[GlobalISel][AArch64] Tail call libcalls.

llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h

@@ -288,11 +288,14 @@ class LegalizerHelper {
 
   // Implements floating-point environment read/write via library function call.
   LegalizeResult createGetStateLibcall(MachineIRBuilder &MIRBuilder,
-                                       MachineInstr &MI);
+                                       MachineInstr &MI,
+                                       LostDebugLocObserver &LocObserver);
   LegalizeResult createSetStateLibcall(MachineIRBuilder &MIRBuilder,
-                                       MachineInstr &MI);
+                                       MachineInstr &MI,
+                                       LostDebugLocObserver &LocObserver);
   LegalizeResult createResetStateLibcall(MachineIRBuilder &MIRBuilder,
-                                         MachineInstr &MI);
+                                         MachineInstr &MI,
+                                         LostDebugLocObserver &LocObserver);
 
 public:
   /// Return the alignment to use for a stack temporary object with the given
@@ -440,13 +443,15 @@ class LegalizerHelper {
 LegalizerHelper::LegalizeResult
 createLibcall(MachineIRBuilder &MIRBuilder, const char *Name,
               const CallLowering::ArgInfo &Result,
-              ArrayRef<CallLowering::ArgInfo> Args, CallingConv::ID CC);
+              ArrayRef<CallLowering::ArgInfo> Args, CallingConv::ID CC,
+              LostDebugLocObserver &LocObserver, MachineInstr *MI = nullptr);
 
 /// Helper function that creates the given libcall.
 LegalizerHelper::LegalizeResult
 createLibcall(MachineIRBuilder &MIRBuilder, RTLIB::Libcall Libcall,
               const CallLowering::ArgInfo &Result,
-              ArrayRef<CallLowering::ArgInfo> Args);
+              ArrayRef<CallLowering::ArgInfo> Args,
+              LostDebugLocObserver &LocObserver, MachineInstr *MI = nullptr);
 
 /// Create a libcall to memcpy et al.
 LegalizerHelper::LegalizeResult

llvm/include/llvm/CodeGen/GlobalISel/LegalizerInfo.h

@@ -35,6 +35,7 @@ extern cl::opt<bool> DisableGISelLegalityCheck;
 class MachineFunction;
 class raw_ostream;
 class LegalizerHelper;
+class LostDebugLocObserver;
 class MachineInstr;
 class MachineRegisterInfo;
 class MCInstrInfo;
@@ -1288,8 +1289,8 @@ class LegalizerInfo {
                        const MachineRegisterInfo &MRI) const;
 
   /// Called for instructions with the Custom LegalizationAction.
-  virtual bool legalizeCustom(LegalizerHelper &Helper,
-                              MachineInstr &MI) const {
+  virtual bool legalizeCustom(LegalizerHelper &Helper, MachineInstr &MI,
+                              LostDebugLocObserver &LocObserver) const {
     llvm_unreachable("must implement this if custom action is used");
   }
 

llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp

@@ -149,7 +149,8 @@ LegalizerHelper::legalizeInstrStep(MachineInstr &MI,
     return moreElementsVector(MI, Step.TypeIdx, Step.NewType);
   case Custom:
     LLVM_DEBUG(dbgs() << ".. Custom legalization\n");
-    return LI.legalizeCustom(*this, MI) ? Legalized : UnableToLegalize;
+    return LI.legalizeCustom(*this, MI, LocObserver) ? Legalized
+                                                     : UnableToLegalize;
   default:
     LLVM_DEBUG(dbgs() << ".. Unable to legalize\n");
     return UnableToLegalize;
@@ -567,7 +568,8 @@ static RTLIB::Libcall getRTLibDesc(unsigned Opcode, unsigned Size) {
 
 /// True if an instruction is in tail position in its caller. Intended for
 /// legalizing libcalls as tail calls when possible.
-static bool isLibCallInTailPosition(MachineInstr &MI,
+static bool isLibCallInTailPosition(const CallLowering::ArgInfo &Result,
+                                    MachineInstr &MI,
                                     const TargetInstrInfo &TII,
                                     MachineRegisterInfo &MRI) {
   MachineBasicBlock &MBB = *MI.getParent();
@@ -596,17 +598,12 @@ static bool isLibCallInTailPosition(MachineInstr &MI,
   //   RET_ReallyLR implicit $x0
   auto Next = next_nodbg(MI.getIterator(), MBB.instr_end());
   if (Next != MBB.instr_end() && Next->isCopy()) {
-    switch (MI.getOpcode()) {
-    default:
-      llvm_unreachable("unsupported opcode");
-    case TargetOpcode::G_BZERO:
+    if (MI.getOpcode() == TargetOpcode::G_BZERO)
       return false;
-    case TargetOpcode::G_MEMCPY:
-    case TargetOpcode::G_MEMMOVE:
-    case TargetOpcode::G_MEMSET:
-      break;
-    }
 
+    // For MEMCPY/MOMMOVE/MEMSET these will be the first use (the dst), as the
+    // mempy/etc routines return the same parameter. For other it will be the
+    // returned value.
     Register VReg = MI.getOperand(0).getReg();
     if (!VReg.isVirtual() || VReg != Next->getOperand(1).getReg())
       return false;
@@ -622,7 +619,7 @@ static bool isLibCallInTailPosition(MachineInstr &MI,
     if (Ret->getNumImplicitOperands() != 1)
       return false;
 
-    if (PReg != Ret->getOperand(0).getReg())
+    if (!Ret->getOperand(0).isReg() || PReg != Ret->getOperand(0).getReg())
       return false;
 
     // Skip over the COPY that we just validated.
@@ -639,42 +636,73 @@ LegalizerHelper::LegalizeResult
 llvm::createLibcall(MachineIRBuilder &MIRBuilder, const char *Name,
                     const CallLowering::ArgInfo &Result,
                     ArrayRef<CallLowering::ArgInfo> Args,
-                    const CallingConv::ID CC) {
+                    const CallingConv::ID CC, LostDebugLocObserver &LocObserver,
+                    MachineInstr *MI) {
   auto &CLI = *MIRBuilder.getMF().getSubtarget().getCallLowering();
 
   CallLowering::CallLoweringInfo Info;
   Info.CallConv = CC;
   Info.Callee = MachineOperand::CreateES(Name);
   Info.OrigRet = Result;
+  if (MI)
+    Info.IsTailCall =
+        (Result.Ty->isVoidTy() ||
+         Result.Ty == MIRBuilder.getMF().getFunction().getReturnType()) &&
+        isLibCallInTailPosition(Result, *MI, MIRBuilder.getTII(),
+                                *MIRBuilder.getMRI());
+
   std::copy(Args.begin(), Args.end(), std::back_inserter(Info.OrigArgs));
   if (!CLI.lowerCall(MIRBuilder, Info))
     return LegalizerHelper::UnableToLegalize;
 
+  if (MI && Info.LoweredTailCall) {
+    assert(Info.IsTailCall && "Lowered tail call when it wasn't a tail call?");
+
+    // Check debug locations before removing the return.
+    LocObserver.checkpoint(true);
+
+    // We must have a return following the call (or debug insts) to get past
+    // isLibCallInTailPosition.
+    do {
+      MachineInstr *Next = MI->getNextNode();
+      assert(Next &&
+             (Next->isCopy() || Next->isReturn() || Next->isDebugInstr()) &&
+             "Expected instr following MI to be return or debug inst?");
+      // We lowered a tail call, so the call is now the return from the block.
+      // Delete the old return.
+      Next->eraseFromParent();
+    } while (MI->getNextNode());
+
+    // We expect to lose the debug location from the return.
+    LocObserver.checkpoint(false);
+  }
   return LegalizerHelper::Legalized;
 }
 
 LegalizerHelper::LegalizeResult
 llvm::createLibcall(MachineIRBuilder &MIRBuilder, RTLIB::Libcall Libcall,
                     const CallLowering::ArgInfo &Result,
-                    ArrayRef<CallLowering::ArgInfo> Args) {
+                    ArrayRef<CallLowering::ArgInfo> Args,
+                    LostDebugLocObserver &LocObserver, MachineInstr *MI) {
   auto &TLI = *MIRBuilder.getMF().getSubtarget().getTargetLowering();
   const char *Name = TLI.getLibcallName(Libcall);
   const CallingConv::ID CC = TLI.getLibcallCallingConv(Libcall);
-  return createLibcall(MIRBuilder, Name, Result, Args, CC);
+  return createLibcall(MIRBuilder, Name, Result, Args, CC, LocObserver, MI);
 }
 
 // Useful for libcalls where all operands have the same type.
 static LegalizerHelper::LegalizeResult
 simpleLibcall(MachineInstr &MI, MachineIRBuilder &MIRBuilder, unsigned Size,
-              Type *OpType) {
+              Type *OpType, LostDebugLocObserver &LocObserver) {
   auto Libcall = getRTLibDesc(MI.getOpcode(), Size);
 
   // FIXME: What does the original arg index mean here?
   SmallVector<CallLowering::ArgInfo, 3> Args;
   for (const MachineOperand &MO : llvm::drop_begin(MI.operands()))
     Args.push_back({MO.getReg(), OpType, 0});
   return createLibcall(MIRBuilder, Libcall,
-                       {MI.getOperand(0).getReg(), OpType, 0}, Args);
+                       {MI.getOperand(0).getReg(), OpType, 0}, Args,
+                       LocObserver, &MI);
 }
 
 LegalizerHelper::LegalizeResult
@@ -733,8 +761,9 @@ llvm::createMemLibcall(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI,
   Info.CallConv = TLI.getLibcallCallingConv(RTLibcall);
   Info.Callee = MachineOperand::CreateES(Name);
   Info.OrigRet = CallLowering::ArgInfo({0}, Type::getVoidTy(Ctx), 0);
-  Info.IsTailCall = MI.getOperand(MI.getNumOperands() - 1).getImm() &&
-                    isLibCallInTailPosition(MI, MIRBuilder.getTII(), MRI);
+  Info.IsTailCall =
+      MI.getOperand(MI.getNumOperands() - 1).getImm() &&
+      isLibCallInTailPosition(Info.OrigRet, MI, MIRBuilder.getTII(), MRI);
 
   std::copy(Args.begin(), Args.end(), std::back_inserter(Info.OrigArgs));
   if (!CLI.lowerCall(MIRBuilder, Info))
@@ -789,11 +818,11 @@ static RTLIB::Libcall getConvRTLibDesc(unsigned Opcode, Type *ToType,
 
 static LegalizerHelper::LegalizeResult
 conversionLibcall(MachineInstr &MI, MachineIRBuilder &MIRBuilder, Type *ToType,
-                  Type *FromType) {
+                  Type *FromType, LostDebugLocObserver &LocObserver) {
   RTLIB::Libcall Libcall = getConvRTLibDesc(MI.getOpcode(), ToType, FromType);
-  return createLibcall(MIRBuilder, Libcall,
-                       {MI.getOperand(0).getReg(), ToType, 0},
-                       {{MI.getOperand(1).getReg(), FromType, 0}});
+  return createLibcall(
+      MIRBuilder, Libcall, {MI.getOperand(0).getReg(), ToType, 0},
+      {{MI.getOperand(1).getReg(), FromType, 0}}, LocObserver, &MI);
 }
 
 static RTLIB::Libcall
@@ -829,7 +858,8 @@ getStateLibraryFunctionFor(MachineInstr &MI, const TargetLowering &TLI) {
 //
 LegalizerHelper::LegalizeResult
 LegalizerHelper::createGetStateLibcall(MachineIRBuilder &MIRBuilder,
-                                       MachineInstr &MI) {
+                                       MachineInstr &MI,
+                                       LostDebugLocObserver &LocObserver) {
   const DataLayout &DL = MIRBuilder.getDataLayout();
   auto &MF = MIRBuilder.getMF();
   auto &MRI = *MIRBuilder.getMRI();
@@ -850,7 +880,8 @@ LegalizerHelper::createGetStateLibcall(MachineIRBuilder &MIRBuilder,
   auto Res =
       createLibcall(MIRBuilder, RTLibcall,
                     CallLowering::ArgInfo({0}, Type::getVoidTy(Ctx), 0),
-                    CallLowering::ArgInfo({Temp.getReg(0), StatePtrTy, 0}));
+                    CallLowering::ArgInfo({Temp.getReg(0), StatePtrTy, 0}),
+                    LocObserver, nullptr);
   if (Res != LegalizerHelper::Legalized)
     return Res;
 
@@ -867,7 +898,8 @@ LegalizerHelper::createGetStateLibcall(MachineIRBuilder &MIRBuilder,
 // content of memory region.
 LegalizerHelper::LegalizeResult
 LegalizerHelper::createSetStateLibcall(MachineIRBuilder &MIRBuilder,
-                                       MachineInstr &MI) {
+                                       MachineInstr &MI,
+                                       LostDebugLocObserver &LocObserver) {
   const DataLayout &DL = MIRBuilder.getDataLayout();
   auto &MF = MIRBuilder.getMF();
   auto &MRI = *MIRBuilder.getMRI();
@@ -892,7 +924,8 @@ LegalizerHelper::createSetStateLibcall(MachineIRBuilder &MIRBuilder,
   RTLIB::Libcall RTLibcall = getStateLibraryFunctionFor(MI, TLI);
   return createLibcall(MIRBuilder, RTLibcall,
                        CallLowering::ArgInfo({0}, Type::getVoidTy(Ctx), 0),
-                       CallLowering::ArgInfo({Temp.getReg(0), StatePtrTy, 0}));
+                       CallLowering::ArgInfo({Temp.getReg(0), StatePtrTy, 0}),
+                       LocObserver, nullptr);
 }
 
 // The function is used to legalize operations that set default environment
@@ -902,7 +935,8 @@ LegalizerHelper::createSetStateLibcall(MachineIRBuilder &MIRBuilder,
 // it is not true, the target must provide custom lowering.
 LegalizerHelper::LegalizeResult
 LegalizerHelper::createResetStateLibcall(MachineIRBuilder &MIRBuilder,
-                                         MachineInstr &MI) {
+                                         MachineInstr &MI,
+                                         LostDebugLocObserver &LocObserver) {
   const DataLayout &DL = MIRBuilder.getDataLayout();
   auto &MF = MIRBuilder.getMF();
   auto &Ctx = MF.getFunction().getContext();
@@ -919,7 +953,8 @@ LegalizerHelper::createResetStateLibcall(MachineIRBuilder &MIRBuilder,
   RTLIB::Libcall RTLibcall = getStateLibraryFunctionFor(MI, TLI);
   return createLibcall(MIRBuilder, RTLibcall,
                        CallLowering::ArgInfo({0}, Type::getVoidTy(Ctx), 0),
-                       CallLowering::ArgInfo({ Dest.getReg(), StatePtrTy, 0}));
+                       CallLowering::ArgInfo({Dest.getReg(), StatePtrTy, 0}),
+                       LocObserver, &MI);
 }
 
 LegalizerHelper::LegalizeResult
@@ -938,7 +973,7 @@ LegalizerHelper::libcall(MachineInstr &MI, LostDebugLocObserver &LocObserver) {
     LLT LLTy = MRI.getType(MI.getOperand(0).getReg());
     unsigned Size = LLTy.getSizeInBits();
     Type *HLTy = IntegerType::get(Ctx, Size);
-    auto Status = simpleLibcall(MI, MIRBuilder, Size, HLTy);
+    auto Status = simpleLibcall(MI, MIRBuilder, Size, HLTy, LocObserver);
     if (Status != Legalized)
       return Status;
     break;
@@ -974,7 +1009,7 @@ LegalizerHelper::libcall(MachineInstr &MI, LostDebugLocObserver &LocObserver) {
       LLVM_DEBUG(dbgs() << "No libcall available for type " << LLTy << ".\n");
       return UnableToLegalize;
     }
-    auto Status = simpleLibcall(MI, MIRBuilder, Size, HLTy);
+    auto Status = simpleLibcall(MI, MIRBuilder, Size, HLTy, LocObserver);
     if (Status != Legalized)
       return Status;
     break;
@@ -985,7 +1020,8 @@ LegalizerHelper::libcall(MachineInstr &MI, LostDebugLocObserver &LocObserver) {
     Type *ToTy = getFloatTypeForLLT(Ctx, MRI.getType(MI.getOperand(0).getReg()));
     if (!FromTy || !ToTy)
       return UnableToLegalize;
-    LegalizeResult Status = conversionLibcall(MI, MIRBuilder, ToTy, FromTy );
+    LegalizeResult Status =
+        conversionLibcall(MI, MIRBuilder, ToTy, FromTy, LocObserver);
     if (Status != Legalized)
       return Status;
     break;
@@ -1000,7 +1036,8 @@ LegalizerHelper::libcall(MachineInstr &MI, LostDebugLocObserver &LocObserver) {
     LegalizeResult Status = conversionLibcall(
         MI, MIRBuilder,
         ToSize == 32 ? Type::getInt32Ty(Ctx) : Type::getInt64Ty(Ctx),
-        FromSize == 64 ? Type::getDoubleTy(Ctx) : Type::getFloatTy(Ctx));
+        FromSize == 64 ? Type::getDoubleTy(Ctx) : Type::getFloatTy(Ctx),
+        LocObserver);
     if (Status != Legalized)
       return Status;
     break;
@@ -1015,7 +1052,8 @@ LegalizerHelper::libcall(MachineInstr &MI, LostDebugLocObserver &LocObserver) {
     LegalizeResult Status = conversionLibcall(
         MI, MIRBuilder,
         ToSize == 64 ? Type::getDoubleTy(Ctx) : Type::getFloatTy(Ctx),
-        FromSize == 32 ? Type::getInt32Ty(Ctx) : Type::getInt64Ty(Ctx));
+        FromSize == 32 ? Type::getInt32Ty(Ctx) : Type::getInt64Ty(Ctx),
+        LocObserver);
     if (Status != Legalized)
       return Status;
     break;
@@ -1032,19 +1070,20 @@ LegalizerHelper::libcall(MachineInstr &MI, LostDebugLocObserver &LocObserver) {
     return Result;
   }
   case TargetOpcode::G_GET_FPMODE: {
-    LegalizeResult Result = createGetStateLibcall(MIRBuilder, MI);
+    LegalizeResult Result = createGetStateLibcall(MIRBuilder, MI, LocObserver);
     if (Result != Legalized)
       return Result;
     break;
   }
   case TargetOpcode::G_SET_FPMODE: {
-    LegalizeResult Result = createSetStateLibcall(MIRBuilder, MI);
+    LegalizeResult Result = createSetStateLibcall(MIRBuilder, MI, LocObserver);
     if (Result != Legalized)
       return Result;
     break;
   }
   case TargetOpcode::G_RESET_FPMODE: {
-    LegalizeResult Result = createResetStateLibcall(MIRBuilder, MI);
+    LegalizeResult Result =
+        createResetStateLibcall(MIRBuilder, MI, LocObserver);
     if (Result != Legalized)
       return Result;
     break;

llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp

@@ -1133,8 +1133,9 @@ AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST)
   verify(*ST.getInstrInfo());
 }
 
-bool AArch64LegalizerInfo::legalizeCustom(LegalizerHelper &Helper,
-                                          MachineInstr &MI) const {
+bool AArch64LegalizerInfo::legalizeCustom(
+    LegalizerHelper &Helper, MachineInstr &MI,
+    LostDebugLocObserver &LocObserver) const {
   MachineIRBuilder &MIRBuilder = Helper.MIRBuilder;
   MachineRegisterInfo &MRI = *MIRBuilder.getMRI();
   GISelChangeObserver &Observer = Helper.Observer;

llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.h

@@ -28,7 +28,8 @@ class AArch64LegalizerInfo : public LegalizerInfo {
 public:
   AArch64LegalizerInfo(const AArch64Subtarget &ST);
 
-  bool legalizeCustom(LegalizerHelper &Helper, MachineInstr &MI) const override;
+  bool legalizeCustom(LegalizerHelper &Helper, MachineInstr &MI,
+                      LostDebugLocObserver &LocObserver) const override;
 
   bool legalizeIntrinsic(LegalizerHelper &Helper,
                          MachineInstr &MI) const override;

llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp

@@ -1996,8 +1996,9 @@ AMDGPULegalizerInfo::AMDGPULegalizerInfo(const GCNSubtarget &ST_,
   verify(*ST.getInstrInfo());
 }
 
-bool AMDGPULegalizerInfo::legalizeCustom(LegalizerHelper &Helper,
-                                         MachineInstr &MI) const {
+bool AMDGPULegalizerInfo::legalizeCustom(
+    LegalizerHelper &Helper, MachineInstr &MI,
+    LostDebugLocObserver &LocObserver) const {
   MachineIRBuilder &B = Helper.MIRBuilder;
   MachineRegisterInfo &MRI = *B.getMRI();
 

llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.h

@@ -35,7 +35,8 @@ class AMDGPULegalizerInfo final : public LegalizerInfo {
   AMDGPULegalizerInfo(const GCNSubtarget &ST,
                       const GCNTargetMachine &TM);
 
-  bool legalizeCustom(LegalizerHelper &Helper, MachineInstr &MI) const override;
+  bool legalizeCustom(LegalizerHelper &Helper, MachineInstr &MI,
+                      LostDebugLocObserver &LocObserver) const override;
 
   Register getSegmentAperture(unsigned AddrSpace,
                               MachineRegisterInfo &MRI,