+                                           unsigned &TempOpIdx) const;
+  Error importChildMatcher(RuleMatcher &Rule, InstructionMatcher &InsnMatcher,
                            const TreePatternNode *SrcChild, unsigned OpIdx,
                            unsigned &TempOpIdx) const;
   Expected<BuildMIAction &>
@@ -2096,10 +2133,9 @@ GlobalISelEmitter::importRulePredicates(RuleMatcher &M,
   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;
 
@@ -2196,8 +2232,8 @@ GlobalISelEmitter::createAndImportSelDAGMatcher(InstructionMatcher &InsnMatcher,
         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);
     }
   }
@@ -2205,7 +2241,20 @@ GlobalISelEmitter::createAndImportSelDAGMatcher(InstructionMatcher &InsnMatcher,
   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 {
@@ -2238,6 +2287,26 @@ Error GlobalISelEmitter::importChildMatcher(InstructionMatcher &InsnMatcher,
 
   // 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();
+    }
+
     auto MaybeInsnOperand = OM.addPredicate<InstructionOperandMatcher>(
         InsnMatcher.getRuleMatcher(), SrcChild->getName());
     if (!MaybeInsnOperand.hasValue()) {
@@ -2250,7 +2319,7 @@ Error GlobalISelEmitter::importChildMatcher(InstructionMatcher &InsnMatcher,
     // Map the node to a gMIR instruction.
     InstructionOperandMatcher &InsnOperand = **MaybeInsnOperand;
     auto InsnMatcherOrError = createAndImportSelDAGMatcher(
-        InsnOperand.getInsnMatcher(), SrcChild, TempOpIdx);
+        Rule, InsnOperand.getInsnMatcher(), SrcChild, TempOpIdx);
     if (auto Error = InsnMatcherOrError.takeError())
       return Error;
 
@@ -2283,17 +2352,8 @@ Error GlobalISelEmitter::importChildMatcher(InstructionMatcher &InsnMatcher,
     }
 
     // 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(
@@ -2315,6 +2375,14 @@ Error GlobalISelEmitter::importExplicitUseRenderer(
                         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.
@@ -2552,7 +2620,7 @@ Expected<RuleMatcher> GlobalISelEmitter::runOnPattern(const PatternToMatch &P) {
   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();