1 //===----- CGCUDANV.cpp - Interface to NVIDIA CUDA Runtime ----------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This provides a class for CUDA code generation targeting the NVIDIA CUDA
10 // runtime library.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "CGCUDARuntime.h"
15 #include "CodeGenFunction.h"
16 #include "CodeGenModule.h"
17 #include "clang/AST/Decl.h"
18 #include "clang/Basic/Cuda.h"
19 #include "clang/CodeGen/CodeGenABITypes.h"
20 #include "clang/CodeGen/ConstantInitBuilder.h"
21 #include "llvm/IR/BasicBlock.h"
22 #include "llvm/IR/Constants.h"
23 #include "llvm/IR/DerivedTypes.h"
24 #include "llvm/Support/Format.h"
25 
26 using namespace clang;
27 using namespace CodeGen;
28 
29 namespace {
30 constexpr unsigned CudaFatMagic = 0x466243b1;
31 constexpr unsigned HIPFatMagic = 0x48495046; // "HIPF"
32 
33 class CGNVCUDARuntime : public CGCUDARuntime {
34 
35 private:
36   llvm::IntegerType *IntTy, *SizeTy;
37   llvm::Type *VoidTy;
38   llvm::PointerType *CharPtrTy, *VoidPtrTy, *VoidPtrPtrTy;
39 
40   /// Convenience reference to LLVM Context
41   llvm::LLVMContext &Context;
42   /// Convenience reference to the current module
43   llvm::Module &TheModule;
44   /// Keeps track of kernel launch stubs emitted in this module
45   struct KernelInfo {
46     llvm::Function *Kernel;
47     const Decl *D;
48   };
49   llvm::SmallVector<KernelInfo, 16> EmittedKernels;
50   struct VarInfo {
51     llvm::GlobalVariable *Var;
52     const VarDecl *D;
53     unsigned Flag;
54   };
55   llvm::SmallVector<VarInfo, 16> DeviceVars;
56   /// Keeps track of variable containing handle of GPU binary. Populated by
57   /// ModuleCtorFunction() and used to create corresponding cleanup calls in
58   /// ModuleDtorFunction()
59   llvm::GlobalVariable *GpuBinaryHandle = nullptr;
60   /// Whether we generate relocatable device code.
61   bool RelocatableDeviceCode;
62   /// Mangle context for device.
63   std::unique_ptr<MangleContext> DeviceMC;
64 
65   llvm::FunctionCallee getSetupArgumentFn() const;
66   llvm::FunctionCallee getLaunchFn() const;
67 
68   llvm::FunctionType *getRegisterGlobalsFnTy() const;
69   llvm::FunctionType *getCallbackFnTy() const;
70   llvm::FunctionType *getRegisterLinkedBinaryFnTy() const;
71   std::string addPrefixToName(StringRef FuncName) const;
72   std::string addUnderscoredPrefixToName(StringRef FuncName) const;
73 
74   /// Creates a function to register all kernel stubs generated in this module.
75   llvm::Function *makeRegisterGlobalsFn();
76 
77   /// Helper function that generates a constant string and returns a pointer to
78   /// the start of the string.  The result of this function can be used anywhere
79   /// where the C code specifies const char*.
80   llvm::Constant *makeConstantString(const std::string &Str,
81                                      const std::string &Name = "",
82                                      const std::string &SectionName = "",
83                                      unsigned Alignment = 0) {
84     llvm::Constant *Zeros[] = {llvm::ConstantInt::get(SizeTy, 0),
85                                llvm::ConstantInt::get(SizeTy, 0)};
86     auto ConstStr = CGM.GetAddrOfConstantCString(Str, Name.c_str());
87     llvm::GlobalVariable *GV =
88         cast<llvm::GlobalVariable>(ConstStr.getPointer());
89     if (!SectionName.empty()) {
90       GV->setSection(SectionName);
91       // Mark the address as used which make sure that this section isn't
92       // merged and we will really have it in the object file.
93       GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::None);
94     }
95     if (Alignment)
96       GV->setAlignment(Alignment);
97 
98     return llvm::ConstantExpr::getGetElementPtr(ConstStr.getElementType(),
99                                                 ConstStr.getPointer(), Zeros);
100   }
101 
102   /// Helper function that generates an empty dummy function returning void.
103   llvm::Function *makeDummyFunction(llvm::FunctionType *FnTy) {
104     assert(FnTy->getReturnType()->isVoidTy() &&
105            "Can only generate dummy functions returning void!");
106     llvm::Function *DummyFunc = llvm::Function::Create(
107         FnTy, llvm::GlobalValue::InternalLinkage, "dummy", &TheModule);
108 
109     llvm::BasicBlock *DummyBlock =
110         llvm::BasicBlock::Create(Context, "", DummyFunc);
111     CGBuilderTy FuncBuilder(CGM, Context);
112     FuncBuilder.SetInsertPoint(DummyBlock);
113     FuncBuilder.CreateRetVoid();
114 
115     return DummyFunc;
116   }
117 
118   void emitDeviceStubBodyLegacy(CodeGenFunction &CGF, FunctionArgList &Args);
119   void emitDeviceStubBodyNew(CodeGenFunction &CGF, FunctionArgList &Args);
120   std::string getDeviceSideName(const Decl *ND);
121 
122 public:
123   CGNVCUDARuntime(CodeGenModule &CGM);
124 
125   void emitDeviceStub(CodeGenFunction &CGF, FunctionArgList &Args) override;
126   void registerDeviceVar(const VarDecl *VD, llvm::GlobalVariable &Var,
127                          unsigned Flags) override {
128     DeviceVars.push_back({&Var, VD, Flags});
129   }
130 
131   /// Creates module constructor function
132   llvm::Function *makeModuleCtorFunction() override;
133   /// Creates module destructor function
134   llvm::Function *makeModuleDtorFunction() override;
135 };
136 
137 }
138 
139 std::string CGNVCUDARuntime::addPrefixToName(StringRef FuncName) const {
140   if (CGM.getLangOpts().HIP)
141     return ((Twine("hip") + Twine(FuncName)).str());
142   return ((Twine("cuda") + Twine(FuncName)).str());
143 }
144 std::string
145 CGNVCUDARuntime::addUnderscoredPrefixToName(StringRef FuncName) const {
146   if (CGM.getLangOpts().HIP)
147     return ((Twine("__hip") + Twine(FuncName)).str());
148   return ((Twine("__cuda") + Twine(FuncName)).str());
149 }
150 
151 CGNVCUDARuntime::CGNVCUDARuntime(CodeGenModule &CGM)
152     : CGCUDARuntime(CGM), Context(CGM.getLLVMContext()),
153       TheModule(CGM.getModule()),
154       RelocatableDeviceCode(CGM.getLangOpts().GPURelocatableDeviceCode),
155       DeviceMC(CGM.getContext().createMangleContext(
156           CGM.getContext().getAuxTargetInfo())) {
157   CodeGen::CodeGenTypes &Types = CGM.getTypes();
158   ASTContext &Ctx = CGM.getContext();
159 
160   IntTy = CGM.IntTy;
161   SizeTy = CGM.SizeTy;
162   VoidTy = CGM.VoidTy;
163 
164   CharPtrTy = llvm::PointerType::getUnqual(Types.ConvertType(Ctx.CharTy));
165   VoidPtrTy = cast<llvm::PointerType>(Types.ConvertType(Ctx.VoidPtrTy));
166   VoidPtrPtrTy = VoidPtrTy->getPointerTo();
167 }
168 
169 llvm::FunctionCallee CGNVCUDARuntime::getSetupArgumentFn() const {
170   // cudaError_t cudaSetupArgument(void *, size_t, size_t)
171   llvm::Type *Params[] = {VoidPtrTy, SizeTy, SizeTy};
172   return CGM.CreateRuntimeFunction(
173       llvm::FunctionType::get(IntTy, Params, false),
174       addPrefixToName("SetupArgument"));
175 }
176 
177 llvm::FunctionCallee CGNVCUDARuntime::getLaunchFn() const {
178   if (CGM.getLangOpts().HIP) {
179     // hipError_t hipLaunchByPtr(char *);
180     return CGM.CreateRuntimeFunction(
181         llvm::FunctionType::get(IntTy, CharPtrTy, false), "hipLaunchByPtr");
182   } else {
183     // cudaError_t cudaLaunch(char *);
184     return CGM.CreateRuntimeFunction(
185         llvm::FunctionType::get(IntTy, CharPtrTy, false), "cudaLaunch");
186   }
187 }
188 
189 llvm::FunctionType *CGNVCUDARuntime::getRegisterGlobalsFnTy() const {
190   return llvm::FunctionType::get(VoidTy, VoidPtrPtrTy, false);
191 }
192 
193 llvm::FunctionType *CGNVCUDARuntime::getCallbackFnTy() const {
194   return llvm::FunctionType::get(VoidTy, VoidPtrTy, false);
195 }
196 
197 llvm::FunctionType *CGNVCUDARuntime::getRegisterLinkedBinaryFnTy() const {
198   auto CallbackFnTy = getCallbackFnTy();
199   auto RegisterGlobalsFnTy = getRegisterGlobalsFnTy();
200   llvm::Type *Params[] = {RegisterGlobalsFnTy->getPointerTo(), VoidPtrTy,
201                           VoidPtrTy, CallbackFnTy->getPointerTo()};
202   return llvm::FunctionType::get(VoidTy, Params, false);
203 }
204 
205 std::string CGNVCUDARuntime::getDeviceSideName(const Decl *D) {
206   auto *ND = cast<const NamedDecl>(D);
207   std::string DeviceSideName;
208   if (DeviceMC->shouldMangleDeclName(ND)) {
209     SmallString<256> Buffer;
210     llvm::raw_svector_ostream Out(Buffer);
211     DeviceMC->mangleName(ND, Out);
212     DeviceSideName = Out.str();
213   } else
214     DeviceSideName = ND->getIdentifier()->getName();
215   return DeviceSideName;
216 }
217 
218 void CGNVCUDARuntime::emitDeviceStub(CodeGenFunction &CGF,
219                                      FunctionArgList &Args) {
220   assert(getDeviceSideName(CGF.CurFuncDecl) == CGF.CurFn->getName() ||
221          getDeviceSideName(CGF.CurFuncDecl) + ".stub" == CGF.CurFn->getName() ||
222          CGF.CGM.getContext().getTargetInfo().getCXXABI() !=
223              CGF.CGM.getContext().getAuxTargetInfo()->getCXXABI());
224 
225   EmittedKernels.push_back({CGF.CurFn, CGF.CurFuncDecl});
226   if (CudaFeatureEnabled(CGM.getTarget().getSDKVersion(),
227                          CudaFeature::CUDA_USES_NEW_LAUNCH))
228     emitDeviceStubBodyNew(CGF, Args);
229   else
230     emitDeviceStubBodyLegacy(CGF, Args);
231 }
232 
233 // CUDA 9.0+ uses new way to launch kernels. Parameters are packed in a local
234 // array and kernels are launched using cudaLaunchKernel().
235 void CGNVCUDARuntime::emitDeviceStubBodyNew(CodeGenFunction &CGF,
236                                             FunctionArgList &Args) {
237   // Build the shadow stack entry at the very start of the function.
238 
239   // Calculate amount of space we will need for all arguments.  If we have no
240   // args, allocate a single pointer so we still have a valid pointer to the
241   // argument array that we can pass to runtime, even if it will be unused.
242   Address KernelArgs = CGF.CreateTempAlloca(
243       VoidPtrTy, CharUnits::fromQuantity(16), "kernel_args",
244       llvm::ConstantInt::get(SizeTy, std::max<size_t>(1, Args.size())));
245   // Store pointers to the arguments in a locally allocated launch_args.
246   for (unsigned i = 0; i < Args.size(); ++i) {
247     llvm::Value* VarPtr = CGF.GetAddrOfLocalVar(Args[i]).getPointer();
248     llvm::Value *VoidVarPtr = CGF.Builder.CreatePointerCast(VarPtr, VoidPtrTy);
249     CGF.Builder.CreateDefaultAlignedStore(
250         VoidVarPtr, CGF.Builder.CreateConstGEP1_32(KernelArgs.getPointer(), i));
251   }
252 
253   llvm::BasicBlock *EndBlock = CGF.createBasicBlock("setup.end");
254 
255   // Lookup cudaLaunchKernel function.
256   // cudaError_t cudaLaunchKernel(const void *func, dim3 gridDim, dim3 blockDim,
257   //                              void **args, size_t sharedMem,
258   //                              cudaStream_t stream);
259   TranslationUnitDecl *TUDecl = CGM.getContext().getTranslationUnitDecl();
260   DeclContext *DC = TranslationUnitDecl::castToDeclContext(TUDecl);
261   IdentifierInfo &cudaLaunchKernelII =
262       CGM.getContext().Idents.get("cudaLaunchKernel");
263   FunctionDecl *cudaLaunchKernelFD = nullptr;
264   for (const auto &Result : DC->lookup(&cudaLaunchKernelII)) {
265     if (FunctionDecl *FD = dyn_cast<FunctionDecl>(Result))
266       cudaLaunchKernelFD = FD;
267   }
268 
269   if (cudaLaunchKernelFD == nullptr) {
270     CGM.Error(CGF.CurFuncDecl->getLocation(),
271               "Can't find declaration for cudaLaunchKernel()");
272     return;
273   }
274   // Create temporary dim3 grid_dim, block_dim.
275   ParmVarDecl *GridDimParam = cudaLaunchKernelFD->getParamDecl(1);
276   QualType Dim3Ty = GridDimParam->getType();
277   Address GridDim =
278       CGF.CreateMemTemp(Dim3Ty, CharUnits::fromQuantity(8), "grid_dim");
279   Address BlockDim =
280       CGF.CreateMemTemp(Dim3Ty, CharUnits::fromQuantity(8), "block_dim");
281   Address ShmemSize =
282       CGF.CreateTempAlloca(SizeTy, CGM.getSizeAlign(), "shmem_size");
283   Address Stream =
284       CGF.CreateTempAlloca(VoidPtrTy, CGM.getPointerAlign(), "stream");
285   llvm::FunctionCallee cudaPopConfigFn = CGM.CreateRuntimeFunction(
286       llvm::FunctionType::get(IntTy,
287                               {/*gridDim=*/GridDim.getType(),
288                                /*blockDim=*/BlockDim.getType(),
289                                /*ShmemSize=*/ShmemSize.getType(),
290                                /*Stream=*/Stream.getType()},
291                               /*isVarArg=*/false),
292       "__cudaPopCallConfiguration");
293 
294   CGF.EmitRuntimeCallOrInvoke(cudaPopConfigFn,
295                               {GridDim.getPointer(), BlockDim.getPointer(),
296                                ShmemSize.getPointer(), Stream.getPointer()});
297 
298   // Emit the call to cudaLaunch
299   llvm::Value *Kernel = CGF.Builder.CreatePointerCast(CGF.CurFn, VoidPtrTy);
300   CallArgList LaunchKernelArgs;
301   LaunchKernelArgs.add(RValue::get(Kernel),
302                        cudaLaunchKernelFD->getParamDecl(0)->getType());
303   LaunchKernelArgs.add(RValue::getAggregate(GridDim), Dim3Ty);
304   LaunchKernelArgs.add(RValue::getAggregate(BlockDim), Dim3Ty);
305   LaunchKernelArgs.add(RValue::get(KernelArgs.getPointer()),
306                        cudaLaunchKernelFD->getParamDecl(3)->getType());
307   LaunchKernelArgs.add(RValue::get(CGF.Builder.CreateLoad(ShmemSize)),
308                        cudaLaunchKernelFD->getParamDecl(4)->getType());
309   LaunchKernelArgs.add(RValue::get(CGF.Builder.CreateLoad(Stream)),
310                        cudaLaunchKernelFD->getParamDecl(5)->getType());
311 
312   QualType QT = cudaLaunchKernelFD->getType();
313   QualType CQT = QT.getCanonicalType();
314   llvm::Type *Ty = CGM.getTypes().ConvertType(CQT);
315   llvm::FunctionType *FTy = dyn_cast<llvm::FunctionType>(Ty);
316 
317   const CGFunctionInfo &FI =
318       CGM.getTypes().arrangeFunctionDeclaration(cudaLaunchKernelFD);
319   llvm::FunctionCallee cudaLaunchKernelFn =
320       CGM.CreateRuntimeFunction(FTy, "cudaLaunchKernel");
321   CGF.EmitCall(FI, CGCallee::forDirect(cudaLaunchKernelFn), ReturnValueSlot(),
322                LaunchKernelArgs);
323   CGF.EmitBranch(EndBlock);
324 
325   CGF.EmitBlock(EndBlock);
326 }
327 
328 void CGNVCUDARuntime::emitDeviceStubBodyLegacy(CodeGenFunction &CGF,
329                                                FunctionArgList &Args) {
330   // Emit a call to cudaSetupArgument for each arg in Args.
331   llvm::FunctionCallee cudaSetupArgFn = getSetupArgumentFn();
332   llvm::BasicBlock *EndBlock = CGF.createBasicBlock("setup.end");
333   CharUnits Offset = CharUnits::Zero();
334   for (const VarDecl *A : Args) {
335     CharUnits TyWidth, TyAlign;
336     std::tie(TyWidth, TyAlign) =
337         CGM.getContext().getTypeInfoInChars(A->getType());
338     Offset = Offset.alignTo(TyAlign);
339     llvm::Value *Args[] = {
340         CGF.Builder.CreatePointerCast(CGF.GetAddrOfLocalVar(A).getPointer(),
341                                       VoidPtrTy),
342         llvm::ConstantInt::get(SizeTy, TyWidth.getQuantity()),
343         llvm::ConstantInt::get(SizeTy, Offset.getQuantity()),
344     };
345     llvm::CallBase *CB = CGF.EmitRuntimeCallOrInvoke(cudaSetupArgFn, Args);
346     llvm::Constant *Zero = llvm::ConstantInt::get(IntTy, 0);
347     llvm::Value *CBZero = CGF.Builder.CreateICmpEQ(CB, Zero);
348     llvm::BasicBlock *NextBlock = CGF.createBasicBlock("setup.next");
349     CGF.Builder.CreateCondBr(CBZero, NextBlock, EndBlock);
350     CGF.EmitBlock(NextBlock);
351     Offset += TyWidth;
352   }
353 
354   // Emit the call to cudaLaunch
355   llvm::FunctionCallee cudaLaunchFn = getLaunchFn();
356   llvm::Value *Arg = CGF.Builder.CreatePointerCast(CGF.CurFn, CharPtrTy);
357   CGF.EmitRuntimeCallOrInvoke(cudaLaunchFn, Arg);
358   CGF.EmitBranch(EndBlock);
359 
360   CGF.EmitBlock(EndBlock);
361 }
362 
363 /// Creates a function that sets up state on the host side for CUDA objects that
364 /// have a presence on both the host and device sides. Specifically, registers
365 /// the host side of kernel functions and device global variables with the CUDA
366 /// runtime.
367 /// \code
368 /// void __cuda_register_globals(void** GpuBinaryHandle) {
369 ///    __cudaRegisterFunction(GpuBinaryHandle,Kernel0,...);
370 ///    ...
371 ///    __cudaRegisterFunction(GpuBinaryHandle,KernelM,...);
372 ///    __cudaRegisterVar(GpuBinaryHandle, GlobalVar0, ...);
373 ///    ...
374 ///    __cudaRegisterVar(GpuBinaryHandle, GlobalVarN, ...);
375 /// }
376 /// \endcode
377 llvm::Function *CGNVCUDARuntime::makeRegisterGlobalsFn() {
378   // No need to register anything
379   if (EmittedKernels.empty() && DeviceVars.empty())
380     return nullptr;
381 
382   llvm::Function *RegisterKernelsFunc = llvm::Function::Create(
383       getRegisterGlobalsFnTy(), llvm::GlobalValue::InternalLinkage,
384       addUnderscoredPrefixToName("_register_globals"), &TheModule);
385   llvm::BasicBlock *EntryBB =
386       llvm::BasicBlock::Create(Context, "entry", RegisterKernelsFunc);
387   CGBuilderTy Builder(CGM, Context);
388   Builder.SetInsertPoint(EntryBB);
389 
390   // void __cudaRegisterFunction(void **, const char *, char *, const char *,
391   //                             int, uint3*, uint3*, dim3*, dim3*, int*)
392   llvm::Type *RegisterFuncParams[] = {
393       VoidPtrPtrTy, CharPtrTy, CharPtrTy, CharPtrTy, IntTy,
394       VoidPtrTy,    VoidPtrTy, VoidPtrTy, VoidPtrTy, IntTy->getPointerTo()};
395   llvm::FunctionCallee RegisterFunc = CGM.CreateRuntimeFunction(
396       llvm::FunctionType::get(IntTy, RegisterFuncParams, false),
397       addUnderscoredPrefixToName("RegisterFunction"));
398 
399   // Extract GpuBinaryHandle passed as the first argument passed to
400   // __cuda_register_globals() and generate __cudaRegisterFunction() call for
401   // each emitted kernel.
402   llvm::Argument &GpuBinaryHandlePtr = *RegisterKernelsFunc->arg_begin();
403   for (auto &&I : EmittedKernels) {
404     llvm::Constant *KernelName = makeConstantString(getDeviceSideName(I.D));
405     llvm::Constant *NullPtr = llvm::ConstantPointerNull::get(VoidPtrTy);
406     llvm::Value *Args[] = {
407         &GpuBinaryHandlePtr,
408         Builder.CreateBitCast(I.Kernel, VoidPtrTy),
409         KernelName,
410         KernelName,
411         llvm::ConstantInt::get(IntTy, -1),
412         NullPtr,
413         NullPtr,
414         NullPtr,
415         NullPtr,
416         llvm::ConstantPointerNull::get(IntTy->getPointerTo())};
417     Builder.CreateCall(RegisterFunc, Args);
418   }
419 
420   // void __cudaRegisterVar(void **, char *, char *, const char *,
421   //                        int, int, int, int)
422   llvm::Type *RegisterVarParams[] = {VoidPtrPtrTy, CharPtrTy, CharPtrTy,
423                                      CharPtrTy,    IntTy,     IntTy,
424                                      IntTy,        IntTy};
425   llvm::FunctionCallee RegisterVar = CGM.CreateRuntimeFunction(
426       llvm::FunctionType::get(IntTy, RegisterVarParams, false),
427       addUnderscoredPrefixToName("RegisterVar"));
428   for (auto &&Info : DeviceVars) {
429     llvm::GlobalVariable *Var = Info.Var;
430     unsigned Flags = Info.Flag;
431     llvm::Constant *VarName = makeConstantString(getDeviceSideName(Info.D));
432     uint64_t VarSize =
433         CGM.getDataLayout().getTypeAllocSize(Var->getValueType());
434     llvm::Value *Args[] = {
435         &GpuBinaryHandlePtr,
436         Builder.CreateBitCast(Var, VoidPtrTy),
437         VarName,
438         VarName,
439         llvm::ConstantInt::get(IntTy, (Flags & ExternDeviceVar) ? 1 : 0),
440         llvm::ConstantInt::get(IntTy, VarSize),
441         llvm::ConstantInt::get(IntTy, (Flags & ConstantDeviceVar) ? 1 : 0),
442         llvm::ConstantInt::get(IntTy, 0)};
443     Builder.CreateCall(RegisterVar, Args);
444   }
445 
446   Builder.CreateRetVoid();
447   return RegisterKernelsFunc;
448 }
449 
450 /// Creates a global constructor function for the module:
451 ///
452 /// For CUDA:
453 /// \code
454 /// void __cuda_module_ctor(void*) {
455 ///     Handle = __cudaRegisterFatBinary(GpuBinaryBlob);
456 ///     __cuda_register_globals(Handle);
457 /// }
458 /// \endcode
459 ///
460 /// For HIP:
461 /// \code
462 /// void __hip_module_ctor(void*) {
463 ///     if (__hip_gpubin_handle == 0) {
464 ///         __hip_gpubin_handle  = __hipRegisterFatBinary(GpuBinaryBlob);
465 ///         __hip_register_globals(__hip_gpubin_handle);
466 ///     }
467 /// }
468 /// \endcode
469 llvm::Function *CGNVCUDARuntime::makeModuleCtorFunction() {
470   bool IsHIP = CGM.getLangOpts().HIP;
471   // No need to generate ctors/dtors if there is no GPU binary.
472   StringRef CudaGpuBinaryFileName = CGM.getCodeGenOpts().CudaGpuBinaryFileName;
473   if (CudaGpuBinaryFileName.empty() && !IsHIP)
474     return nullptr;
475 
476   // void __{cuda|hip}_register_globals(void* handle);
477   llvm::Function *RegisterGlobalsFunc = makeRegisterGlobalsFn();
478   // We always need a function to pass in as callback. Create a dummy
479   // implementation if we don't need to register anything.
480   if (RelocatableDeviceCode && !RegisterGlobalsFunc)
481     RegisterGlobalsFunc = makeDummyFunction(getRegisterGlobalsFnTy());
482 
483   // void ** __{cuda|hip}RegisterFatBinary(void *);
484   llvm::FunctionCallee RegisterFatbinFunc = CGM.CreateRuntimeFunction(
485       llvm::FunctionType::get(VoidPtrPtrTy, VoidPtrTy, false),
486       addUnderscoredPrefixToName("RegisterFatBinary"));
487   // struct { int magic, int version, void * gpu_binary, void * dont_care };
488   llvm::StructType *FatbinWrapperTy =
489       llvm::StructType::get(IntTy, IntTy, VoidPtrTy, VoidPtrTy);
490 
491   // Register GPU binary with the CUDA runtime, store returned handle in a
492   // global variable and save a reference in GpuBinaryHandle to be cleaned up
493   // in destructor on exit. Then associate all known kernels with the GPU binary
494   // handle so CUDA runtime can figure out what to call on the GPU side.
495   std::unique_ptr<llvm::MemoryBuffer> CudaGpuBinary = nullptr;
496   if (!CudaGpuBinaryFileName.empty()) {
497     llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> CudaGpuBinaryOrErr =
498         llvm::MemoryBuffer::getFileOrSTDIN(CudaGpuBinaryFileName);
499     if (std::error_code EC = CudaGpuBinaryOrErr.getError()) {
500       CGM.getDiags().Report(diag::err_cannot_open_file)
501           << CudaGpuBinaryFileName << EC.message();
502       return nullptr;
503     }
504     CudaGpuBinary = std::move(CudaGpuBinaryOrErr.get());
505   }
506 
507   llvm::Function *ModuleCtorFunc = llvm::Function::Create(
508       llvm::FunctionType::get(VoidTy, VoidPtrTy, false),
509       llvm::GlobalValue::InternalLinkage,
510       addUnderscoredPrefixToName("_module_ctor"), &TheModule);
511   llvm::BasicBlock *CtorEntryBB =
512       llvm::BasicBlock::Create(Context, "entry", ModuleCtorFunc);
513   CGBuilderTy CtorBuilder(CGM, Context);
514 
515   CtorBuilder.SetInsertPoint(CtorEntryBB);
516 
517   const char *FatbinConstantName;
518   const char *FatbinSectionName;
519   const char *ModuleIDSectionName;
520   StringRef ModuleIDPrefix;
521   llvm::Constant *FatBinStr;
522   unsigned FatMagic;
523   if (IsHIP) {
524     FatbinConstantName = ".hip_fatbin";
525     FatbinSectionName = ".hipFatBinSegment";
526 
527     ModuleIDSectionName = "__hip_module_id";
528     ModuleIDPrefix = "__hip_";
529 
530     if (CudaGpuBinary) {
531       // If fatbin is available from early finalization, create a string
532       // literal containing the fat binary loaded from the given file.
533       FatBinStr = makeConstantString(CudaGpuBinary->getBuffer(), "",
534                                      FatbinConstantName, 8);
535     } else {
536       // If fatbin is not available, create an external symbol
537       // __hip_fatbin in section .hip_fatbin. The external symbol is supposed
538       // to contain the fat binary but will be populated somewhere else,
539       // e.g. by lld through link script.
540       FatBinStr = new llvm::GlobalVariable(
541         CGM.getModule(), CGM.Int8Ty,
542         /*isConstant=*/true, llvm::GlobalValue::ExternalLinkage, nullptr,
543         "__hip_fatbin", nullptr,
544         llvm::GlobalVariable::NotThreadLocal);
545       cast<llvm::GlobalVariable>(FatBinStr)->setSection(FatbinConstantName);
546     }
547 
548     FatMagic = HIPFatMagic;
549   } else {
550     if (RelocatableDeviceCode)
551       FatbinConstantName = CGM.getTriple().isMacOSX()
552                                ? "__NV_CUDA,__nv_relfatbin"
553                                : "__nv_relfatbin";
554     else
555       FatbinConstantName =
556           CGM.getTriple().isMacOSX() ? "__NV_CUDA,__nv_fatbin" : ".nv_fatbin";
557     // NVIDIA's cuobjdump looks for fatbins in this section.
558     FatbinSectionName =
559         CGM.getTriple().isMacOSX() ? "__NV_CUDA,__fatbin" : ".nvFatBinSegment";
560 
561     ModuleIDSectionName = CGM.getTriple().isMacOSX()
562                               ? "__NV_CUDA,__nv_module_id"
563                               : "__nv_module_id";
564     ModuleIDPrefix = "__nv_";
565 
566     // For CUDA, create a string literal containing the fat binary loaded from
567     // the given file.
568     FatBinStr = makeConstantString(CudaGpuBinary->getBuffer(), "",
569                                    FatbinConstantName, 8);
570     FatMagic = CudaFatMagic;
571   }
572 
573   // Create initialized wrapper structure that points to the loaded GPU binary
574   ConstantInitBuilder Builder(CGM);
575   auto Values = Builder.beginStruct(FatbinWrapperTy);
576   // Fatbin wrapper magic.
577   Values.addInt(IntTy, FatMagic);
578   // Fatbin version.
579   Values.addInt(IntTy, 1);
580   // Data.
581   Values.add(FatBinStr);
582   // Unused in fatbin v1.
583   Values.add(llvm::ConstantPointerNull::get(VoidPtrTy));
584   llvm::GlobalVariable *FatbinWrapper = Values.finishAndCreateGlobal(
585       addUnderscoredPrefixToName("_fatbin_wrapper"), CGM.getPointerAlign(),
586       /*constant*/ true);
587   FatbinWrapper->setSection(FatbinSectionName);
588 
589   // There is only one HIP fat binary per linked module, however there are
590   // multiple constructor functions. Make sure the fat binary is registered
591   // only once. The constructor functions are executed by the dynamic loader
592   // before the program gains control. The dynamic loader cannot execute the
593   // constructor functions concurrently since doing that would not guarantee
594   // thread safety of the loaded program. Therefore we can assume sequential
595   // execution of constructor functions here.
596   if (IsHIP) {
597     auto Linkage = CudaGpuBinary ? llvm::GlobalValue::InternalLinkage :
598         llvm::GlobalValue::LinkOnceAnyLinkage;
599     llvm::BasicBlock *IfBlock =
600         llvm::BasicBlock::Create(Context, "if", ModuleCtorFunc);
601     llvm::BasicBlock *ExitBlock =
602         llvm::BasicBlock::Create(Context, "exit", ModuleCtorFunc);
603     // The name, size, and initialization pattern of this variable is part
604     // of HIP ABI.
605     GpuBinaryHandle = new llvm::GlobalVariable(
606         TheModule, VoidPtrPtrTy, /*isConstant=*/false,
607         Linkage,
608         /*Initializer=*/llvm::ConstantPointerNull::get(VoidPtrPtrTy),
609         "__hip_gpubin_handle");
610     GpuBinaryHandle->setAlignment(CGM.getPointerAlign().getQuantity());
611     // Prevent the weak symbol in different shared libraries being merged.
612     if (Linkage != llvm::GlobalValue::InternalLinkage)
613       GpuBinaryHandle->setVisibility(llvm::GlobalValue::HiddenVisibility);
614     Address GpuBinaryAddr(
615         GpuBinaryHandle,
616         CharUnits::fromQuantity(GpuBinaryHandle->getAlignment()));
617     {
618       auto HandleValue = CtorBuilder.CreateLoad(GpuBinaryAddr);
619       llvm::Constant *Zero =
620           llvm::Constant::getNullValue(HandleValue->getType());
621       llvm::Value *EQZero = CtorBuilder.CreateICmpEQ(HandleValue, Zero);
622       CtorBuilder.CreateCondBr(EQZero, IfBlock, ExitBlock);
623     }
624     {
625       CtorBuilder.SetInsertPoint(IfBlock);
626       // GpuBinaryHandle = __hipRegisterFatBinary(&FatbinWrapper);
627       llvm::CallInst *RegisterFatbinCall = CtorBuilder.CreateCall(
628           RegisterFatbinFunc,
629           CtorBuilder.CreateBitCast(FatbinWrapper, VoidPtrTy));
630       CtorBuilder.CreateStore(RegisterFatbinCall, GpuBinaryAddr);
631       CtorBuilder.CreateBr(ExitBlock);
632     }
633     {
634       CtorBuilder.SetInsertPoint(ExitBlock);
635       // Call __hip_register_globals(GpuBinaryHandle);
636       if (RegisterGlobalsFunc) {
637         auto HandleValue = CtorBuilder.CreateLoad(GpuBinaryAddr);
638         CtorBuilder.CreateCall(RegisterGlobalsFunc, HandleValue);
639       }
640     }
641   } else if (!RelocatableDeviceCode) {
642     // Register binary with CUDA runtime. This is substantially different in
643     // default mode vs. separate compilation!
644     // GpuBinaryHandle = __cudaRegisterFatBinary(&FatbinWrapper);
645     llvm::CallInst *RegisterFatbinCall = CtorBuilder.CreateCall(
646         RegisterFatbinFunc,
647         CtorBuilder.CreateBitCast(FatbinWrapper, VoidPtrTy));
648     GpuBinaryHandle = new llvm::GlobalVariable(
649         TheModule, VoidPtrPtrTy, false, llvm::GlobalValue::InternalLinkage,
650         llvm::ConstantPointerNull::get(VoidPtrPtrTy), "__cuda_gpubin_handle");
651     GpuBinaryHandle->setAlignment(CGM.getPointerAlign().getQuantity());
652     CtorBuilder.CreateAlignedStore(RegisterFatbinCall, GpuBinaryHandle,
653                                    CGM.getPointerAlign());
654 
655     // Call __cuda_register_globals(GpuBinaryHandle);
656     if (RegisterGlobalsFunc)
657       CtorBuilder.CreateCall(RegisterGlobalsFunc, RegisterFatbinCall);
658 
659     // Call __cudaRegisterFatBinaryEnd(Handle) if this CUDA version needs it.
660     if (CudaFeatureEnabled(CGM.getTarget().getSDKVersion(),
661                            CudaFeature::CUDA_USES_FATBIN_REGISTER_END)) {
662       // void __cudaRegisterFatBinaryEnd(void **);
663       llvm::FunctionCallee RegisterFatbinEndFunc = CGM.CreateRuntimeFunction(
664           llvm::FunctionType::get(VoidTy, VoidPtrPtrTy, false),
665           "__cudaRegisterFatBinaryEnd");
666       CtorBuilder.CreateCall(RegisterFatbinEndFunc, RegisterFatbinCall);
667     }
668   } else {
669     // Generate a unique module ID.
670     SmallString<64> ModuleID;
671     llvm::raw_svector_ostream OS(ModuleID);
672     OS << ModuleIDPrefix << llvm::format("%" PRIx64, FatbinWrapper->getGUID());
673     llvm::Constant *ModuleIDConstant =
674         makeConstantString(ModuleID.str(), "", ModuleIDSectionName, 32);
675 
676     // Create an alias for the FatbinWrapper that nvcc will look for.
677     llvm::GlobalAlias::create(llvm::GlobalValue::ExternalLinkage,
678                               Twine("__fatbinwrap") + ModuleID, FatbinWrapper);
679 
680     // void __cudaRegisterLinkedBinary%ModuleID%(void (*)(void *), void *,
681     // void *, void (*)(void **))
682     SmallString<128> RegisterLinkedBinaryName("__cudaRegisterLinkedBinary");
683     RegisterLinkedBinaryName += ModuleID;
684     llvm::FunctionCallee RegisterLinkedBinaryFunc = CGM.CreateRuntimeFunction(
685         getRegisterLinkedBinaryFnTy(), RegisterLinkedBinaryName);
686 
687     assert(RegisterGlobalsFunc && "Expecting at least dummy function!");
688     llvm::Value *Args[] = {RegisterGlobalsFunc,
689                            CtorBuilder.CreateBitCast(FatbinWrapper, VoidPtrTy),
690                            ModuleIDConstant,
691                            makeDummyFunction(getCallbackFnTy())};
692     CtorBuilder.CreateCall(RegisterLinkedBinaryFunc, Args);
693   }
694 
695   // Create destructor and register it with atexit() the way NVCC does it. Doing
696   // it during regular destructor phase worked in CUDA before 9.2 but results in
697   // double-free in 9.2.
698   if (llvm::Function *CleanupFn = makeModuleDtorFunction()) {
699     // extern "C" int atexit(void (*f)(void));
700     llvm::FunctionType *AtExitTy =
701         llvm::FunctionType::get(IntTy, CleanupFn->getType(), false);
702     llvm::FunctionCallee AtExitFunc =
703         CGM.CreateRuntimeFunction(AtExitTy, "atexit", llvm::AttributeList(),
704                                   /*Local=*/true);
705     CtorBuilder.CreateCall(AtExitFunc, CleanupFn);
706   }
707 
708   CtorBuilder.CreateRetVoid();
709   return ModuleCtorFunc;
710 }
711 
712 /// Creates a global destructor function that unregisters the GPU code blob
713 /// registered by constructor.
714 ///
715 /// For CUDA:
716 /// \code
717 /// void __cuda_module_dtor(void*) {
718 ///     __cudaUnregisterFatBinary(Handle);
719 /// }
720 /// \endcode
721 ///
722 /// For HIP:
723 /// \code
724 /// void __hip_module_dtor(void*) {
725 ///     if (__hip_gpubin_handle) {
726 ///         __hipUnregisterFatBinary(__hip_gpubin_handle);
727 ///         __hip_gpubin_handle = 0;
728 ///     }
729 /// }
730 /// \endcode
731 llvm::Function *CGNVCUDARuntime::makeModuleDtorFunction() {
732   // No need for destructor if we don't have a handle to unregister.
733   if (!GpuBinaryHandle)
734     return nullptr;
735 
736   // void __cudaUnregisterFatBinary(void ** handle);
737   llvm::FunctionCallee UnregisterFatbinFunc = CGM.CreateRuntimeFunction(
738       llvm::FunctionType::get(VoidTy, VoidPtrPtrTy, false),
739       addUnderscoredPrefixToName("UnregisterFatBinary"));
740 
741   llvm::Function *ModuleDtorFunc = llvm::Function::Create(
742       llvm::FunctionType::get(VoidTy, VoidPtrTy, false),
743       llvm::GlobalValue::InternalLinkage,
744       addUnderscoredPrefixToName("_module_dtor"), &TheModule);
745 
746   llvm::BasicBlock *DtorEntryBB =
747       llvm::BasicBlock::Create(Context, "entry", ModuleDtorFunc);
748   CGBuilderTy DtorBuilder(CGM, Context);
749   DtorBuilder.SetInsertPoint(DtorEntryBB);
750 
751   Address GpuBinaryAddr(GpuBinaryHandle, CharUnits::fromQuantity(
752                                              GpuBinaryHandle->getAlignment()));
753   auto HandleValue = DtorBuilder.CreateLoad(GpuBinaryAddr);
754   // There is only one HIP fat binary per linked module, however there are
755   // multiple destructor functions. Make sure the fat binary is unregistered
756   // only once.
757   if (CGM.getLangOpts().HIP) {
758     llvm::BasicBlock *IfBlock =
759         llvm::BasicBlock::Create(Context, "if", ModuleDtorFunc);
760     llvm::BasicBlock *ExitBlock =
761         llvm::BasicBlock::Create(Context, "exit", ModuleDtorFunc);
762     llvm::Constant *Zero = llvm::Constant::getNullValue(HandleValue->getType());
763     llvm::Value *NEZero = DtorBuilder.CreateICmpNE(HandleValue, Zero);
764     DtorBuilder.CreateCondBr(NEZero, IfBlock, ExitBlock);
765 
766     DtorBuilder.SetInsertPoint(IfBlock);
767     DtorBuilder.CreateCall(UnregisterFatbinFunc, HandleValue);
768     DtorBuilder.CreateStore(Zero, GpuBinaryAddr);
769     DtorBuilder.CreateBr(ExitBlock);
770 
771     DtorBuilder.SetInsertPoint(ExitBlock);
772   } else {
773     DtorBuilder.CreateCall(UnregisterFatbinFunc, HandleValue);
774   }
775   DtorBuilder.CreateRetVoid();
776   return ModuleDtorFunc;
777 }
778 
779 CGCUDARuntime *CodeGen::CreateNVCUDARuntime(CodeGenModule &CGM) {
780   return new CGNVCUDARuntime(CGM);
781 }
782