[GlobalISel][TableGen] Add support for SDNodeXForm

[volkan]

Summary

This patch adds CustomRenderer which renders the matched
operands to the specified instruction.

Targets can enable the matching of SDNodeXForm by adding
a definition that inherits from GICustomOperandRenderer and
GISDNodeXFormEquiv as follows.

def gi_imm8 : GICustomOperandRenderer<"renderImm8”>,

GISDNodeXFormEquiv<imm8_xform>;

Custom renderer functions should be of the form:
void render(MachineInstrBuilder &MIB, const MachineInstr &I);

[qcolombet]

lib/Target/AArch64/AArch64InstructionSelector.cpp

1531

Could you put the explicit type here?

In particular, this pattern looks strange:
auto CstVal
*CstVal;

At least, I would expect something along those lines:
auto *CstVal
*CstVal;

[volkan]

Replaced auto with the actual type to make the code easy to read.

[volkan]

lib/Target/AArch64/AArch64InstructionSelector.cpp

1531

It's because getConstantVRegVal returns Optional<int64_t>, I replaced auto with that. Also, I replaced *CstVal with CstVal.getValue().

[qcolombet]

Looks mostly good to me.

Two things:

• The test case doesn't seem to demonstrate what we are adding (see inline comment)
• We miss an entry in the GlobalISel doc to explain this new construction (to be fair we miss the whole TableGen support explanation) (could be a follow-up patch)

test/CodeGen/AArch64/GlobalISel/select-mul.mir

21

I'm confused, isn't the goal of the patch to be able to match the immediate variant here?

[volkan]

test/CodeGen/AArch64/GlobalISel/select-mul.mir

21

Yes, but the pattern it's trying to match is different.

def : Pat<(i64 (mul (sext GPR32:$Rn), (s64imm_32bit:$C))),
          (SMADDLrrr GPR32:$Rn, (MOVi32imm (trunc_imm imm:$C)), XZR)>;

Here, trunc_imm is an SDNodeXForm.

I'll add the pattern as a comment.

[volkan]

Added the pattern to the test file.

[dsanders]

LGTM with some nits fixed

include/llvm/Target/GlobalISel/Target.td

50–51

We should probably expand on this to say that it matches an MI and renders directly to the result instruction (without an intermediate node unlike SDNodeXForm)

58

This is a tiny nitpick, but MachineInstr variables are usually named MI

lib/Target/AArch64/AArch64InstrInfo.td

682

Indentation

lib/Target/AArch64/AArch64InstructionSelector.cpp

95

I -> MI

1528

I -> MI

utils/TableGen/GlobalISelEmitter.cpp

3707–3723

Given that these lambdas are the same, could we unify them in a 'orderByName' lambda or similar?

[volkan]

Updated based on Daniel's comments.

include/llvm/CodeGen/GlobalISel/InstructionSelector.h

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 operands to the specified instruction using a custom function
+  /// - InsnID - Instruction ID to modify
+  /// - OldInsnID - Instruction ID to get the matched operand from
+  /// - RendererFnID - Custom renderer function to call
+  GIR_CustomRenderer,
 
   /// 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.
struct MatcherState {
     std::vector<ComplexRendererFns::value_type> Renderers;
     RecordedMIVector MIs;
     DenseMap<unsigned, unsigned> TempRegisters;
 
     MatcherState(unsigned MaxRenderers);
   };
 
 public:
-  template <class PredicateBitset, class ComplexMatcherMemFn>
-  struct MatcherInfoTy {
+  template <class PredicateBitset, class ComplexMatcherMemFn,
+            class CustomRendererFn>
+  struct ISelInfoTy {
     const LLT *TypeObjects;
     const PredicateBitset *FeatureBitsets;
     const ComplexMatcherMemFn *ComplexPredicates;
+    const CustomRendererFn *CustomRenderers;
   };
 
 protected:
   InstructionSelector();
 
   /// Execute a given matcher table and return true if the match was successful
   /// and false otherwise.
   template <class TgtInstructionSelector, class PredicateBitset,
-            class ComplexMatcherMemFn>
+            class ComplexMatcherMemFn, class CustomRendererFn>
   bool executeMatchTable(
       TgtInstructionSelector &ISel, NewMIVector &OutMIs, MatcherState &State,
-      const MatcherInfoTy<PredicateBitset, ComplexMatcherMemFn> &MatcherInfo,
+      const ISelInfoTy<PredicateBitset, ComplexMatcherMemFn, CustomRendererFn>
+          &ISelInfo,
       const int64_t *MatchTable, const TargetInstrInfo &TII,
       MachineRegisterInfo &MRI, const TargetRegisterInfo &TRI,
       const RegisterBankInfo &RBI, const PredicateBitset &AvailableFeatures,
       CodeGenCoverage &CoverageInfo) const;
 
   virtual bool testImmPredicate_I64(unsigned, int64_t) const {
     llvm_unreachable("Subclasses must override this to use tablegen");
   }

include/llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h

 /// GlobalISel PatFrag Predicates
 enum {
   GIPFP_I64_Invalid = 0,
   GIPFP_APInt_Invalid = 0,
   GIPFP_APFloat_Invalid = 0,
 };
 
 template <class TgtInstructionSelector, class PredicateBitset,
-          class ComplexMatcherMemFn>
+          class ComplexMatcherMemFn, class CustomRendererFn>
 bool InstructionSelector::executeMatchTable(
     TgtInstructionSelector &ISel, NewMIVector &OutMIs, MatcherState &State,
-    const MatcherInfoTy<PredicateBitset, ComplexMatcherMemFn> &MatcherInfo,
+    const ISelInfoTy<PredicateBitset, ComplexMatcherMemFn, CustomRendererFn>
+        &ISelInfo,
     const int64_t *MatchTable, const TargetInstrInfo &TII,
     MachineRegisterInfo &MRI, const TargetRegisterInfo &TRI,
     const RegisterBankInfo &RBI, const PredicateBitset &AvailableFeatures,
     CodeGenCoverage &CoverageInfo) const {
   uint64_t CurrentIdx = 0;
   SmallVector<uint64_t, 8> OnFailResumeAt;
 
   enum RejectAction { RejectAndGiveUp, RejectAndResume };
while (true) {
     }
 
     case GIM_CheckFeatures: {
       int64_t ExpectedBitsetID = MatchTable[CurrentIdx++];
       DEBUG_WITH_TYPE(TgtInstructionSelector::getName(),
                       dbgs() << CurrentIdx
                              << ": GIM_CheckFeatures(ExpectedBitsetID="
                              << ExpectedBitsetID << ")\n");
-      if ((AvailableFeatures & MatcherInfo.FeatureBitsets[ExpectedBitsetID]) !=
-          MatcherInfo.FeatureBitsets[ExpectedBitsetID]) {
+      if ((AvailableFeatures & ISelInfo.FeatureBitsets[ExpectedBitsetID]) !=
+          ISelInfo.FeatureBitsets[ExpectedBitsetID]) {
         if (handleReject() == RejectAndGiveUp)
           return false;
       }
       break;
     }
 
     case GIM_CheckOpcode: {
       int64_t InsnID = MatchTable[CurrentIdx++];
case GIM_CheckType: {
       int64_t OpIdx = MatchTable[CurrentIdx++];
       int64_t TypeID = MatchTable[CurrentIdx++];
       DEBUG_WITH_TYPE(TgtInstructionSelector::getName(),
                       dbgs() << CurrentIdx << ": GIM_CheckType(MIs[" << InsnID
                              << "]->getOperand(" << OpIdx
                              << "), TypeID=" << TypeID << ")\n");
       assert(State.MIs[InsnID] != nullptr && "Used insn before defined");
       if (MRI.getType(State.MIs[InsnID]->getOperand(OpIdx).getReg()) !=
-          MatcherInfo.TypeObjects[TypeID]) {
+          ISelInfo.TypeObjects[TypeID]) {
         if (handleReject() == RejectAndGiveUp)
           return false;
       }
       break;
     }
     case GIM_CheckPointerToAny: {
       int64_t InsnID = MatchTable[CurrentIdx++];
       int64_t OpIdx = MatchTable[CurrentIdx++];
case GIM_CheckComplexPattern: {
                       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.
       ComplexRendererFns Renderer =
-          (ISel.*MatcherInfo.ComplexPredicates[ComplexPredicateID])(
+          (ISel.*ISelInfo.ComplexPredicates[ComplexPredicateID])(
               State.MIs[InsnID]->getOperand(OpIdx));
       if (Renderer.hasValue())
         State.Renderers[RendererID] = Renderer.getValue();
       else
         if (handleReject() == RejectAndGiveUp)
           return false;
       break;
     }
case GIR_CopyConstantAsSImm: {
       else
         llvm_unreachable("Expected Imm or CImm operand");
       DEBUG_WITH_TYPE(TgtInstructionSelector::getName(),
                       dbgs() << CurrentIdx << ": GIR_CopyConstantAsSImm(OutMIs["
                              << NewInsnID << "], MIs[" << OldInsnID << "])\n");
       break;
     }
 
+    case GIR_CustomRenderer: {
+      int64_t InsnID = MatchTable[CurrentIdx++];
+      int64_t OldInsnID = MatchTable[CurrentIdx++];
+      int64_t RendererFnID = MatchTable[CurrentIdx++];
+      assert(OutMIs[InsnID] && "Attempted to add to undefined instruction");
+      DEBUG_WITH_TYPE(TgtInstructionSelector::getName(),
+                      dbgs() << CurrentIdx << ": GIR_CustomRenderer(OutMIs["
+                             << InsnID << "], MIs[" << OldInsnID << "], "
+                             << RendererFnID << ")\n");
+      (ISel.*ISelInfo.CustomRenderers[RendererFnID])(OutMIs[InsnID],
+                                                     *State.MIs[OldInsnID]);
+      break;
+    }
     case GIR_ConstrainOperandRC: {
       int64_t InsnID = MatchTable[CurrentIdx++];
       int64_t OpIdx = MatchTable[CurrentIdx++];
       int64_t RCEnum = MatchTable[CurrentIdx++];
       assert(OutMIs[InsnID] && "Attempted to add to undefined instruction");
       constrainOperandRegToRegClass(*OutMIs[InsnID].getInstr(), OpIdx,
                                     *TRI.getRegClass(RCEnum), TII, TRI, RBI);
       DEBUG_WITH_TYPE(TgtInstructionSelector::getName(),
case GIR_EraseFromParent: {
       break;
     }
 
     case GIR_MakeTempReg: {
       int64_t TempRegID = MatchTable[CurrentIdx++];
       int64_t TypeID = MatchTable[CurrentIdx++];
 
       State.TempRegisters[TempRegID] =
-          MRI.createGenericVirtualRegister(MatcherInfo.TypeObjects[TypeID]);
+          MRI.createGenericVirtualRegister(ISelInfo.TypeObjects[TypeID]);
       DEBUG_WITH_TYPE(TgtInstructionSelector::getName(),
                       dbgs() << CurrentIdx << ": TempRegs[" << TempRegID
                              << "] = GIR_MakeTempReg(" << TypeID << ")\n");
       break;
     }
 
     case GIR_Coverage: {
       int64_t RuleID = MatchTable[CurrentIdx++];

include/llvm/Target/GlobalISel/SelectionDAGCompat.td

 def : GINodeEquiv<G_ATOMICRMW_UMIN, atomic_load_umin>;
 def : GINodeEquiv<G_ATOMICRMW_UMAX, atomic_load_umax>;
 
 // Specifies the GlobalISel equivalents for SelectionDAG's ComplexPattern.
 // Should be used on defs that subclass GIComplexOperandMatcher<>.
 class GIComplexPatternEquiv<ComplexPattern seldag> {
   ComplexPattern SelDAGEquivalent = seldag;
 }
+
+// Specifies the GlobalISel equivalents for SelectionDAG's SDNodeXForm.
+// Should be used on defs that subclass GICustomOperandRenderer<>.
+class GISDNodeXFormEquiv<SDNodeXForm seldag> {
+  SDNodeXForm SelDAGEquivalent = seldag;
+}

include/llvm/Target/GlobalISel/Target.td

class GIComplexOperandMatcher<LLT type, string matcherfn> {
   // the form:
   //   bool select(const MatchOperand &Root, MatchOperand &Result1)
   // and should have the same number of ResultX arguments as the number of
   // result operands. It must return true on successful match and false
   // otherwise. If it returns true, then all the ResultX arguments must be
   // overwritten.
   string MatcherFn = matcherfn;
 }
+
+// Defines a custom renderer. This is analogous to SDNodeXForm from
+// SelectionDAG.
+//
+// Definitions that inherit from this may also inherit from GISDNodeXFormEquiv
+// to enable the import of SelectionDAG patterns involving those SDNodeXForms.
+class GICustomOperandRenderer<string rendererfn> {
+  // The function renders the operand(s) of the matched instruction to
+  // the specified instruction. It should be of the form:
+  //   void render(MachineInstrBuilder &MIB, const MachineInstr &I)
+  string RendererFn = rendererfn;
+}

lib/Target/AArch64/AArch64InstrInfo.td

def s64imm_32bit : ImmLeaf<i64, [{
   return Imm64 >= std::numeric_limits<int32_t>::min() &&
          Imm64 <= std::numeric_limits<int32_t>::max();
 }]>;
 
 def trunc_imm : SDNodeXForm<imm, [{
   return CurDAG->getTargetConstant(N->getZExtValue(), SDLoc(N), MVT::i32);
 }]>;
 
+def gi_trunc_imm : GICustomOperandRenderer<"renderTruncImm">,
+                GISDNodeXFormEquiv<trunc_imm>;
+
 def : Pat<(i64 i64imm_32bit:$src),
           (SUBREG_TO_REG (i64 0), (MOVi32imm (trunc_imm imm:$src)), sub_32)>;
 
 // Materialize FP constants via MOVi32imm/MOVi64imm (MachO large code model).
 def bitcast_fpimm_to_i32 : SDNodeXForm<fpimm, [{
 return CurDAG->getTargetConstant(
   N->getValueAPF().bitcastToAPInt().getZExtValue(), SDLoc(N), MVT::i32);
 }]>;

lib/Target/AArch64/AArch64InstructionSelector.cpp

private:
 
   ComplexRendererFns selectAddrModeIndexed(MachineOperand &Root,
                                            unsigned Size) const;
   template <int Width>
   ComplexRendererFns selectAddrModeIndexed(MachineOperand &Root) const {
     return selectAddrModeIndexed(Root, Width / 8);
   }
 
+  void renderTruncImm(MachineInstrBuilder &MIB, const MachineInstr &I) const;
+
   const AArch64TargetMachine &TM;
   const AArch64Subtarget &STI;
   const AArch64InstrInfo &TII;
   const AArch64RegisterInfo &TRI;
   const AArch64RegisterBankInfo &RBI;
 
 #define GET_GLOBALISEL_PREDICATES_DECL
 #include "AArch64GenGlobalISel.inc"
if (selectAddrModeUnscaled(Root, Size).hasValue())
     return None;
 
   return {{
       [=](MachineInstrBuilder &MIB) { MIB.add(Root); },
       [=](MachineInstrBuilder &MIB) { MIB.addImm(0); },
   }};
 }
 
+void AArch64InstructionSelector::renderTruncImm(MachineInstrBuilder &MIB,
+                                                const MachineInstr &I) const {
+  const MachineRegisterInfo &MRI = I.getParent()->getParent()->getRegInfo();
+  assert(I.getOpcode() == TargetOpcode::G_CONSTANT && "Expected G_CONSTANT");
+  Optional<int64_t> CstVal = getConstantVRegVal(I.getOperand(0).getReg(), MRI);
+  assert(CstVal && "Expected constant value");
+  MIB.addImm(CstVal.getValue());
+}
+
 namespace llvm {
 InstructionSelector *
 createAArch64InstructionSelector(const AArch64TargetMachine &TM,
                                  AArch64Subtarget &Subtarget,
                                  AArch64RegisterBankInfo &RBI) {
   return new AArch64InstructionSelector(TM, Subtarget, RBI);
 }
 }

test/CodeGen/AArch64/GlobalISel/select-mul.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -O0 -mtriple=aarch64-- -run-pass=instruction-select -verify-machineinstrs -global-isel %s -o - | FileCheck %s
+---
+name:            mul_i64_sext_imm32
+legalized:       true
+regBankSelected: true
+
+registers:
+  - { id: 0, class: gpr }
+  - { id: 1, class: gpr }
+  - { id: 2, class: gpr }
+  - { id: 3, class: gpr }
+
+body:             |
+  bb.0:
+    liveins: %w0
+
+    ; CHECK-LABEL: name: mul_i64_sext_imm32
+    ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY %w0
+    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 3
+    ; CHECK: [[SMADDLrrr:%[0-9]+]]:gpr64 = SMADDLrrr [[COPY]], [[MOVi32imm]], %xzr
+    ; CHECK: %x0 = COPY [[SMADDLrrr]]
+    %0:gpr(s32) = COPY %w0
+    %1:gpr(s64) = G_SEXT %0(s32)
+    %2:gpr(s64) = G_CONSTANT i64 3
+    %3:gpr(s64) = G_MUL %1, %2
+    %x0 = COPY %3(s64)
+...
+
+

test/TableGen/GlobalISelEmitter.td

def gi_complex :
     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 cimm8_xform : SDNodeXForm<imm, [{
+    uint64_t Val = N->getZExtValue() << 1;
+    return CurDAG->getTargetConstant(Val, SDLoc(N), MVT::i64);
+  }]>;
+
+def cimm8 : Operand<i32>, ImmLeaf<i32, [{return isInt<8>(Imm);}], cimm8_xform>;
+
+def gi_cimm8 : GICustomOperandRenderer<"renderImm8">,
+                GISDNodeXFormEquiv<cimm8_xform>;
+
 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; }
 
 //===- Test the function boilerplate. -------------------------------------===//
 
 // CHECK: const unsigned MAX_SUBTARGET_PREDICATES = 3;
 // CHECK: using PredicateBitset = llvm::PredicateBitsetImpl<MAX_SUBTARGET_PREDICATES>;
 
 // CHECK-LABEL: #ifdef GET_GLOBALISEL_TEMPORARIES_DECL
 // CHECK-NEXT:    mutable MatcherState State;
 // CHECK-NEXT:    typedef ComplexRendererFns(MyTargetInstructionSelector::*ComplexMatcherMemFn)(MachineOperand &) const;
-// CHECK-NEXT:    const MatcherInfoTy<PredicateBitset, ComplexMatcherMemFn> MatcherInfo;
+// CHECK-NEXT:    typedef void(MyTargetInstructionSelector::*CustomRendererFn)(MachineInstrBuilder &, const MachineInstr&) const;
+// CHECK-NEXT:    const ISelInfoTy<PredicateBitset, ComplexMatcherMemFn, CustomRendererFn> ISelInfo;
 // CHECK-NEXT:    static MyTargetInstructionSelector::ComplexMatcherMemFn ComplexPredicateFns[];
+// CHECK-NEXT:    static MyTargetInstructionSelector::CustomRendererFn CustomRenderers[];
 // CHECK-NEXT:    bool testImmPredicate_I64(unsigned PredicateID, int64_t Imm) const override;
 // CHECK-NEXT:    bool testImmPredicate_APInt(unsigned PredicateID, const APInt &Imm) const override;
 // CHECK-NEXT:    bool testImmPredicate_APFloat(unsigned PredicateID, const APFloat &Imm) const override;
 // CHECK-NEXT:  #endif // ifdef GET_GLOBALISEL_TEMPORARIES_DECL
 
 // CHECK-LABEL: #ifdef GET_GLOBALISEL_TEMPORARIES_INIT
 // CHECK-NEXT:    , State(2),
-// CHECK-NEXT:    MatcherInfo({TypeObjects, FeatureBitsets, ComplexPredicateFns})
+// CHECK-NEXT:    ISelInfo({TypeObjects, FeatureBitsets, ComplexPredicateFns, CustomRenderers})
 // 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:  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:    GIPFP_I64_Predicate_cimm8 = GIPFP_I64_Invalid + 1,
+// CHECK-NEXT:    GIPFP_I64_Predicate_simm8,
 // CHECK-NEXT:  };
-// CHECK-NEXT:  bool MyTargetInstructionSelector::testImmPredicate_I64(unsigned PredicateID, int64_t Imm) const {
-// CHECK-NEXT:    switch (PredicateID) {
-// CHECK-NEXT:    case GIPFP_I64_Predicate_simm8: {
+
+
+// CHECK-NEXT: bool MyTargetInstructionSelector::testImmPredicate_I64(unsigned PredicateID, int64_t Imm) const {
+// CHECK-NEXT:   switch (PredicateID) {
+// CHECK-NEXT:   case GIPFP_I64_Predicate_cimm8: {
+// CHECK-NEXT:     return isInt<8>(Imm);
+// CHECK-NEXT:     llvm_unreachable("ImmediateCode should have returned");
+// CHECK-NEXT:     return false;
+// CHECK-NEXT:   }
+// CHECK-NEXT:   case GIPFP_I64_Predicate_simm8: {
 // CHECK-NEXT:      return isInt<8>(Imm);
-// CHECK-NEXT:      llvm_unreachable("ImmediateCode should have returned");
-// CHECK-NEXT:      return false;
-// CHECK-NEXT:    }
-// CHECK-NEXT:    }
-// CHECK-NEXT:    llvm_unreachable("Unknown predicate");
-// CHECK-NEXT:    return false;
-// CHECK-NEXT:  }
+// CHECK-NEXT:     llvm_unreachable("ImmediateCode should have returned");
+// CHECK-NEXT:     return false;
+// CHECK-NEXT:   }
+// CHECK-NEXT:   }
+// CHECK-NEXT:   llvm_unreachable("Unknown predicate");
+// CHECK-NEXT:   return false;
+// CHECK-NEXT: }
 
 // CHECK-LABEL: // PatFrag predicates.
 // CHECK-NEXT:  enum {
 // CHECK-NEXT:    GIPFP_APFloat_Predicate_fpimmz = GIPFP_APFloat_Invalid + 1,
 // CHECK-NEXT:  };
 // CHECK-NEXT:  bool MyTargetInstructionSelector::testImmPredicate_APFloat(unsigned PredicateID, const APFloat & Imm) const {
 // CHECK-NEXT:    switch (PredicateID) {
 // CHECK-NEXT:    case GIPFP_APFloat_Predicate_fpimmz: {

 
 // CHECK-LABEL: MyTargetInstructionSelector::ComplexMatcherMemFn
 // CHECK-NEXT:  MyTargetInstructionSelector::ComplexPredicateFns[] = {
 // CHECK-NEXT:    nullptr, // GICP_Invalid
 // CHECK-NEXT:    &MyTargetInstructionSelector::selectComplexPattern, // gi_complex
 // CHECK-NEXT:    &MyTargetInstructionSelector::selectComplexPatternRR, // gi_complex_rr
 // CHECK-NEXT:  }
 
+// CHECK-LABEL: // Custom renderers.
+// CHECK-NEXT: enum {
+// CHECK-NEXT:   GICR_Invalid,
+// CHECK-NEXT:   GICR_renderImm8,
+// CHECK-NEXT: };
+// CHECK-NEXT: MyTargetInstructionSelector::CustomRendererFn
+// CHECK-NEXT: MyTargetInstructionSelector::CustomRenderers[] = {
+// CHECK-NEXT:   nullptr, // GICP_Invalid
+// CHECK-NEXT:   &MyTargetInstructionSelector::renderImm8, // gi_cimm8
+// CHECK-NEXT: };
+
 // CHECK: bool MyTargetInstructionSelector::selectImpl(MachineInstr &I, CodeGenCoverage &CoverageInfo) const {
 // CHECK-NEXT: MachineFunction &MF = *I.getParent()->getParent();
 // CHECK-NEXT: MachineRegisterInfo &MRI = MF.getRegInfo();
 // CHECK:      AvailableFunctionFeatures = computeAvailableFunctionFeatures(&STI, &MF);
 // CHECK-NEXT: const PredicateBitset AvailableFeatures = getAvailableFeatures();
 // CHECK-NEXT: NewMIVector OutMIs;
 // CHECK-NEXT: State.MIs.clear();
 // CHECK-NEXT: State.MIs.push_back(&I);

 // CHECK-NEXT:    // (imm:{ *:[i32] }):$imm =>  (MOVimm:{ *:[i32] } (imm:{ *:[i32] }):$imm)
 // CHECK-NEXT:    GIR_BuildMI, /*InsnID*/0, /*Opcode*/MyTarget::MOVimm,
 // CHECK-NEXT:    GIR_Copy, /*NewInsnID*/0, /*OldInsnID*/0, /*OpIdx*/0, // dst
 // CHECK-NEXT:    GIR_CopyConstantAsSImm, /*NewInsnID*/0, /*OldInsnID*/0, // imm
 // CHECK-NEXT:    GIR_EraseFromParent, /*InsnID*/0,
 // CHECK-NEXT:    GIR_ConstrainSelectedInstOperands, /*InsnID*/0,
 // CHECK-NEXT:    GIR_Done,
 // CHECK-NEXT:  // Label [[LABEL_NUM]]: @[[LABEL]]
+
+def MOVimm : I<(outs GPR32:$dst), (ins i32imm:$imm), [(set GPR32:$dst, imm:$imm)]>;
+
+
+//===- Test a pattern with a custom renderer. -----------------------------===//
+// CHECK-NEXT:  GIM_Try, /*On fail goto*//*Label [[LABEL_NUM:[0-9]+]]*/ [[LABEL:[0-9]+]],
+// CHECK-NEXT:    GIM_CheckNumOperands, /*MI*/0, /*Expected*/2,
+// NOOPT-NEXT:    GIM_CheckOpcode, /*MI*/0, TargetOpcode::G_CONSTANT,
+// CHECK-NEXT:    GIM_CheckI64ImmPredicate, /*MI*/0, /*Predicate*/GIPFP_I64_Predicate_cimm8,
+// 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] Operand 1
+// CHECK-NEXT:    // No operand predicates
+// CHECK-NEXT:    // (imm:{ *:[i32] })<<P:Predicate_cimm8>><<X:cimm8_xform>>:$imm  =>  (MOVcimm8:{ *:[i32] } (cimm8_xform:{ *:[i32] } (imm:{ *:[i32] }):$imm))
+// CHECK-NEXT:    GIR_BuildMI, /*InsnID*/0, /*Opcode*/MyTarget::MOVcimm8,
+// CHECK-NEXT:    GIR_Copy, /*NewInsnID*/0, /*OldInsnID*/0, /*OpIdx*/0, // dst
+// CHECK-NEXT:    GIR_CustomRenderer, /*InsnID*/0, /*OldInsnID*/0, /*Renderer*/GICR_renderImm8, // imm
+// CHECK-NEXT:    GIR_EraseFromParent, /*InsnID*/0,
+// CHECK-NEXT:    GIR_ConstrainSelectedInstOperands, /*InsnID*/0,
+// CHECK-NEXT:    GIR_Done,
+// CHECK-NEXT:  // Label [[LABEL_NUM]]: @[[LABEL]]
 // Closing the G_CONSTANT group.
 // OPT-NEXT:      GIM_Reject,
 // OPT-NEXT:  GIR_Done,
 // OPT-NEXT:  // Label [[GRP_LABEL_NUM]]: @[[GRP_LABEL]]
-
-def MOVimm : I<(outs GPR32:$dst), (ins i32imm:$imm), [(set GPR32:$dst, imm:$imm)]>;
+def MOVcimm8 : I<(outs GPR32:$dst), (ins i32imm:$imm), [(set GPR32:$dst, cimm8:$imm)]>;
 
 //===- Test a simple pattern with a FP immediate and a predicate. ---------===//
 
 // OPT-NEXT:  GIM_Try, /*On fail goto*//*Label [[GRP_LABEL_NUM:[0-9]+]]*/ [[GRP_LABEL:[0-9]+]],
 // OPT-NEXT:    GIM_CheckOpcode, /*MI*/0, TargetOpcode::G_FCONSTANT,
 // CHECK-NEXT:  GIM_Try, /*On fail goto*//*Label [[LABEL_NUM:[0-9]+]]*/ [[LABEL:[0-9]+]],
 // CHECK-NEXT:    GIM_CheckNumOperands, /*MI*/0, /*Expected*/2,
 // NOOPT-NEXT:    GIM_CheckOpcode, /*MI*/0, TargetOpcode::G_FCONSTANT,

 // OPT-NEXT:  GIR_Done,
 // OPT-NEXT:  // Label [[GRP_LABEL_NUM]]: @[[GRP_LABEL]]
 
 def BR : I<(outs), (ins unknown:$target),
             [(br bb:$target)]>;
 
 // CHECK-NEXT:    GIM_Reject,
 // CHECK-NEXT:  };
-// CHECK-NEXT:  if (executeMatchTable(*this, OutMIs, State, MatcherInfo, MatchTable0, TII, MRI, TRI, RBI, AvailableFeatures, CoverageInfo)) {
+// CHECK-NEXT:  if (executeMatchTable(*this, OutMIs, State, ISelInfo, MatchTable0, TII, MRI, TRI, RBI, AvailableFeatures, CoverageInfo)) {
 // CHECK-NEXT:    return true;
 // CHECK-NEXT:  }

utils/TableGen/GlobalISelEmitter.cpp

std::string explainOperator(Record *Operator) {
   if (Operator->isSubClassOf("Intrinsic"))
     return (" (Operator is an Intrinsic, " + Operator->getName() + ")").str();
 
   if (Operator->isSubClassOf("ComplexPattern"))
     return (" (Operator is an unmapped ComplexPattern, " + Operator->getName() +
             ")")
         .str();
 
+  if (Operator->isSubClassOf("SDNodeXForm"))
+    return (" (Operator is an unmapped SDNodeXForm, " + 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());
 }
 
for (const auto &Predicate : N->getPredicateFns()) {
     Explanation = Separator + "Has a predicate (" + explainPredicates(N) + ")";
     Separator = ", ";
     Explanation += (Separator + "first-failing:" +
                     Predicate.getOrigPatFragRecord()->getRecord()->getName())
                        .str();
     break;
   }
 
-  if (N->getTransformFn()) {
-    Explanation += Separator + "Has a transform function";
-    Separator = ", ";
-  }
-
-  if (!HasUnsupportedPredicate && !N->getTransformFn())
+  if (!HasUnsupportedPredicate)
     return Error::success();
 
   return failedImport(Explanation);
 }
 
 static Record *getInitValueAsRegClass(Init *V) {
   if (DefInit *VDefInit = dyn_cast<DefInit>(V)) {
     if (VDefInit->getDef()->isSubClassOf("RegisterOperand"))
enum RendererKind {
     OR_Copy,
     OR_CopyOrAddZeroReg,
     OR_CopySubReg,
     OR_CopyConstantAsImm,
     OR_CopyFConstantAsFPImm,
     OR_Imm,
     OR_Register,
     OR_TempRegister,
-    OR_ComplexPattern
+    OR_ComplexPattern,
+    OR_Custom
   };
 
 protected:
   RendererKind Kind;
 
 public:
   OperandRenderer(RendererKind Kind) : Kind(Kind) {}
   virtual ~OperandRenderer() {}
Table << MatchTable::Opcode(SubOperand.hasValue() ? "GIR_ComplexSubOperandRenderer"
           << MatchTable::IntValue(RendererID);
     if (SubOperand.hasValue())
       Table << MatchTable::Comment("SubOperand")
             << MatchTable::IntValue(SubOperand.getValue());
     Table << MatchTable::Comment(SymbolicName) << MatchTable::LineBreak;
   }
 };
 
+class CustomRenderer : public OperandRenderer {
+protected:
+  unsigned InsnID;
+  const Record &Renderer;
+  /// The name of the operand.
+  const std::string SymbolicName;
+
+public:
+  CustomRenderer(unsigned InsnID, const Record &Renderer,
+                 StringRef SymbolicName)
+      : OperandRenderer(OR_Custom), InsnID(InsnID), Renderer(Renderer),
+        SymbolicName(SymbolicName) {}
+
+  static bool classof(const OperandRenderer *R) {
+    return R->getKind() == OR_Custom;
+  }
+
+  void emitRenderOpcodes(MatchTable &Table, RuleMatcher &Rule) const override {
+    const InstructionMatcher &InsnMatcher =
+        Rule.getInstructionMatcher(SymbolicName);
+    unsigned OldInsnVarID = Rule.getInsnVarID(InsnMatcher);
+    Table << MatchTable::Opcode("GIR_CustomRenderer")
+          << MatchTable::Comment("InsnID") << MatchTable::IntValue(InsnID)
+          << MatchTable::Comment("OldInsnID")
+          << MatchTable::IntValue(OldInsnVarID)
+          << MatchTable::Comment("Renderer")
+          << MatchTable::NamedValue(
+                 "GICR_" + Renderer.getValueAsString("RendererFn").str())
+          << 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.
 class MatchAction {
 public:
   virtual ~MatchAction() {}
private:
   /// This is defined using 'GINodeEquiv' in the target description.
   DenseMap<Record *, Record *> NodeEquivs;
 
   /// Keep track of the equivalence between ComplexPattern's and
   /// GIComplexOperandMatcher. Map entries are specified by subclassing
   /// GIComplexPatternEquiv.
   DenseMap<const Record *, const Record *> ComplexPatternEquivs;
 
+  /// Keep track of the equivalence between SDNodeXForm's and
+  /// GICustomOperandRenderer. Map entries are specified by subclassing
+  /// GISDNodeXFormEquiv.
+  DenseMap<const Record *, const Record *> SDNodeXFormEquivs;
+
   // Map of predicates to their subtarget features.
   SubtargetFeatureInfoMap SubtargetFeatures;
 
   // Rule coverage information.
   Optional<CodeGenCoverage> RuleCoverage;
 
   void gatherNodeEquivs();
   Record *findNodeEquiv(Record *N) const;
void GlobalISelEmitter::gatherNodeEquivs() {
 
   assert(ComplexPatternEquivs.empty());
   for (Record *Equiv : RK.getAllDerivedDefinitions("GIComplexPatternEquiv")) {
     Record *SelDAGEquiv = Equiv->getValueAsDef("SelDAGEquivalent");
     if (!SelDAGEquiv)
       continue;
     ComplexPatternEquivs[SelDAGEquiv] = Equiv;
  }
+
+ assert(SDNodeXFormEquivs.empty());
+ for (Record *Equiv : RK.getAllDerivedDefinitions("GISDNodeXFormEquiv")) {
+   Record *SelDAGEquiv = Equiv->getValueAsDef("SelDAGEquivalent");
+   if (!SelDAGEquiv)
+     continue;
+   SDNodeXFormEquivs[SelDAGEquiv] = Equiv;
+ }
 }
 
 Record *GlobalISelEmitter::findNodeEquiv(Record *N) const {
   return NodeEquivs.lookup(N);
 }
 
 GlobalISelEmitter::GlobalISelEmitter(RecordKeeper &RK)
     : RK(RK), CGP(RK, [&](TreePattern *P) { fixupPatternTrees(P); }),
Error GlobalISelEmitter::importChildMatcher(RuleMatcher &Rule,
   }
 
   return failedImport("Src pattern child is an unsupported kind");
 }
 
 Expected<action_iterator> GlobalISelEmitter::importExplicitUseRenderer(
     action_iterator InsertPt, RuleMatcher &Rule, BuildMIAction &DstMIBuilder,
     TreePatternNode *DstChild) {
-  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>(
         *std::get<0>(*SubOperand), DstChild->getName(),
         std::get<1>(*SubOperand), std::get<2>(*SubOperand));
     return InsertPt;
   }
 
   if (!DstChild->isLeaf()) {
+
+    if (DstChild->getOperator()->isSubClassOf("SDNodeXForm")) {
+      auto Child = DstChild->getChild(0);
+      auto I = SDNodeXFormEquivs.find(DstChild->getOperator());
+      if (I != SDNodeXFormEquivs.end()) {
+        DstMIBuilder.addRenderer<CustomRenderer>(*I->second, Child->getName());
+        return InsertPt;
+      }
+      return failedImport("SDNodeXForm " + Child->getName() +
+                          " has no custom renderer");
+    }
+
     // 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>(DstChild->getName());
         return InsertPt;
       }
if (ChildRec->isSubClassOf("ComplexPattern")) {
 
       const OperandMatcher &OM = Rule.getOperandMatcher(DstChild->getName());
       DstMIBuilder.addRenderer<RenderComplexPatternOperand>(
           *ComplexPattern->second, DstChild->getName(),
           OM.getAllocatedTemporariesBaseID());
       return InsertPt;
     }
 
-    if (ChildRec->isSubClassOf("SDNodeXForm"))
-      return failedImport("Dst pattern child def is an unsupported tablegen "
-                          "class (SDNodeXForm)");
-
     return failedImport(
         "Dst pattern child def is an unsupported tablegen class");
   }
 
   return failedImport("Dst pattern child is an unsupported kind");
 }
 
 Expected<BuildMIAction &> GlobalISelEmitter::createAndImportInstructionRenderer(
if (RuleCoverage) {
         PrintWarning(Pat.getSrcRecord()->getLoc(),
                      "Pattern is not covered by a test");
     }
     Rules.push_back(std::move(MatcherOrErr.get()));
   }
 
   std::vector<Record *> ComplexPredicates =
       RK.getAllDerivedDefinitions("GIComplexOperandMatcher");
   std::sort(ComplexPredicates.begin(), ComplexPredicates.end(),
             [](const Record *A, const Record *B) {
               if (A->getName() < B->getName())
                 return true;
               return false;
             });
+
+  std::vector<Record *> CustomRendererFns =
+      RK.getAllDerivedDefinitions("GICustomOperandRenderer");
+  std::sort(CustomRendererFns.begin(), CustomRendererFns.end(),
+            [](const Record *A, const Record *B) {
+              if (A->getName() < B->getName())
+                return true;
+              return false;
+            });
+
   unsigned MaxTemporaries = 0;
   for (const auto &Rule : Rules)
     MaxTemporaries = std::max(MaxTemporaries, Rule.countRendererFns());
 
   OS << "#ifdef GET_GLOBALISEL_PREDICATE_BITSET\n"
      << "const unsigned MAX_SUBTARGET_PREDICATES = " << SubtargetFeatures.size()
      << ";\n"
      << "using PredicateBitset = "
         "llvm::PredicateBitsetImpl<MAX_SUBTARGET_PREDICATES>;\n"
      << "#endif // ifdef GET_GLOBALISEL_PREDICATE_BITSET\n\n";
 
   OS << "#ifdef GET_GLOBALISEL_TEMPORARIES_DECL\n"
      << "  mutable MatcherState State;\n"
      << "  typedef "
         "ComplexRendererFns("
      << Target.getName()
      << "InstructionSelector::*ComplexMatcherMemFn)(MachineOperand &) const;\n"
-     << "  const MatcherInfoTy<PredicateBitset, ComplexMatcherMemFn> "
-        "MatcherInfo;\n"
-     << "  static " << Target.getName()
+
+     << "  typedef void(" << Target.getName()
+     << "InstructionSelector::*CustomRendererFn)(MachineInstrBuilder &, const "
+        "MachineInstr&) "
+        "const;\n"
+     << "  const ISelInfoTy<PredicateBitset, ComplexMatcherMemFn, "
+        "CustomRendererFn> "
+        "ISelInfo;\n";
+  OS << "  static " << Target.getName()
      << "InstructionSelector::ComplexMatcherMemFn ComplexPredicateFns[];\n"
+     << "  static " << Target.getName()
+     << "InstructionSelector::CustomRendererFn CustomRenderers[];\n"
      << "bool testImmPredicate_I64(unsigned PredicateID, int64_t Imm) const "
         "override;\n"
      << "bool testImmPredicate_APInt(unsigned PredicateID, const APInt &Imm) "
         "const override;\n"
      << "bool testImmPredicate_APFloat(unsigned PredicateID, const APFloat "
         "&Imm) const override;\n"
      << "#endif // ifdef GET_GLOBALISEL_TEMPORARIES_DECL\n\n";
 
   OS << "#ifdef GET_GLOBALISEL_TEMPORARIES_INIT\n"
      << ", State(" << MaxTemporaries << "),\n"
-     << "MatcherInfo({TypeObjects, FeatureBitsets, ComplexPredicateFns})\n"
+     << "ISelInfo({TypeObjects, FeatureBitsets, ComplexPredicateFns, "
+        "CustomRenderers})\n"
      << "#endif // ifdef GET_GLOBALISEL_TEMPORARIES_INIT\n\n";
 
   OS << "#ifdef GET_GLOBALISEL_IMPL\n";
   SubtargetFeatureInfo::emitSubtargetFeatureBitEnumeration(SubtargetFeatures,
                                                            OS);
 
   // Separate subtarget features by how often they must be recomputed.
   SubtargetFeatureInfoMap ModuleFeatures;
OS << Target.getName() << "InstructionSelector::ComplexMatcherMemFn\n"
      << Target.getName() << "InstructionSelector::ComplexPredicateFns[] = {\n"
      << "  nullptr, // GICP_Invalid\n";
   for (const auto &Record : ComplexPredicates)
     OS << "  &" << Target.getName()
        << "InstructionSelector::" << Record->getValueAsString("MatcherFn")
        << ", // " << Record->getName() << "\n";
   OS << "};\n\n";
 
+  OS << "// Custom renderers.\n"
+     << "enum {\n"
+     << "  GICR_Invalid,\n";
+  for (const auto &Record : CustomRendererFns)
+    OS << "  GICR_" << Record->getValueAsString("RendererFn") << ", \n";
+  OS << "};\n";
+
+  OS << Target.getName() << "InstructionSelector::CustomRendererFn\n"
+     << Target.getName() << "InstructionSelector::CustomRenderers[] = {\n"
+     << "  nullptr, // GICP_Invalid\n";
+  for (const auto &Record : CustomRendererFns)
+    OS << "  &" << Target.getName()
+       << "InstructionSelector::" << Record->getValueAsString("RendererFn")
+       << ", // " << Record->getName() << "\n";
+  OS << "};\n\n";
+
   OS << "bool " << Target.getName()
      << "InstructionSelector::selectImpl(MachineInstr &I, CodeGenCoverage "
         "&CoverageInfo) const {\n"
      << "  MachineFunction &MF = *I.getParent()->getParent();\n"
      << "  MachineRegisterInfo &MRI = MF.getRegInfo();\n"
      << "  // FIXME: This should be computed on a per-function basis rather "
         "than per-insn.\n"
      << "  AvailableFunctionFeatures = computeAvailableFunctionFeatures(&STI, "
void GlobalISelEmitter::run(raw_ostream &OS) {
 
   MatchTable Table(0);
   for (Matcher *Rule : OptRules) {
     Rule->emit(Table);
     ++NumPatternEmitted;
   }
   Table << MatchTable::Opcode("GIM_Reject") << MatchTable::LineBreak;
   Table.emitDeclaration(OS);
-  OS << "  if (executeMatchTable(*this, OutMIs, State, MatcherInfo, ";
+  OS << "  if (executeMatchTable(*this, OutMIs, State, ISelInfo, ";
   Table.emitUse(OS);
   OS << ", TII, MRI, TRI, RBI, AvailableFeatures, CoverageInfo)) {\n"
      << "    return true;\n"
      << "  }\n\n";
 
   OS << "  return false;\n"
      << "}\n"
      << "#endif // ifdef GET_GLOBALISEL_IMPL\n";