• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 //===----- CGCUDANV.cpp - Interface to NVIDIA CUDA Runtime ----------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This provides a class for CUDA code generation targeting the NVIDIA CUDA
11 // runtime library.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "CGCUDARuntime.h"
16 #include "CodeGenFunction.h"
17 #include "CodeGenModule.h"
18 #include "clang/AST/Decl.h"
19 #include "llvm/IR/BasicBlock.h"
20 #include "llvm/IR/CallSite.h"
21 #include "llvm/IR/Constants.h"
22 #include "llvm/IR/DerivedTypes.h"
23 
24 using namespace clang;
25 using namespace CodeGen;
26 
27 namespace {
28 
29 class CGNVCUDARuntime : public CGCUDARuntime {
30 
31 private:
32   llvm::Type *IntTy, *SizeTy, *VoidTy;
33   llvm::PointerType *CharPtrTy, *VoidPtrTy, *VoidPtrPtrTy;
34 
35   /// Convenience reference to LLVM Context
36   llvm::LLVMContext &Context;
37   /// Convenience reference to the current module
38   llvm::Module &TheModule;
39   /// Keeps track of kernel launch stubs emitted in this module
40   llvm::SmallVector<llvm::Function *, 16> EmittedKernels;
41   llvm::SmallVector<std::pair<llvm::GlobalVariable *, unsigned>, 16> DeviceVars;
42   /// Keeps track of variables containing handles of GPU binaries. Populated by
43   /// ModuleCtorFunction() and used to create corresponding cleanup calls in
44   /// ModuleDtorFunction()
45   llvm::SmallVector<llvm::GlobalVariable *, 16> GpuBinaryHandles;
46 
47   llvm::Constant *getSetupArgumentFn() const;
48   llvm::Constant *getLaunchFn() const;
49 
50   /// Creates a function to register all kernel stubs generated in this module.
51   llvm::Function *makeRegisterGlobalsFn();
52 
53   /// Helper function that generates a constant string and returns a pointer to
54   /// the start of the string.  The result of this function can be used anywhere
55   /// where the C code specifies const char*.
makeConstantString(const std::string & Str,const std::string & Name="",unsigned Alignment=0)56   llvm::Constant *makeConstantString(const std::string &Str,
57                                      const std::string &Name = "",
58                                      unsigned Alignment = 0) {
59     llvm::Constant *Zeros[] = {llvm::ConstantInt::get(SizeTy, 0),
60                                llvm::ConstantInt::get(SizeTy, 0)};
61     auto ConstStr = CGM.GetAddrOfConstantCString(Str, Name.c_str());
62     return llvm::ConstantExpr::getGetElementPtr(ConstStr.getElementType(),
63                                                 ConstStr.getPointer(), Zeros);
64  }
65 
66   void emitDeviceStubBody(CodeGenFunction &CGF, FunctionArgList &Args);
67 
68 public:
69   CGNVCUDARuntime(CodeGenModule &CGM);
70 
71   void emitDeviceStub(CodeGenFunction &CGF, FunctionArgList &Args) override;
registerDeviceVar(llvm::GlobalVariable & Var,unsigned Flags)72   void registerDeviceVar(llvm::GlobalVariable &Var, unsigned Flags) override {
73     DeviceVars.push_back(std::make_pair(&Var, Flags));
74   }
75 
76   /// Creates module constructor function
77   llvm::Function *makeModuleCtorFunction() override;
78   /// Creates module destructor function
79   llvm::Function *makeModuleDtorFunction() override;
80 };
81 
82 }
83 
CGNVCUDARuntime(CodeGenModule & CGM)84 CGNVCUDARuntime::CGNVCUDARuntime(CodeGenModule &CGM)
85     : CGCUDARuntime(CGM), Context(CGM.getLLVMContext()),
86       TheModule(CGM.getModule()) {
87   CodeGen::CodeGenTypes &Types = CGM.getTypes();
88   ASTContext &Ctx = CGM.getContext();
89 
90   IntTy = Types.ConvertType(Ctx.IntTy);
91   SizeTy = Types.ConvertType(Ctx.getSizeType());
92   VoidTy = llvm::Type::getVoidTy(Context);
93 
94   CharPtrTy = llvm::PointerType::getUnqual(Types.ConvertType(Ctx.CharTy));
95   VoidPtrTy = cast<llvm::PointerType>(Types.ConvertType(Ctx.VoidPtrTy));
96   VoidPtrPtrTy = VoidPtrTy->getPointerTo();
97 }
98 
getSetupArgumentFn() const99 llvm::Constant *CGNVCUDARuntime::getSetupArgumentFn() const {
100   // cudaError_t cudaSetupArgument(void *, size_t, size_t)
101   llvm::Type *Params[] = {VoidPtrTy, SizeTy, SizeTy};
102   return CGM.CreateRuntimeFunction(llvm::FunctionType::get(IntTy,
103                                                            Params, false),
104                                    "cudaSetupArgument");
105 }
106 
getLaunchFn() const107 llvm::Constant *CGNVCUDARuntime::getLaunchFn() const {
108   // cudaError_t cudaLaunch(char *)
109   return CGM.CreateRuntimeFunction(
110       llvm::FunctionType::get(IntTy, CharPtrTy, false), "cudaLaunch");
111 }
112 
emitDeviceStub(CodeGenFunction & CGF,FunctionArgList & Args)113 void CGNVCUDARuntime::emitDeviceStub(CodeGenFunction &CGF,
114                                      FunctionArgList &Args) {
115   EmittedKernels.push_back(CGF.CurFn);
116   emitDeviceStubBody(CGF, Args);
117 }
118 
emitDeviceStubBody(CodeGenFunction & CGF,FunctionArgList & Args)119 void CGNVCUDARuntime::emitDeviceStubBody(CodeGenFunction &CGF,
120                                          FunctionArgList &Args) {
121   // Build the argument value list and the argument stack struct type.
122   SmallVector<llvm::Value *, 16> ArgValues;
123   std::vector<llvm::Type *> ArgTypes;
124   for (FunctionArgList::const_iterator I = Args.begin(), E = Args.end();
125        I != E; ++I) {
126     llvm::Value *V = CGF.GetAddrOfLocalVar(*I).getPointer();
127     ArgValues.push_back(V);
128     assert(isa<llvm::PointerType>(V->getType()) && "Arg type not PointerType");
129     ArgTypes.push_back(cast<llvm::PointerType>(V->getType())->getElementType());
130   }
131   llvm::StructType *ArgStackTy = llvm::StructType::get(Context, ArgTypes);
132 
133   llvm::BasicBlock *EndBlock = CGF.createBasicBlock("setup.end");
134 
135   // Emit the calls to cudaSetupArgument
136   llvm::Constant *cudaSetupArgFn = getSetupArgumentFn();
137   for (unsigned I = 0, E = Args.size(); I != E; ++I) {
138     llvm::Value *Args[3];
139     llvm::BasicBlock *NextBlock = CGF.createBasicBlock("setup.next");
140     Args[0] = CGF.Builder.CreatePointerCast(ArgValues[I], VoidPtrTy);
141     Args[1] = CGF.Builder.CreateIntCast(
142         llvm::ConstantExpr::getSizeOf(ArgTypes[I]),
143         SizeTy, false);
144     Args[2] = CGF.Builder.CreateIntCast(
145         llvm::ConstantExpr::getOffsetOf(ArgStackTy, I),
146         SizeTy, false);
147     llvm::CallSite CS = CGF.EmitRuntimeCallOrInvoke(cudaSetupArgFn, Args);
148     llvm::Constant *Zero = llvm::ConstantInt::get(IntTy, 0);
149     llvm::Value *CSZero = CGF.Builder.CreateICmpEQ(CS.getInstruction(), Zero);
150     CGF.Builder.CreateCondBr(CSZero, NextBlock, EndBlock);
151     CGF.EmitBlock(NextBlock);
152   }
153 
154   // Emit the call to cudaLaunch
155   llvm::Constant *cudaLaunchFn = getLaunchFn();
156   llvm::Value *Arg = CGF.Builder.CreatePointerCast(CGF.CurFn, CharPtrTy);
157   CGF.EmitRuntimeCallOrInvoke(cudaLaunchFn, Arg);
158   CGF.EmitBranch(EndBlock);
159 
160   CGF.EmitBlock(EndBlock);
161 }
162 
163 /// Creates a function that sets up state on the host side for CUDA objects that
164 /// have a presence on both the host and device sides. Specifically, registers
165 /// the host side of kernel functions and device global variables with the CUDA
166 /// runtime.
167 /// \code
168 /// void __cuda_register_globals(void** GpuBinaryHandle) {
169 ///    __cudaRegisterFunction(GpuBinaryHandle,Kernel0,...);
170 ///    ...
171 ///    __cudaRegisterFunction(GpuBinaryHandle,KernelM,...);
172 ///    __cudaRegisterVar(GpuBinaryHandle, GlobalVar0, ...);
173 ///    ...
174 ///    __cudaRegisterVar(GpuBinaryHandle, GlobalVarN, ...);
175 /// }
176 /// \endcode
makeRegisterGlobalsFn()177 llvm::Function *CGNVCUDARuntime::makeRegisterGlobalsFn() {
178   // No need to register anything
179   if (EmittedKernels.empty() && DeviceVars.empty())
180     return nullptr;
181 
182   llvm::Function *RegisterKernelsFunc = llvm::Function::Create(
183       llvm::FunctionType::get(VoidTy, VoidPtrPtrTy, false),
184       llvm::GlobalValue::InternalLinkage, "__cuda_register_globals", &TheModule);
185   llvm::BasicBlock *EntryBB =
186       llvm::BasicBlock::Create(Context, "entry", RegisterKernelsFunc);
187   CGBuilderTy Builder(CGM, Context);
188   Builder.SetInsertPoint(EntryBB);
189 
190   // void __cudaRegisterFunction(void **, const char *, char *, const char *,
191   //                             int, uint3*, uint3*, dim3*, dim3*, int*)
192   llvm::Type *RegisterFuncParams[] = {
193       VoidPtrPtrTy, CharPtrTy, CharPtrTy, CharPtrTy, IntTy,
194       VoidPtrTy,    VoidPtrTy, VoidPtrTy, VoidPtrTy, IntTy->getPointerTo()};
195   llvm::Constant *RegisterFunc = CGM.CreateRuntimeFunction(
196       llvm::FunctionType::get(IntTy, RegisterFuncParams, false),
197       "__cudaRegisterFunction");
198 
199   // Extract GpuBinaryHandle passed as the first argument passed to
200   // __cuda_register_globals() and generate __cudaRegisterFunction() call for
201   // each emitted kernel.
202   llvm::Argument &GpuBinaryHandlePtr = *RegisterKernelsFunc->arg_begin();
203   for (llvm::Function *Kernel : EmittedKernels) {
204     llvm::Constant *KernelName = makeConstantString(Kernel->getName());
205     llvm::Constant *NullPtr = llvm::ConstantPointerNull::get(VoidPtrTy);
206     llvm::Value *Args[] = {
207         &GpuBinaryHandlePtr, Builder.CreateBitCast(Kernel, VoidPtrTy),
208         KernelName, KernelName, llvm::ConstantInt::get(IntTy, -1), NullPtr,
209         NullPtr, NullPtr, NullPtr,
210         llvm::ConstantPointerNull::get(IntTy->getPointerTo())};
211     Builder.CreateCall(RegisterFunc, Args);
212   }
213 
214   // void __cudaRegisterVar(void **, char *, char *, const char *,
215   //                        int, int, int, int)
216   llvm::Type *RegisterVarParams[] = {VoidPtrPtrTy, CharPtrTy, CharPtrTy,
217                                      CharPtrTy,    IntTy,     IntTy,
218                                      IntTy,        IntTy};
219   llvm::Constant *RegisterVar = CGM.CreateRuntimeFunction(
220       llvm::FunctionType::get(IntTy, RegisterVarParams, false),
221       "__cudaRegisterVar");
222   for (auto &Pair : DeviceVars) {
223     llvm::GlobalVariable *Var = Pair.first;
224     unsigned Flags = Pair.second;
225     llvm::Constant *VarName = makeConstantString(Var->getName());
226     uint64_t VarSize =
227         CGM.getDataLayout().getTypeAllocSize(Var->getValueType());
228     llvm::Value *Args[] = {
229         &GpuBinaryHandlePtr,
230         Builder.CreateBitCast(Var, VoidPtrTy),
231         VarName,
232         VarName,
233         llvm::ConstantInt::get(IntTy, (Flags & ExternDeviceVar) ? 1 : 0),
234         llvm::ConstantInt::get(IntTy, VarSize),
235         llvm::ConstantInt::get(IntTy, (Flags & ConstantDeviceVar) ? 1 : 0),
236         llvm::ConstantInt::get(IntTy, 0)};
237     Builder.CreateCall(RegisterVar, Args);
238   }
239 
240   Builder.CreateRetVoid();
241   return RegisterKernelsFunc;
242 }
243 
244 /// Creates a global constructor function for the module:
245 /// \code
246 /// void __cuda_module_ctor(void*) {
247 ///     Handle0 = __cudaRegisterFatBinary(GpuBinaryBlob0);
248 ///     __cuda_register_globals(Handle0);
249 ///     ...
250 ///     HandleN = __cudaRegisterFatBinary(GpuBinaryBlobN);
251 ///     __cuda_register_globals(HandleN);
252 /// }
253 /// \endcode
makeModuleCtorFunction()254 llvm::Function *CGNVCUDARuntime::makeModuleCtorFunction() {
255   // No need to generate ctors/dtors if there are no GPU binaries.
256   if (CGM.getCodeGenOpts().CudaGpuBinaryFileNames.empty())
257     return nullptr;
258 
259   // void __cuda_register_globals(void* handle);
260   llvm::Function *RegisterGlobalsFunc = makeRegisterGlobalsFn();
261   // void ** __cudaRegisterFatBinary(void *);
262   llvm::Constant *RegisterFatbinFunc = CGM.CreateRuntimeFunction(
263       llvm::FunctionType::get(VoidPtrPtrTy, VoidPtrTy, false),
264       "__cudaRegisterFatBinary");
265   // struct { int magic, int version, void * gpu_binary, void * dont_care };
266   llvm::StructType *FatbinWrapperTy =
267       llvm::StructType::get(IntTy, IntTy, VoidPtrTy, VoidPtrTy, nullptr);
268 
269   llvm::Function *ModuleCtorFunc = llvm::Function::Create(
270       llvm::FunctionType::get(VoidTy, VoidPtrTy, false),
271       llvm::GlobalValue::InternalLinkage, "__cuda_module_ctor", &TheModule);
272   llvm::BasicBlock *CtorEntryBB =
273       llvm::BasicBlock::Create(Context, "entry", ModuleCtorFunc);
274   CGBuilderTy CtorBuilder(CGM, Context);
275 
276   CtorBuilder.SetInsertPoint(CtorEntryBB);
277 
278   // For each GPU binary, register it with the CUDA runtime and store returned
279   // handle in a global variable and save the handle in GpuBinaryHandles vector
280   // to be cleaned up in destructor on exit. Then associate all known kernels
281   // with the GPU binary handle so CUDA runtime can figure out what to call on
282   // the GPU side.
283   for (const std::string &GpuBinaryFileName :
284        CGM.getCodeGenOpts().CudaGpuBinaryFileNames) {
285     llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> GpuBinaryOrErr =
286         llvm::MemoryBuffer::getFileOrSTDIN(GpuBinaryFileName);
287     if (std::error_code EC = GpuBinaryOrErr.getError()) {
288       CGM.getDiags().Report(diag::err_cannot_open_file) << GpuBinaryFileName
289                                                         << EC.message();
290       continue;
291     }
292 
293     // Create initialized wrapper structure that points to the loaded GPU binary
294     llvm::Constant *Values[] = {
295         llvm::ConstantInt::get(IntTy, 0x466243b1), // Fatbin wrapper magic.
296         llvm::ConstantInt::get(IntTy, 1),          // Fatbin version.
297         makeConstantString(GpuBinaryOrErr.get()->getBuffer(), "", 16), // Data.
298         llvm::ConstantPointerNull::get(VoidPtrTy)}; // Unused in fatbin v1.
299     llvm::GlobalVariable *FatbinWrapper = new llvm::GlobalVariable(
300         TheModule, FatbinWrapperTy, true, llvm::GlobalValue::InternalLinkage,
301         llvm::ConstantStruct::get(FatbinWrapperTy, Values),
302         "__cuda_fatbin_wrapper");
303     // NVIDIA's cuobjdump looks for fatbins in this section.
304     FatbinWrapper->setSection(".nvFatBinSegment");
305 
306     // GpuBinaryHandle = __cudaRegisterFatBinary(&FatbinWrapper);
307     llvm::CallInst *RegisterFatbinCall = CtorBuilder.CreateCall(
308         RegisterFatbinFunc,
309         CtorBuilder.CreateBitCast(FatbinWrapper, VoidPtrTy));
310     llvm::GlobalVariable *GpuBinaryHandle = new llvm::GlobalVariable(
311         TheModule, VoidPtrPtrTy, false, llvm::GlobalValue::InternalLinkage,
312         llvm::ConstantPointerNull::get(VoidPtrPtrTy), "__cuda_gpubin_handle");
313     CtorBuilder.CreateAlignedStore(RegisterFatbinCall, GpuBinaryHandle,
314                                    CGM.getPointerAlign());
315 
316     // Call __cuda_register_globals(GpuBinaryHandle);
317     if (RegisterGlobalsFunc)
318       CtorBuilder.CreateCall(RegisterGlobalsFunc, RegisterFatbinCall);
319 
320     // Save GpuBinaryHandle so we can unregister it in destructor.
321     GpuBinaryHandles.push_back(GpuBinaryHandle);
322   }
323 
324   CtorBuilder.CreateRetVoid();
325   return ModuleCtorFunc;
326 }
327 
328 /// Creates a global destructor function that unregisters all GPU code blobs
329 /// registered by constructor.
330 /// \code
331 /// void __cuda_module_dtor(void*) {
332 ///     __cudaUnregisterFatBinary(Handle0);
333 ///     ...
334 ///     __cudaUnregisterFatBinary(HandleN);
335 /// }
336 /// \endcode
makeModuleDtorFunction()337 llvm::Function *CGNVCUDARuntime::makeModuleDtorFunction() {
338   // No need for destructor if we don't have handles to unregister.
339   if (GpuBinaryHandles.empty())
340     return nullptr;
341 
342   // void __cudaUnregisterFatBinary(void ** handle);
343   llvm::Constant *UnregisterFatbinFunc = CGM.CreateRuntimeFunction(
344       llvm::FunctionType::get(VoidTy, VoidPtrPtrTy, false),
345       "__cudaUnregisterFatBinary");
346 
347   llvm::Function *ModuleDtorFunc = llvm::Function::Create(
348       llvm::FunctionType::get(VoidTy, VoidPtrTy, false),
349       llvm::GlobalValue::InternalLinkage, "__cuda_module_dtor", &TheModule);
350   llvm::BasicBlock *DtorEntryBB =
351       llvm::BasicBlock::Create(Context, "entry", ModuleDtorFunc);
352   CGBuilderTy DtorBuilder(CGM, Context);
353   DtorBuilder.SetInsertPoint(DtorEntryBB);
354 
355   for (llvm::GlobalVariable *GpuBinaryHandle : GpuBinaryHandles) {
356     auto HandleValue =
357       DtorBuilder.CreateAlignedLoad(GpuBinaryHandle, CGM.getPointerAlign());
358     DtorBuilder.CreateCall(UnregisterFatbinFunc, HandleValue);
359   }
360 
361   DtorBuilder.CreateRetVoid();
362   return ModuleDtorFunc;
363 }
364 
CreateNVCUDARuntime(CodeGenModule & CGM)365 CGCUDARuntime *CodeGen::CreateNVCUDARuntime(CodeGenModule &CGM) {
366   return new CGNVCUDARuntime(CGM);
367 }
368