|
| 1 | +//===------ MutatePrintfAddrspace.cpp - SYCL printf AS mutation Pass ------===// |
| 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 | +// A transformation pass which detects non-constant address space |
| 10 | +// literals usage for the first argument of SYCL experimental printf |
| 11 | +// function, and moves the string literal to constant address |
| 12 | +// space. This a temporary solution for printf's support of generic |
| 13 | +// address space literals; the pass should be dropped once SYCL device |
| 14 | +// backends learn to handle the generic address-spaced argument properly. |
| 15 | +//===----------------------------------------------------------------------===// |
| 16 | + |
| 17 | +#include "llvm/SYCLLowerIR/MutatePrintfAddrspace.h" |
| 18 | + |
| 19 | +#include "llvm/Analysis/ValueTracking.h" |
| 20 | +#include "llvm/IR/IRBuilder.h" |
| 21 | +#include "llvm/IR/Instructions.h" |
| 22 | +#include "llvm/InitializePasses.h" |
| 23 | + |
| 24 | +using namespace llvm; |
| 25 | + |
| 26 | +namespace { |
| 27 | +// Wrapper for the pass to make it working with the old pass manager |
| 28 | +class SYCLMutatePrintfAddrspaceLegacyPass : public ModulePass { |
| 29 | +public: |
| 30 | + static char ID; |
| 31 | + SYCLMutatePrintfAddrspaceLegacyPass() : ModulePass(ID) { |
| 32 | + initializeSYCLMutatePrintfAddrspaceLegacyPassPass( |
| 33 | + *PassRegistry::getPassRegistry()); |
| 34 | + } |
| 35 | + |
| 36 | + // run the SYCLMutatePrintfAddrspace pass on the specified module |
| 37 | + bool runOnModule(Module &M) override { |
| 38 | + ModuleAnalysisManager MAM; |
| 39 | + auto PA = Impl.run(M, MAM); |
| 40 | + return !PA.areAllPreserved(); |
| 41 | + } |
| 42 | + |
| 43 | +private: |
| 44 | + SYCLMutatePrintfAddrspacePass Impl; |
| 45 | +}; |
| 46 | + |
| 47 | +static constexpr unsigned ConstantAddrspaceID = 2; |
| 48 | +// If the variadic version gets picked during FE compilation, we'll only have |
| 49 | +// 1 function to replace. However, unique declarations are emitted for each |
| 50 | +// of the non-variadic (variadic template) calls. |
| 51 | +using FunctionVecTy = SmallVector<Function *, 8>; |
| 52 | + |
| 53 | +Function *getCASPrintfFunction(Module &M, PointerType *CASLiteralType); |
| 54 | +size_t setFuncCallsOntoCASPrintf(Function *F, Function *CASPrintfFunc, |
| 55 | + FunctionVecTy &FunctionsToDrop); |
| 56 | +} // namespace |
| 57 | + |
| 58 | +char SYCLMutatePrintfAddrspaceLegacyPass::ID = 0; |
| 59 | +INITIALIZE_PASS(SYCLMutatePrintfAddrspaceLegacyPass, |
| 60 | + "SYCLMutatePrintfAddrspace", |
| 61 | + "Move SYCL printf literal arguments to constant address space", |
| 62 | + false, false) |
| 63 | + |
| 64 | +// Public interface to the SYCLMutatePrintfAddrspacePass. |
| 65 | +ModulePass *llvm::createSYCLMutatePrintfAddrspaceLegacyPass() { |
| 66 | + return new SYCLMutatePrintfAddrspaceLegacyPass(); |
| 67 | +} |
| 68 | + |
| 69 | +PreservedAnalyses |
| 70 | +SYCLMutatePrintfAddrspacePass::run(Module &M, ModuleAnalysisManager &MAM) { |
| 71 | + Type *Int8Type = Type::getInt8Ty(M.getContext()); |
| 72 | + auto *CASLiteralType = PointerType::get(Int8Type, ConstantAddrspaceID); |
| 73 | + Function *CASPrintfFunc = getCASPrintfFunction(M, CASLiteralType); |
| 74 | + |
| 75 | + FunctionVecTy FunctionsToDrop; |
| 76 | + bool ModuleChanged = false; |
| 77 | + for (Function &F : M) { |
| 78 | + if (!F.isDeclaration()) |
| 79 | + continue; |
| 80 | + if (!F.getName().startswith("_Z18__spirv_ocl_printf")) |
| 81 | + continue; |
| 82 | + if (F.getArg(0)->getType() == CASLiteralType) |
| 83 | + // No need to replace the literal type and its printf users |
| 84 | + continue; |
| 85 | + ModuleChanged |= |
| 86 | + setFuncCallsOntoCASPrintf(&F, CASPrintfFunc, FunctionsToDrop); |
| 87 | + } |
| 88 | + for (Function *F : FunctionsToDrop) |
| 89 | + F->eraseFromParent(); |
| 90 | + |
| 91 | + return ModuleChanged ? PreservedAnalyses::all() : PreservedAnalyses::none(); |
| 92 | +} |
| 93 | + |
| 94 | +/// Helper implementations |
| 95 | +namespace { |
| 96 | + |
| 97 | +/// Get the constant addrspace version of the __spirv_ocl_printf declaration, |
| 98 | +/// or generate it if the IR module doesn't have it yet. Also make it |
| 99 | +/// variadic so that it could replace all non-variadic generic AS versions. |
| 100 | +Function *getCASPrintfFunction(Module &M, PointerType *CASLiteralType) { |
| 101 | + Type *Int32Type = Type::getInt32Ty(M.getContext()); |
| 102 | + auto *CASPrintfFuncTy = FunctionType::get(Int32Type, CASLiteralType, |
| 103 | + /*isVarArg=*/true); |
| 104 | + // extern int __spirv_ocl_printf( |
| 105 | + // const __attribute__((opencl_constant)) char *Format, ...) |
| 106 | + FunctionCallee CASPrintfFuncCallee = |
| 107 | + M.getOrInsertFunction("_Z18__spirv_ocl_printfPU3AS2Kcz", CASPrintfFuncTy); |
| 108 | + auto *CASPrintfFunc = cast<Function>(CASPrintfFuncCallee.getCallee()); |
| 109 | + CASPrintfFunc->setCallingConv(CallingConv::SPIR_FUNC); |
| 110 | + CASPrintfFunc->setDSOLocal(true); |
| 111 | + return CASPrintfFunc; |
| 112 | +} |
| 113 | + |
| 114 | +/// Generate the constant addrspace version of the generic addrspace-residing |
| 115 | +/// global string. If one exists already, get it from the module. |
| 116 | +Constant *getCASLiteral(GlobalVariable *GenericASLiteral) { |
| 117 | + Module *M = GenericASLiteral->getParent(); |
| 118 | + // Appending the stable suffix ensures that only one CAS copy is made for each |
| 119 | + // string. In case of the matching name, llvm::Module APIs will ensure that |
| 120 | + // the existing global is returned. |
| 121 | + std::string CASLiteralName = GenericASLiteral->getName().str() + "._AS2"; |
| 122 | + if (GlobalVariable *ExistingGlobal = |
| 123 | + M->getGlobalVariable(CASLiteralName, /*AllowInternal=*/true)) |
| 124 | + return ExistingGlobal; |
| 125 | + |
| 126 | + StringRef LiteralValue; |
| 127 | + getConstantStringInfo(GenericASLiteral, LiteralValue); |
| 128 | + IRBuilder<> Builder(M->getContext()); |
| 129 | + GlobalVariable *Res = Builder.CreateGlobalString(LiteralValue, CASLiteralName, |
| 130 | + ConstantAddrspaceID, M); |
| 131 | + Res->setLinkage(GlobalValue::LinkageTypes::InternalLinkage); |
| 132 | + Res->setUnnamedAddr(GlobalValue::UnnamedAddr::None); |
| 133 | + return Res; |
| 134 | +} |
| 135 | + |
| 136 | +/// Encapsulates the update of CallInst's literal argument. |
| 137 | +void setCallArgOntoCASPrintf(CallInst *CI, Constant *CASArg, |
| 138 | + Function *CASPrintfFunc) { |
| 139 | + CI->setCalledFunction(CASPrintfFunc); |
| 140 | + auto *Const = CASArg; |
| 141 | + // In case there's a misalignment between the updated function type and |
| 142 | + // the constant literal type, create a constant pointer cast so as to |
| 143 | + // duck module verifier complaints. |
| 144 | + Type *ParamType = CASPrintfFunc->getFunctionType()->getParamType(0); |
| 145 | + if (Const->getType() != ParamType) |
| 146 | + Const = ConstantExpr::getPointerCast(Const, ParamType); |
| 147 | + CI->setArgOperand(0, Const); |
| 148 | +} |
| 149 | + |
| 150 | +/// The function's effect is similar to V->stripPointerCastsAndAliases(), but |
| 151 | +/// also strips load/store aliases. |
| 152 | +/// NB: This function can only operate on simple CFG, where load/store pairs |
| 153 | +/// leading to the global variable are merely a consequence of low optimization |
| 154 | +/// level. Re-using it for complex CFG with arbitrary memory paths is definitely |
| 155 | +/// not recommended. |
| 156 | +Value *stripToMemorySource(Value *V) { |
| 157 | + Value *MemoryAccess = V; |
| 158 | + if (auto *LI = dyn_cast<LoadInst>(MemoryAccess)) { |
| 159 | + Value *LoadSource = LI->getPointerOperand(); |
| 160 | + auto *Store = cast<StoreInst>(*llvm::find_if( |
| 161 | + LoadSource->users(), [](User *U) { return isa<StoreInst>(U); })); |
| 162 | + MemoryAccess = Store->getValueOperand(); |
| 163 | + } |
| 164 | + return MemoryAccess->stripPointerCastsAndAliases(); |
| 165 | +} |
| 166 | + |
| 167 | +void emitError(Function *PrintfInstance, CallInst *PrintfCall, |
| 168 | + StringRef RecommendationToUser = "") { |
| 169 | + std::string ErrorMsg = |
| 170 | + std::string("experimental::printf requires format string to reside " |
| 171 | + "in constant " |
| 172 | + "address space. The compiler wasn't able to " |
| 173 | + "automatically convert " |
| 174 | + "your format string into constant address space when " |
| 175 | + "processing builtin ") + |
| 176 | + PrintfInstance->getName().str() + " called in function " + |
| 177 | + PrintfCall->getFunction()->getName().str() + ".\n" + |
| 178 | + RecommendationToUser.str(); |
| 179 | + PrintfInstance->getContext().emitError(PrintfCall, ErrorMsg); |
| 180 | +} |
| 181 | + |
| 182 | +/// This routine goes over CallInst users of F, resetting the called function |
| 183 | +/// to CASPrintfFunc and generating/retracting constant addrspace format |
| 184 | +/// strings to use as operands of the mutated calls. |
| 185 | +size_t setFuncCallsOntoCASPrintf(Function *F, Function *CASPrintfFunc, |
| 186 | + FunctionVecTy &FunctionsToDrop) { |
| 187 | + size_t MutatedCallsCount = 0; |
| 188 | + SmallVector<std::pair<CallInst *, Constant *>, 16> CallsToMutate; |
| 189 | + for (User *U : F->users()) { |
| 190 | + if (!isa<CallInst>(U)) |
| 191 | + continue; |
| 192 | + auto *CI = cast<CallInst>(U); |
| 193 | + |
| 194 | + // This key algorithm reaches the global string used as an argument to a |
| 195 | + // __spirv_ocl_printf call. It then generates a constant AS copy of that |
| 196 | + // global (or gets an existing one). For the return value, the call |
| 197 | + // instruction is paired with its future constant addrspace string |
| 198 | + // argument. |
| 199 | + Value *Stripped = stripToMemorySource(CI->getArgOperand(0)); |
| 200 | + if (auto *Literal = dyn_cast<GlobalVariable>(Stripped)) |
| 201 | + CallsToMutate.emplace_back(CI, getCASLiteral(Literal)); |
| 202 | + else if ( auto *Arg = dyn_cast<Argument>(Stripped)) { |
| 203 | + // The global literal is passed to __spirv_ocl_printf via a wrapper |
| 204 | + // function argument. We'll update the wrapper calls to use the builtin |
| 205 | + // function directly instead. |
| 206 | + Function *WrapperFunc = Arg->getParent(); |
| 207 | + std::string BadWrapperErrorMsg = |
| 208 | + "Consider simplifying the code by " |
| 209 | + "passing format strings directly into experimental::printf calls, " |
| 210 | + "avoiding indirection via wrapper function arguments."; |
| 211 | + if (!WrapperFunc->getName().contains("6oneapi12experimental6printf")) { |
| 212 | + emitError(WrapperFunc, CI, BadWrapperErrorMsg); |
| 213 | + return 0; |
| 214 | + } |
| 215 | + for (User *WrapperU : WrapperFunc->users()) { |
| 216 | + auto *WrapperCI = cast<CallInst>(WrapperU); |
| 217 | + Value *StrippedArg = stripToMemorySource(WrapperCI->getArgOperand(0)); |
| 218 | + auto *Literal = dyn_cast<GlobalVariable>(StrippedArg); |
| 219 | + // We only expect 1 level of wrappers |
| 220 | + if (!Literal) { |
| 221 | + emitError(WrapperFunc, WrapperCI, BadWrapperErrorMsg); |
| 222 | + return 0; |
| 223 | + } |
| 224 | + CallsToMutate.emplace_back(WrapperCI, getCASLiteral(Literal)); |
| 225 | + } |
| 226 | + // We're certain that the wrapper won't have any uses, since we've just |
| 227 | + // marked all its calls for replacement with __spirv_ocl_printf. |
| 228 | + FunctionsToDrop.emplace_back(WrapperFunc); |
| 229 | + // Similar certainty for the generic AS version of __spirv_ocl_printf |
| 230 | + // itself - we've determined it only gets called inside the |
| 231 | + // soon-to-be-removed wrapper. |
| 232 | + assert(F->hasOneUse() && "Unexpected __spirv_ocl_printf call outside of " |
| 233 | + "SYCL wrapper function"); |
| 234 | + FunctionsToDrop.emplace_back(F); |
| 235 | + } else { |
| 236 | + emitError( |
| 237 | + F, CI, |
| 238 | + "Make sure each format string literal is " |
| 239 | + "known at compile time or use OpenCL constant address space literals " |
| 240 | + "for device-side printf calls"); |
| 241 | + return 0; |
| 242 | + } |
| 243 | + } |
| 244 | + for (auto &CallConstantPair : CallsToMutate) { |
| 245 | + setCallArgOntoCASPrintf(CallConstantPair.first, CallConstantPair.second, |
| 246 | + CASPrintfFunc); |
| 247 | + ++MutatedCallsCount; |
| 248 | + } |
| 249 | + if (F->hasNUses(0)) |
| 250 | + FunctionsToDrop.emplace_back(F); |
| 251 | + return MutatedCallsCount; |
| 252 | +} |
| 253 | +} // namespace |
0 commit comments