[GlobalISel] Base implementation for sret demotion.

[cdevadas]

Summary

If the return values can't be lowered to registers
SelectionDAG perform the sret demotion. This patch
contains the basic implementation for the same in
the GlobalISel pipeline.

Furthermore, targets should bring relevant changes
during lowerFormalArguments, lowerReturn and
lowerCall to make use of this feature.

[paquette]

Thanks for working on this!

Can you include a testcase for this?

[cdevadas]

Not sure I can have one at this point.
There is a follow-up patch I am making to enable it for AMDGPU. I will have some tests along with that.

[arsenm]

llvm/lib/CodeGen/GlobalISel/CallLowering.cpp

578–587

I think something is off here because this shouldn't depend on the NumRegistersForCallingConv code

llvm/tools/llvm-exegesis/lib/Assembler.cpp

124–138

I'm surprised this is here

[cdevadas]

llvm/lib/CodeGen/GlobalISel/CallLowering.cpp

578–587

Why do you think so?
getNumRegistersForCallingConv helps here to get the actual number of target registers required for the return type.

[arsenm]

llvm/lib/CodeGen/GlobalISel/CallLowering.cpp

578–587

Nevermind, I have this backwards

[cdevadas]

Ping

[cdevadas]

Ping

[arsenm]

llvm/include/llvm/CodeGen/GlobalISel/CallLowering.h

318–320

s/handle/insert/?

Should this return DemoteReg rather than accept it as an argument?

llvm/include/llvm/CodeGen/GlobalISel/CallLowering.h

 #ifndef LLVM_CODEGEN_GLOBALISEL_CALLLOWERING_H
 #define LLVM_CODEGEN_GLOBALISEL_CALLLOWERING_H
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/CodeGen/CallingConvLower.h"
 #include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/CodeGen/TargetCallingConv.h"
+#include "llvm/IR/Attributes.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/Type.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MachineValueType.h"
 #include <cstdint>
 #include <functional>
 
 namespace llvm {
 
 class CallBase;
 class DataLayout;
 class Function;
+class FunctionLoweringInfo;
 class MachineIRBuilder;
 struct MachinePointerInfo;
 class MachineRegisterInfo;
 class TargetLowering;
 class Value;
 
 class CallLowering {
   const TargetLowering *TLI;
 
   virtual void anchor();
 public:
-  struct ArgInfo {
+  struct BaseArgInfo {
+    Type *Ty;
+    SmallVector<ISD::ArgFlagsTy, 4> Flags;
+    bool IsFixed;
+
+    BaseArgInfo(Type *Ty,
+                ArrayRef<ISD::ArgFlagsTy> Flags = ArrayRef<ISD::ArgFlagsTy>(),
+                bool IsFixed = true)
+        : Ty(Ty), Flags(Flags.begin(), Flags.end()), IsFixed(IsFixed) {}
+
+    BaseArgInfo() : Ty(nullptr), IsFixed(false) {}
+  };
+
+  struct ArgInfo : public BaseArgInfo {
     SmallVector<Register, 4> Regs;
     // If the argument had to be split into multiple parts according to the
     // target calling convention, then this contains the original vregs
     // if the argument was an incoming arg.
     SmallVector<Register, 2> OrigRegs;
-    Type *Ty;
-    SmallVector<ISD::ArgFlagsTy, 4> Flags;
-    bool IsFixed;
 
     ArgInfo(ArrayRef<Register> Regs, Type *Ty,
             ArrayRef<ISD::ArgFlagsTy> Flags = ArrayRef<ISD::ArgFlagsTy>(),
             bool IsFixed = true)
-        : Regs(Regs.begin(), Regs.end()), Ty(Ty),
-          Flags(Flags.begin(), Flags.end()), IsFixed(IsFixed) {
+        : BaseArgInfo(Ty, Flags, IsFixed), Regs(Regs.begin(), Regs.end()) {
       if (!Regs.empty() && Flags.empty())
         this->Flags.push_back(ISD::ArgFlagsTy());
       // FIXME: We should have just one way of saying "no register".
       assert(((Ty->isVoidTy() || Ty->isEmptyTy()) ==
               (Regs.empty() || Regs[0] == 0)) &&
              "only void types should have no register");
     }
 
-    ArgInfo() : Ty(nullptr), IsFixed(false) {}
+    ArgInfo() : BaseArgInfo() {}
   };
 
   struct CallLoweringInfo {
     /// Calling convention to be used for the call.
     CallingConv::ID CallConv = CallingConv::C;
 
     /// Destination of the call. It should be either a register, globaladdress,
     /// or externalsymbol.
struct CallLoweringInfo {
     bool IsTailCall = false;
 
     /// True if the call was lowered as a tail call. This is consumed by the
     /// legalizer. This allows the legalizer to lower libcalls as tail calls.
     bool LoweredTailCall = false;
 
     /// True if the call is to a vararg function.
     bool IsVarArg = false;
+
+    /// True if the function's return value can be lowered to registers.
+    bool CanLowerReturn = true;
+
+    /// VReg to hold the hidden sret parameter.
+    Register DemoteRegister;
+
+    /// The stack index for sret demotion.
+    int DemoteStackIndex;
   };
 
   /// Argument handling is mostly uniform between the four places that
   /// make these decisions: function formal arguments, call
   /// instruction args, call instruction returns and function
   /// returns. However, once a decision has been made on where an
   /// argument should go, exactly what happens can vary slightly. This
   /// class abstracts the differences.
public:
 
   /// \return true if the target is capable of handling swifterror values that
   /// have been promoted to a specified register. The extended versions of
   /// lowerReturn and lowerCall should be implemented.
   virtual bool supportSwiftError() const {
     return false;
   }
 
+  /// Load the returned value from the stack into virtual registers in \p VRegs.
+  /// It uses the frame index \p FI and the start offset from \p DemoteReg.
+  /// The loaded data size will be determined from \p RetTy.
+  void handleSRetLoads(MachineIRBuilder &MIRBuilder, Type *RetTy,
+                       ArrayRef<Register> VRegs, Register DemoteReg,
+                       int FI) const;
+
+  /// Store the return value given by \p VRegs into stack starting at the offset
+  /// specified in \p DemoteReg.
+  void handleSRetStores(MachineIRBuilder &MIRBuilder, Type *RetTy,
+                        ArrayRef<Register> VRegs, Register DemoteReg) const;
+
+  /// Insert the hidden sret ArgInfo to the beginning of \p SplitArgs.
+  /// This function should be called from the target specific
+  /// lowerFormalArguments when \p F requires the sret demotion.
+  void insertSRetIncomingArgument(const Function &F,
+                                  SmallVectorImpl<ArgInfo> &SplitArgs,
+                                  Register &DemoteReg, MachineRegisterInfo &MRI,
+                                  const DataLayout &DL) const;
+
+  /// For the call-base described by \p CB, insert the hidden sret ArgInfo to
+  /// the OrigArgs field of \p Info.
+  void insertSRetOutgoingArgument(MachineIRBuilder &MIRBuilder,
+                                  const CallBase &CB,
+                                  CallLoweringInfo &Info) const;
+
+  /// \return True if the return type described by \p Outs can be returned
+  /// without performing sret demotion.
+  bool checkReturn(CCState &CCInfo, SmallVectorImpl<BaseArgInfo> &Outs,
+                   CCAssignFn *Fn) const;
+
+  /// Get the type and the ArgFlags for the split components of \p RetTy as
+  /// returned by \c ComputeValueVTs.
+  void getReturnInfo(CallingConv::ID CallConv, Type *RetTy, AttributeList Attrs,
+                     SmallVectorImpl<BaseArgInfo> &Outs,
+                     const DataLayout &DL) const;
+
+  /// Toplevel function to check the return type based on the target calling
+  /// convention. \return True if the return value of \p MF can be returned
+  /// without performing sret demotion.
+  bool checkReturnTypeForCallConv(MachineFunction &MF) const;
+
+  /// This hook must be implemented to check whether the return values
+  /// described by \p Outs can fit into the return registers. If false
+  /// is returned, an sret-demotion is performed.
+  virtual bool canLowerReturn(MachineFunction &MF, CallingConv::ID CallConv,
+                              SmallVectorImpl<BaseArgInfo> &Outs, bool IsVarArg,
+                              LLVMContext &Context) const {
+    return true;
+  }
+
   /// This hook must be implemented to lower outgoing return values, described
   /// by \p Val, into the specified virtual registers \p VRegs.
   /// This hook is used by GlobalISel.
   ///
+  /// \p FLI is required for sret demotion.
+  ///
   /// \p SwiftErrorVReg is non-zero if the function has a swifterror parameter
   /// that needs to be implicitly returned.
   ///
   /// \return True if the lowering succeeds, false otherwise.
   virtual bool lowerReturn(MachineIRBuilder &MIRBuilder, const Value *Val,
-                           ArrayRef<Register> VRegs,
+                           ArrayRef<Register> VRegs, FunctionLoweringInfo &FLI,
                            Register SwiftErrorVReg) const {
     if (!supportSwiftError()) {
       assert(SwiftErrorVReg == 0 && "attempt to use unsupported swifterror");
-      return lowerReturn(MIRBuilder, Val, VRegs);
+      return lowerReturn(MIRBuilder, Val, VRegs, FLI);
     }
     return false;
   }
 
   /// This hook behaves as the extended lowerReturn function, but for targets
   /// that do not support swifterror value promotion.
   virtual bool lowerReturn(MachineIRBuilder &MIRBuilder, const Value *Val,
-                           ArrayRef<Register> VRegs) const {
+                           ArrayRef<Register> VRegs,
+                           FunctionLoweringInfo &FLI) const {
     return false;
   }
 
   virtual bool fallBackToDAGISel(const Function &F) const { return false; }
 
   /// This hook must be implemented to lower the incoming (formal)
   /// arguments, described by \p VRegs, for GlobalISel. Each argument
   /// must end up in the related virtual registers described by \p VRegs.
   /// In other words, the first argument should end up in \c VRegs[0],
   /// the second in \c VRegs[1], and so on. For each argument, there will be one
   /// register for each non-aggregate type, as returned by \c computeValueLLTs.
   /// \p MIRBuilder is set to the proper insertion for the argument
-  /// lowering.
+  /// lowering. \p FLI is required for sret demotion.
   ///
   /// \return True if the lowering succeeded, false otherwise.
   virtual bool lowerFormalArguments(MachineIRBuilder &MIRBuilder,
                                     const Function &F,
-                                    ArrayRef<ArrayRef<Register>> VRegs) const {
+                                    ArrayRef<ArrayRef<Register>> VRegs,
+                                    FunctionLoweringInfo &FLI) const {
     return false;
   }
 
   /// This hook must be implemented to lower the given call instruction,
   /// including argument and return value marshalling.
   ///
   ///
   /// \return true if the lowering succeeded, false otherwise.

llvm/lib/CodeGen/GlobalISel/CallLowering.cpp

bool CallLowering::lowerCall(MachineIRBuilder &MIRBuilder, const CallBase &CB,
   const DataLayout &DL = MIRBuilder.getDataLayout();
   MachineFunction &MF = MIRBuilder.getMF();
   bool CanBeTailCalled = CB.isTailCall() &&
                          isInTailCallPosition(CB, MF.getTarget()) &&
                          (MF.getFunction()
                               .getFnAttribute("disable-tail-calls")
                               .getValueAsString() != "true");
 
+  CallingConv::ID CallConv = CB.getCallingConv();
+  Type *RetTy = CB.getType();
+  bool IsVarArg = CB.getFunctionType()->isVarArg();
+
+  SmallVector<BaseArgInfo, 4> SplitArgs;
+  getReturnInfo(CallConv, RetTy, CB.getAttributes(), SplitArgs, DL);
+  Info.CanLowerReturn =
+      canLowerReturn(MF, CallConv, SplitArgs, IsVarArg, RetTy->getContext());
+
+  if (!Info.CanLowerReturn) {
+    // Callee requires sret demotion.
+    insertSRetOutgoingArgument(MIRBuilder, CB, Info);
+
+    // The sret demotion isn't compatible with tail-calls, since the sret
+    // argument points into the caller's stack frame.
+    CanBeTailCalled = false;
+  }
+
   // First step is to marshall all the function's parameters into the correct
   // physregs and memory locations. Gather the sequence of argument types that
   // we'll pass to the assigner function.
   unsigned i = 0;
   unsigned NumFixedArgs = CB.getFunctionType()->getNumParams();
   for (auto &Arg : CB.args()) {
     ArgInfo OrigArg{ArgRegs[i], Arg->getType(), getAttributesForArgIdx(CB, i),
                     i < NumFixedArgs};
bool CallLowering::lowerCall(MachineIRBuilder &MIRBuilder, const CallBase &CB,
   // Try looking through a bitcast from one function type to another.
   // Commonly happens with calls to objc_msgSend().
   const Value *CalleeV = CB.getCalledOperand()->stripPointerCasts();
   if (const Function *F = dyn_cast<Function>(CalleeV))
     Info.Callee = MachineOperand::CreateGA(F, 0);
   else
     Info.Callee = MachineOperand::CreateReg(GetCalleeReg(), false);
 
-  Info.OrigRet = ArgInfo{ResRegs, CB.getType(), ISD::ArgFlagsTy{}};
+  Info.OrigRet = ArgInfo{ResRegs, RetTy, ISD::ArgFlagsTy{}};
   if (!Info.OrigRet.Ty->isVoidTy())
     setArgFlags(Info.OrigRet, AttributeList::ReturnIndex, DL, CB);
 
   Info.KnownCallees = CB.getMetadata(LLVMContext::MD_callees);
-  Info.CallConv = CB.getCallingConv();
+  Info.CallConv = CallConv;
   Info.SwiftErrorVReg = SwiftErrorVReg;
   Info.IsMustTailCall = CB.isMustTailCall();
   Info.IsTailCall = CanBeTailCalled;
-  Info.IsVarArg = CB.getFunctionType()->isVarArg();
+  Info.IsVarArg = IsVarArg;
   return lowerCall(MIRBuilder, Info);
 }
 
 template <typename FuncInfoTy>
 void CallLowering::setArgFlags(CallLowering::ArgInfo &Arg, unsigned OpIdx,
                                const DataLayout &DL,
                                const FuncInfoTy &FuncInfo) const {
   auto &Flags = Arg.Flags[0];
for (unsigned i = 0, e = Args.size(), j = 0; i != e; ++i, ++j) {
     }
 
     j += NumArgRegs - 1;
   }
 
   return true;
 }
 
+void CallLowering::handleSRetLoads(MachineIRBuilder &MIRBuilder, Type *RetTy,
+                                   ArrayRef<Register> VRegs, Register DemoteReg,
+                                   int FI) const {
+  MachineFunction &MF = MIRBuilder.getMF();
+  MachineRegisterInfo &MRI = MF.getRegInfo();
+  const DataLayout &DL = MF.getDataLayout();
+
+  SmallVector<EVT, 4> SplitVTs;
+  SmallVector<uint64_t, 4> Offsets;
+  ComputeValueVTs(*TLI, DL, RetTy, SplitVTs, &Offsets, 0);
+
+  assert(VRegs.size() == SplitVTs.size());
+
+  unsigned NumValues = SplitVTs.size();
+  Align BaseAlign = DL.getPrefTypeAlign(RetTy);
+  Type *RetPtrTy = RetTy->getPointerTo(DL.getAllocaAddrSpace());
+  LLT OffsetLLTy = getLLTForType(*DL.getIntPtrType(RetPtrTy), DL);
+
+  MachinePointerInfo PtrInfo = MachinePointerInfo::getFixedStack(MF, FI);
+
+  for (unsigned I = 0; I < NumValues; ++I) {
+    Register Addr;
+    MIRBuilder.materializePtrAdd(Addr, DemoteReg, OffsetLLTy, Offsets[I]);
+    auto MMO = MF.getMachineMemOperand(PtrInfo, MachineMemOperand::MOLoad,
+                                       MRI.getType(VRegs[I]).getSizeInBytes(),
+                                       commonAlignment(BaseAlign, Offsets[I]));
+    MIRBuilder.buildLoad(VRegs[I], Addr, *MMO);
+  }
+}
+
+void CallLowering::handleSRetStores(MachineIRBuilder &MIRBuilder, Type *RetTy,
+                                    ArrayRef<Register> VRegs,
+                                    Register DemoteReg) const {
+  MachineFunction &MF = MIRBuilder.getMF();
+  MachineRegisterInfo &MRI = MF.getRegInfo();
+  const DataLayout &DL = MF.getDataLayout();
+
+  SmallVector<EVT, 4> SplitVTs;
+  SmallVector<uint64_t, 4> Offsets;
+  ComputeValueVTs(*TLI, DL, RetTy, SplitVTs, &Offsets, 0);
+
+  assert(VRegs.size() == SplitVTs.size());
+
+  unsigned NumValues = SplitVTs.size();
+  Align BaseAlign = DL.getPrefTypeAlign(RetTy);
+  unsigned AS = DL.getAllocaAddrSpace();
+  LLT OffsetLLTy =
+      getLLTForType(*DL.getIntPtrType(RetTy->getPointerTo(AS)), DL);
+
+  MachinePointerInfo PtrInfo(AS);
+
+  for (unsigned I = 0; I < NumValues; ++I) {
+    Register Addr;
+    MIRBuilder.materializePtrAdd(Addr, DemoteReg, OffsetLLTy, Offsets[I]);
+    auto MMO = MF.getMachineMemOperand(PtrInfo, MachineMemOperand::MOStore,
+                                       MRI.getType(VRegs[I]).getSizeInBytes(),
+                                       commonAlignment(BaseAlign, Offsets[I]));
+    MIRBuilder.buildStore(VRegs[I], Addr, *MMO);
+  }
+}
+
+void CallLowering::insertSRetIncomingArgument(
+    const Function &F, SmallVectorImpl<ArgInfo> &SplitArgs, Register &DemoteReg,
+    MachineRegisterInfo &MRI, const DataLayout &DL) const {
+  unsigned AS = DL.getAllocaAddrSpace();
+  DemoteReg = MRI.createGenericVirtualRegister(
+      LLT::pointer(AS, DL.getPointerSizeInBits(AS)));
+
+  Type *PtrTy = PointerType::get(F.getReturnType(), AS);
+
+  SmallVector<EVT, 1> ValueVTs;
+  ComputeValueVTs(*TLI, DL, PtrTy, ValueVTs);
+
+  // NOTE: Assume that a pointer won't get split into more than one VT.
+  assert(ValueVTs.size() == 1);
+
+  ArgInfo DemoteArg(DemoteReg, ValueVTs[0].getTypeForEVT(PtrTy->getContext()));
+  setArgFlags(DemoteArg, AttributeList::ReturnIndex, DL, F);
+  DemoteArg.Flags[0].setSRet();
+  SplitArgs.insert(SplitArgs.begin(), DemoteArg);
+}
+
+void CallLowering::insertSRetOutgoingArgument(MachineIRBuilder &MIRBuilder,
+                                              const CallBase &CB,
+                                              CallLoweringInfo &Info) const {
+  const DataLayout &DL = MIRBuilder.getDataLayout();
+  Type *RetTy = CB.getType();
+  unsigned AS = DL.getAllocaAddrSpace();
+  LLT FramePtrTy = LLT::pointer(AS, DL.getPointerSizeInBits(AS));
+
+  int FI = MIRBuilder.getMF().getFrameInfo().CreateStackObject(
+      DL.getTypeAllocSize(RetTy), DL.getPrefTypeAlign(RetTy), false);
+
+  Register DemoteReg = MIRBuilder.buildFrameIndex(FramePtrTy, FI).getReg(0);
+  ArgInfo DemoteArg(DemoteReg, PointerType::get(RetTy, AS));
+  setArgFlags(DemoteArg, AttributeList::ReturnIndex, DL, CB);
+  DemoteArg.Flags[0].setSRet();
+
+  Info.OrigArgs.insert(Info.OrigArgs.begin(), DemoteArg);
+  Info.DemoteStackIndex = FI;
+  Info.DemoteRegister = DemoteReg;
+}
+
+bool CallLowering::checkReturn(CCState &CCInfo,
+                               SmallVectorImpl<BaseArgInfo> &Outs,
+                               CCAssignFn *Fn) const {
+  for (unsigned I = 0, E = Outs.size(); I < E; ++I) {
+    MVT VT = MVT::getVT(Outs[I].Ty);
+    if (Fn(I, VT, VT, CCValAssign::Full, Outs[I].Flags[0], CCInfo))
+      return false;
+  }
+  return true;
+}
+
+void CallLowering::getReturnInfo(CallingConv::ID CallConv, Type *RetTy,
+                                 AttributeList Attrs,
+                                 SmallVectorImpl<BaseArgInfo> &Outs,
+                                 const DataLayout &DL) const {
+  LLVMContext &Context = RetTy->getContext();
+  ISD::ArgFlagsTy Flags = ISD::ArgFlagsTy();
+
+  SmallVector<EVT, 4> SplitVTs;
+  ComputeValueVTs(*TLI, DL, RetTy, SplitVTs);
+  addArgFlagsFromAttributes(Flags, Attrs, AttributeList::ReturnIndex);
+
+  for (EVT VT : SplitVTs) {
+    unsigned NumParts =
+        TLI->getNumRegistersForCallingConv(Context, CallConv, VT);
+    MVT RegVT = TLI->getRegisterTypeForCallingConv(Context, CallConv, VT);
+    Type *PartTy = EVT(RegVT).getTypeForEVT(Context);
+
+    for (unsigned I = 0; I < NumParts; ++I) {
+      Outs.emplace_back(PartTy, Flags);
+    }
+  }
+}
+
+bool CallLowering::checkReturnTypeForCallConv(MachineFunction &MF) const {
+  const auto &F = MF.getFunction();
+  Type *ReturnType = F.getReturnType();
+  CallingConv::ID CallConv = F.getCallingConv();
+
+  SmallVector<BaseArgInfo, 4> SplitArgs;
+  getReturnInfo(CallConv, ReturnType, F.getAttributes(), SplitArgs,
+                MF.getDataLayout());
+  return canLowerReturn(MF, CallConv, SplitArgs, F.isVarArg(),
+                        ReturnType->getContext());
+}
+
 bool CallLowering::analyzeArgInfo(CCState &CCState,
                                   SmallVectorImpl<ArgInfo> &Args,
                                   CCAssignFn &AssignFnFixed,
                                   CCAssignFn &AssignFnVarArg) const {
   for (unsigned i = 0, e = Args.size(); i < e; ++i) {
     MVT VT = MVT::getVT(Args[i].Ty);
     CCAssignFn &Fn = Args[i].IsFixed ? AssignFnFixed : AssignFnVarArg;
     if (Fn(i, VT, VT, CCValAssign::Full, Args[i].Flags[0], CCState)) {

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

bool IRTranslator::translateRet(const User &U, MachineIRBuilder &MIRBuilder) {
   if (CLI->supportSwiftError() && SwiftError.getFunctionArg()) {
     SwiftErrorVReg = SwiftError.getOrCreateVRegUseAt(
         &RI, &MIRBuilder.getMBB(), SwiftError.getFunctionArg());
   }
 
   // The target may mess up with the insertion point, but
   // this is not important as a return is the last instruction
   // of the block anyway.
-  return CLI->lowerReturn(MIRBuilder, Ret, VRegs, SwiftErrorVReg);
+  return CLI->lowerReturn(MIRBuilder, Ret, VRegs, FuncInfo, SwiftErrorVReg);
 }
 
 void IRTranslator::emitBranchForMergedCondition(
     const Value *Cond, MachineBasicBlock *TBB, MachineBasicBlock *FBB,
     MachineBasicBlock *CurBB, MachineBasicBlock *SwitchBB,
     BranchProbability TProb, BranchProbability FProb, bool InvertCond) {
   // If the leaf of the tree is a comparison, merge the condition into
   // the caseblock.
bool IRTranslator::runOnMachineFunction(MachineFunction &CurMF) {
   TM.resetTargetOptions(F);
   EnableOpts = OptLevel != CodeGenOpt::None && !skipFunction(F);
   FuncInfo.MF = MF;
   if (EnableOpts)
     FuncInfo.BPI = &getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
   else
     FuncInfo.BPI = nullptr;
 
+  FuncInfo.CanLowerReturn = CLI->checkReturnTypeForCallConv(*MF);
+
   const auto &TLI = *MF->getSubtarget().getTargetLowering();
 
   SL = std::make_unique<GISelSwitchLowering>(this, FuncInfo);
   SL->init(TLI, TM, *DL);
 
 
 
   assert(PendingPHIs.empty() && "stale PHIs");
for (const Argument &Arg: F.args()) {
     VRegArgs.push_back(VRegs);
 
     if (Arg.hasSwiftErrorAttr()) {
       assert(VRegs.size() == 1 && "Too many vregs for Swift error");
       SwiftError.setCurrentVReg(EntryBB, SwiftError.getFunctionArg(), VRegs[0]);
     }
   }
 
-  if (!CLI->lowerFormalArguments(*EntryBuilder.get(), F, VRegArgs)) {
+  if (!CLI->lowerFormalArguments(*EntryBuilder.get(), F, VRegArgs, FuncInfo)) {
     OptimizationRemarkMissed R("gisel-irtranslator", "GISelFailure",
                                F.getSubprogram(), &F.getEntryBlock());
     R << "unable to lower arguments: " << ore::NV("Prototype", F.getType());
     reportTranslationError(*MF, *TPC, *ORE, R);
     return false;
   }
 
   // Need to visit defs before uses when translating instructions.

llvm/lib/Target/AArch64/GISel/AArch64CallLowering.h

 class MachineRegisterInfo;
 class Type;
 
 class AArch64CallLowering: public CallLowering {
 public:
   AArch64CallLowering(const AArch64TargetLowering &TLI);
 
   bool lowerReturn(MachineIRBuilder &MIRBuilder, const Value *Val,
-                   ArrayRef<Register> VRegs,
+                   ArrayRef<Register> VRegs, FunctionLoweringInfo &FLI,
                    Register SwiftErrorVReg) const override;
 
   bool fallBackToDAGISel(const Function &F) const override;
 
   bool lowerFormalArguments(MachineIRBuilder &MIRBuilder, const Function &F,
-                            ArrayRef<ArrayRef<Register>> VRegs) const override;
+                            ArrayRef<ArrayRef<Register>> VRegs,
+                            FunctionLoweringInfo &FLI) const override;
 
   bool lowerCall(MachineIRBuilder &MIRBuilder,
                  CallLoweringInfo &Info) const override;
 
   /// Returns true if the call can be lowered as a tail call.
   bool
   isEligibleForTailCallOptimization(MachineIRBuilder &MIRBuilder,
                                     CallLoweringInfo &Info,

llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp

void AArch64CallLowering::splitToValueTypes(
   }
 
   SplitArgs.back().Flags[0].setInConsecutiveRegsLast();
 }
 
 bool AArch64CallLowering::lowerReturn(MachineIRBuilder &MIRBuilder,
                                       const Value *Val,
                                       ArrayRef<Register> VRegs,
+                                      FunctionLoweringInfo &FLI,
                                       Register SwiftErrorVReg) const {
   auto MIB = MIRBuilder.buildInstrNoInsert(AArch64::RET_ReallyLR);
   assert(((Val && !VRegs.empty()) || (!Val && VRegs.empty())) &&
          "Return value without a vreg");
 
   bool Success = true;
   if (!VRegs.empty()) {
     MachineFunction &MF = MIRBuilder.getMF();
if (isa<ScalableVectorType>(F.getReturnType()))
     return true;
   return llvm::any_of(F.args(), [](const Argument &A) {
     return isa<ScalableVectorType>(A.getType());
   });
 }
 
 bool AArch64CallLowering::lowerFormalArguments(
     MachineIRBuilder &MIRBuilder, const Function &F,
-    ArrayRef<ArrayRef<Register>> VRegs) const {
+    ArrayRef<ArrayRef<Register>> VRegs, FunctionLoweringInfo &FLI) const {
   MachineFunction &MF = MIRBuilder.getMF();
   MachineBasicBlock &MBB = MIRBuilder.getMBB();
   MachineRegisterInfo &MRI = MF.getRegInfo();
   auto &DL = F.getParent()->getDataLayout();
 
   SmallVector<ArgInfo, 8> SplitArgs;
   unsigned i = 0;
   for (auto &Arg : F.args()) {

llvm/lib/Target/AMDGPU/AMDGPUCallLowering.h

class AMDGPUCallLowering final : public CallLowering {
 
   bool lowerReturnVal(MachineIRBuilder &B, const Value *Val,
                       ArrayRef<Register> VRegs, MachineInstrBuilder &Ret) const;
 
 public:
   AMDGPUCallLowering(const AMDGPUTargetLowering &TLI);
 
   bool lowerReturn(MachineIRBuilder &B, const Value *Val,
-                   ArrayRef<Register> VRegs) const override;
+                   ArrayRef<Register> VRegs,
+                   FunctionLoweringInfo &FLI) const override;
 
   bool lowerFormalArgumentsKernel(MachineIRBuilder &B, const Function &F,
                                   ArrayRef<ArrayRef<Register>> VRegs) const;
 
   bool lowerFormalArguments(MachineIRBuilder &B, const Function &F,
-                            ArrayRef<ArrayRef<Register>> VRegs) const override;
+                            ArrayRef<ArrayRef<Register>> VRegs,
+                            FunctionLoweringInfo &FLI) const override;
 
   bool passSpecialInputs(MachineIRBuilder &MIRBuilder,
                          CCState &CCInfo,
                          SmallVectorImpl<std::pair<MCRegister, Register>> &ArgRegs,
                          CallLoweringInfo &Info) const;
 
   bool lowerCall(MachineIRBuilder &MIRBuilder,
                  CallLoweringInfo &Info) const override;
 
   static CCAssignFn *CCAssignFnForCall(CallingConv::ID CC, bool IsVarArg);
   static CCAssignFn *CCAssignFnForReturn(CallingConv::ID CC, bool IsVarArg);
 };
 } // End of namespace llvm;
 #endif

llvm/lib/Target/AMDGPU/AMDGPUCallLowering.cpp

[&](ArrayRef<Register> Regs, Register SrcReg, LLT LLTy, LLT PartLLT,
                            LLTy, PartLLT);
     });
 
   CCAssignFn *AssignFn = TLI.CCAssignFnForReturn(CC, F.isVarArg());
   AMDGPUOutgoingValueHandler RetHandler(B, *MRI, Ret, AssignFn);
   return handleAssignments(B, SplitRetInfos, RetHandler);
 }
 
-bool AMDGPUCallLowering::lowerReturn(MachineIRBuilder &B,
-                                     const Value *Val,
-                                     ArrayRef<Register> VRegs) const {
+bool AMDGPUCallLowering::lowerReturn(MachineIRBuilder &B, const Value *Val,
+                                     ArrayRef<Register> VRegs,
+                                     FunctionLoweringInfo &FLI) const {
 
   MachineFunction &MF = B.getMF();
   MachineRegisterInfo &MRI = MF.getRegInfo();
   SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
   MFI->setIfReturnsVoid(!Val);
 
   assert(!Val == VRegs.empty() && "Return value without a vreg");
 
if (DstEltTy == PartLLT) {
     // Vector was split, and elements promoted to a wider type.
     LLT BVType = LLT::vector(LLTy.getNumElements(), PartLLT);
     auto BV = B.buildBuildVector(BVType, Regs);
     B.buildTrunc(OrigRegs[0], BV);
   }
 }
 
 bool AMDGPUCallLowering::lowerFormalArguments(
-    MachineIRBuilder &B, const Function &F,
-    ArrayRef<ArrayRef<Register>> VRegs) const {
+    MachineIRBuilder &B, const Function &F, ArrayRef<ArrayRef<Register>> VRegs,
+    FunctionLoweringInfo &FLI) const {
   CallingConv::ID CC = F.getCallingConv();
 
   // The infrastructure for normal calling convention lowering is essentially
   // useless for kernels. We want to avoid any kind of legalization or argument
   // splitting.
   if (CC == CallingConv::AMDGPU_KERNEL)
     return lowerFormalArgumentsKernel(B, F, VRegs);
 

llvm/lib/Target/ARM/ARMCallLowering.h

 class MachineIRBuilder;
 class Value;
 
 class ARMCallLowering : public CallLowering {
 public:
   ARMCallLowering(const ARMTargetLowering &TLI);
 
   bool lowerReturn(MachineIRBuilder &MIRBuilder, const Value *Val,
-                   ArrayRef<Register> VRegs) const override;
+                   ArrayRef<Register> VRegs,
+                   FunctionLoweringInfo &FLI) const override;
 
   bool lowerFormalArguments(MachineIRBuilder &MIRBuilder, const Function &F,
-                            ArrayRef<ArrayRef<Register>> VRegs) const override;
+                            ArrayRef<ArrayRef<Register>> VRegs,
+                            FunctionLoweringInfo &FLI) const override;
 
   bool lowerCall(MachineIRBuilder &MIRBuilder,
                  CallLoweringInfo &Info) const override;
 
 private:
   bool lowerReturnVal(MachineIRBuilder &MIRBuilder, const Value *Val,
                       ArrayRef<Register> VRegs,
                       MachineInstrBuilder &Ret) const;

llvm/lib/Target/ARM/ARMCallLowering.cpp

CCAssignFn *AssignFn =
       TLI.CCAssignFnForReturn(F.getCallingConv(), F.isVarArg());
 
   ARMOutgoingValueHandler RetHandler(MIRBuilder, MF.getRegInfo(), Ret,
                                      AssignFn);
   return handleAssignments(MIRBuilder, SplitRetInfos, RetHandler);
 }
 
 bool ARMCallLowering::lowerReturn(MachineIRBuilder &MIRBuilder,
-                                  const Value *Val,
-                                  ArrayRef<Register> VRegs) const {
+                                  const Value *Val, ArrayRef<Register> VRegs,
+                                  FunctionLoweringInfo &FLI) const {
   assert(!Val == VRegs.empty() && "Return value without a vreg");
 
   auto const &ST = MIRBuilder.getMF().getSubtarget<ARMSubtarget>();
   unsigned Opcode = ST.getReturnOpcode();
   auto Ret = MIRBuilder.buildInstrNoInsert(Opcode).add(predOps(ARMCC::AL));
 
   if (!lowerReturnVal(MIRBuilder, Val, VRegs, Ret))
     return false;
struct FormalArgHandler : public ARMIncomingValueHandler {
   void markPhysRegUsed(unsigned PhysReg) override {
     MIRBuilder.getMRI()->addLiveIn(PhysReg);
     MIRBuilder.getMBB().addLiveIn(PhysReg);
   }
 };
 
 } // end anonymous namespace
 
-bool ARMCallLowering::lowerFormalArguments(
-    MachineIRBuilder &MIRBuilder, const Function &F,
-    ArrayRef<ArrayRef<Register>> VRegs) const {
+bool ARMCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
+                                           const Function &F,
+                                           ArrayRef<ArrayRef<Register>> VRegs,
+                                           FunctionLoweringInfo &FLI) const {
   auto &TLI = *getTLI<ARMTargetLowering>();
   auto Subtarget = TLI.getSubtarget();
 
   if (Subtarget->isThumb1Only())
     return false;
 
   // Quick exit if there aren't any args
   if (F.arg_empty())

llvm/lib/Target/Mips/MipsCallLowering.h

virtual bool handleSplit(SmallVectorImpl<Register> &VRegs,
                              ArrayRef<CCValAssign> ArgLocs,
                              unsigned ArgLocsStartIndex, Register ArgsReg,
                              const EVT &VT) = 0;
   };
 
   MipsCallLowering(const MipsTargetLowering &TLI);
 
   bool lowerReturn(MachineIRBuilder &MIRBuilder, const Value *Val,
-                   ArrayRef<Register> VRegs) const override;
+                   ArrayRef<Register> VRegs,
+                   FunctionLoweringInfo &FLI) const override;
 
   bool lowerFormalArguments(MachineIRBuilder &MIRBuilder, const Function &F,
-                            ArrayRef<ArrayRef<Register>> VRegs) const override;
+                            ArrayRef<ArrayRef<Register>> VRegs,
+                            FunctionLoweringInfo &FLI) const override;
 
   bool lowerCall(MachineIRBuilder &MIRBuilder,
                  CallLoweringInfo &Info) const override;
 
 private:
   /// Based on registers available on target machine split or extend
   /// type if needed, also change pointer type to appropriate integer
   /// type.

llvm/lib/Target/Mips/MipsCallLowering.cpp

if (VA.isMemLoc())
                               VA.getLocMemOffset(), VA.getLocVT(), LocInfo);
     else
       ArgLocs[i] = CCValAssign::getReg(VA.getValNo(), VA.getValVT(),
                                        VA.getLocReg(), VA.getLocVT(), LocInfo);
   }
 }
 
 bool MipsCallLowering::lowerReturn(MachineIRBuilder &MIRBuilder,
-                                   const Value *Val,
-                                   ArrayRef<Register> VRegs) const {
+                                   const Value *Val, ArrayRef<Register> VRegs,
+                                   FunctionLoweringInfo &FLI) const {
 
   MachineInstrBuilder Ret = MIRBuilder.buildInstrNoInsert(Mips::RetRA);
 
   if (Val != nullptr && !isSupportedReturnType(Val->getType()))
     return false;
 
   if (!VRegs.empty()) {
     MachineFunction &MF = MIRBuilder.getMF();
if (!VRegs.empty()) {
     if (!RetHandler.handle(ArgLocs, RetInfos)) {
       return false;
     }
   }
   MIRBuilder.insertInstr(Ret);
   return true;
 }
 
-bool MipsCallLowering::lowerFormalArguments(
-    MachineIRBuilder &MIRBuilder, const Function &F,
-    ArrayRef<ArrayRef<Register>> VRegs) const {
+bool MipsCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
+                                            const Function &F,
+                                            ArrayRef<ArrayRef<Register>> VRegs,
+                                            FunctionLoweringInfo &FLI) const {
 
   // Quick exit if there aren't any args.
   if (F.arg_empty())
     return true;
 
   for (auto &Arg : F.args()) {
     if (!isSupportedArgumentType(Arg.getType()))
       return false;

llvm/lib/Target/PowerPC/GISel/PPCCallLowering.h

 
 class PPCTargetLowering;
 
 class PPCCallLowering : public CallLowering {
 public:
   PPCCallLowering(const PPCTargetLowering &TLI);
 
   bool lowerReturn(MachineIRBuilder &MIRBuilder, const Value *Val,
-                   ArrayRef<Register> VRegs,
+                   ArrayRef<Register> VRegs, FunctionLoweringInfo &FLI,
                    Register SwiftErrorVReg) const override;
   bool lowerFormalArguments(MachineIRBuilder &MIRBuilder, const Function &F,
-                            ArrayRef<ArrayRef<Register>> VRegs) const override;
+                            ArrayRef<ArrayRef<Register>> VRegs,
+                            FunctionLoweringInfo &FLI) const override;
   bool lowerCall(MachineIRBuilder &MIRBuilder,
                  CallLoweringInfo &Info) const override;
 };
 } // end namespace llvm
 
 #endif

llvm/lib/Target/PowerPC/GISel/PPCCallLowering.cpp

 
 using namespace llvm;
 
 PPCCallLowering::PPCCallLowering(const PPCTargetLowering &TLI)
     : CallLowering(&TLI) {}
 
 bool PPCCallLowering::lowerReturn(MachineIRBuilder &MIRBuilder,
                                   const Value *Val, ArrayRef<Register> VRegs,
+                                  FunctionLoweringInfo &FLI,
                                   Register SwiftErrorVReg) const {
   assert(((Val && !VRegs.empty()) || (!Val && VRegs.empty())) &&
          "Return value without a vreg");
   if (VRegs.size() > 0)
     return false;
 
   MIRBuilder.buildInstr(PPC::BLR8);
   return true;
 }
 
-bool PPCCallLowering::lowerFormalArguments(
-    MachineIRBuilder &MIRBuilder, const Function &F,
-    ArrayRef<ArrayRef<Register>> VRegs) const {
+bool PPCCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
+                                           const Function &F,
+                                           ArrayRef<ArrayRef<Register>> VRegs,
+                                           FunctionLoweringInfo &FLI) const {
 
   // If VRegs is empty, then there are no formal arguments to lower and thus can
   // always return true. If there are formal arguments, we currently do not
   // handle them and thus return false.
   return VRegs.empty();
 }
 
 bool PPCCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
                                 CallLoweringInfo &Info) const {
   return false;
 }

llvm/lib/Target/RISCV/RISCVCallLowering.h

 class RISCVTargetLowering;
 
 class RISCVCallLowering : public CallLowering {
 
 public:
   RISCVCallLowering(const RISCVTargetLowering &TLI);
 
   bool lowerReturn(MachineIRBuilder &MIRBuiler, const Value *Val,
-                   ArrayRef<Register> VRegs) const override;
+                   ArrayRef<Register> VRegs,
+                   FunctionLoweringInfo &FLI) const override;
 
   bool lowerFormalArguments(MachineIRBuilder &MIRBuilder, const Function &F,
-                            ArrayRef<ArrayRef<Register>> VRegs) const override;
+                            ArrayRef<ArrayRef<Register>> VRegs,
+                            FunctionLoweringInfo &FLI) const override;
 
   bool lowerCall(MachineIRBuilder &MIRBuilder,
                  CallLoweringInfo &Info) const override;
 };
 
 } // end namespace llvm
 
 #endif // LLVM_LIB_TARGET_RISCV_RISCVCALLLOWERING_H

llvm/lib/Target/RISCV/RISCVCallLowering.cpp

 #include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
 
 using namespace llvm;
 
 RISCVCallLowering::RISCVCallLowering(const RISCVTargetLowering &TLI)
     : CallLowering(&TLI) {}
 
 bool RISCVCallLowering::lowerReturn(MachineIRBuilder &MIRBuilder,
-                                    const Value *Val,
-                                    ArrayRef<Register> VRegs) const {
+                                    const Value *Val, ArrayRef<Register> VRegs,
+                                    FunctionLoweringInfo &FLI) const {
 
   MachineInstrBuilder Ret = MIRBuilder.buildInstrNoInsert(RISCV::PseudoRET);
 
   if (Val != nullptr) {
     return false;
   }
   MIRBuilder.insertInstr(Ret);
   return true;
 }
 
-bool RISCVCallLowering::lowerFormalArguments(
-    MachineIRBuilder &MIRBuilder, const Function &F,
-    ArrayRef<ArrayRef<Register>> VRegs) const {
+bool RISCVCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
+                                             const Function &F,
+                                             ArrayRef<ArrayRef<Register>> VRegs,
+                                             FunctionLoweringInfo &FLI) const {
 
   if (F.arg_empty())
     return true;
 
   return false;
 }
 
 bool RISCVCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
                                   CallLoweringInfo &Info) const {
   return false;
 }

llvm/lib/Target/X86/X86CallLowering.h

 class MachineRegisterInfo;
 class X86TargetLowering;
 
 class X86CallLowering : public CallLowering {
 public:
   X86CallLowering(const X86TargetLowering &TLI);
 
   bool lowerReturn(MachineIRBuilder &MIRBuilder, const Value *Val,
-                   ArrayRef<Register> VRegs) const override;
+                   ArrayRef<Register> VRegs,
+                   FunctionLoweringInfo &FLI) const override;
 
   bool lowerFormalArguments(MachineIRBuilder &MIRBuilder, const Function &F,
-                            ArrayRef<ArrayRef<Register>> VRegs) const override;
+                            ArrayRef<ArrayRef<Register>> VRegs,
+                            FunctionLoweringInfo &FLI) const override;
 
   bool lowerCall(MachineIRBuilder &MIRBuilder,
                  CallLoweringInfo &Info) const override;
 
 private:
   /// A function of this type is used to perform value split action.
   using SplitArgTy = std::function<void(ArrayRef<Register>)>;
 

llvm/lib/Target/X86/X86CallLowering.cpp

protected:
   uint64_t StackSize = 0;
   const DataLayout &DL;
   const X86Subtarget &STI;
   unsigned NumXMMRegs = 0;
 };
 
 } // end anonymous namespace
 
-bool X86CallLowering::lowerReturn(
-    MachineIRBuilder &MIRBuilder, const Value *Val,
-    ArrayRef<Register> VRegs) const {
+bool X86CallLowering::lowerReturn(MachineIRBuilder &MIRBuilder,
+                                  const Value *Val, ArrayRef<Register> VRegs,
+                                  FunctionLoweringInfo &FLI) const {
   assert(((Val && !VRegs.empty()) || (!Val && VRegs.empty())) &&
          "Return value without a vreg");
   auto MIB = MIRBuilder.buildInstrNoInsert(X86::RET).addImm(0);
 
   if (!VRegs.empty()) {
     MachineFunction &MF = MIRBuilder.getMF();
     const Function &F = MF.getFunction();
     MachineRegisterInfo &MRI = MF.getRegInfo();
struct CallReturnHandler : public X86IncomingValueHandler {
   }
 
 protected:
   MachineInstrBuilder &MIB;
 };
 
 } // end anonymous namespace
 
-bool X86CallLowering::lowerFormalArguments(
-    MachineIRBuilder &MIRBuilder, const Function &F,
-    ArrayRef<ArrayRef<Register>> VRegs) const {
+bool X86CallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
+                                           const Function &F,
+                                           ArrayRef<ArrayRef<Register>> VRegs,
+                                           FunctionLoweringInfo &FLI) const {
   if (F.arg_empty())
     return true;
 
   // TODO: handle variadic function
   if (F.isVarArg())
     return false;
 
   MachineFunction &MF = MIRBuilder.getMF();

llvm/tools/llvm-exegesis/lib/Assembler.cpp

 //===-- Assembler.cpp -------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "Assembler.h"
 
 #include "SnippetRepetitor.h"
 #include "Target.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/CodeGen/FunctionLoweringInfo.h"
 #include "llvm/CodeGen/GlobalISel/CallLowering.h"
 #include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/TargetInstrInfo.h"
 #include "llvm/CodeGen/TargetPassConfig.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"

 }
 
 void BasicBlockFiller::addInstructions(ArrayRef<MCInst> Insts,
                                        const DebugLoc &DL) {
   for (const MCInst &Inst : Insts)
     addInstruction(Inst, DL);
 }
 
 void BasicBlockFiller::addReturn(const DebugLoc &DL) {
   // Insert the return code.
   const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
   if (TII->getReturnOpcode() < TII->getNumOpcodes()) {
     BuildMI(MBB, DL, TII->get(TII->getReturnOpcode()));
   } else {
     MachineIRBuilder MIB(MF);
     MIB.setMBB(*MBB);
-    MF.getSubtarget().getCallLowering()->lowerReturn(MIB, nullptr, {});
+
+    FunctionLoweringInfo FuncInfo;
+    FuncInfo.CanLowerReturn = true;
+    MF.getSubtarget().getCallLowering()->lowerReturn(MIB, nullptr, {},
+                                                     FuncInfo);
   }
 }
 
 FunctionFiller::FunctionFiller(MachineFunction &MF,
                                std::vector<unsigned> RegistersSetUp)
     : MF(MF), MCII(MF.getTarget().getMCInstrInfo()), Entry(addBasicBlock()),
       RegistersSetUp(std::move(RegistersSetUp)) {}
 
 BasicBlockFiller FunctionFiller::addBasicBlock() {
   MachineBasicBlock *MBB = MF.CreateMachineBasicBlock();