1 //===- NVVMReflect.cpp - NVVM Emulate conditional compilation -------------===// 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 pass replaces occurrences of __nvvm_reflect("foo") and llvm.nvvm.reflect 11 // with an integer. 12 // 13 // We choose the value we use by looking, in this order, at: 14 // 15 // * the -nvvm-reflect-list flag, which has the format "foo=1,bar=42", 16 // * the StringMap passed to the pass's constructor, and 17 // * metadata in the module itself. 18 // 19 // If we see an unknown string, we replace its call with 0. 20 // 21 //===----------------------------------------------------------------------===// 22 23 #include "NVPTX.h" 24 #include "llvm/ADT/SmallVector.h" 25 #include "llvm/ADT/StringMap.h" 26 #include "llvm/IR/Constants.h" 27 #include "llvm/IR/DerivedTypes.h" 28 #include "llvm/IR/Function.h" 29 #include "llvm/IR/InstIterator.h" 30 #include "llvm/IR/Instructions.h" 31 #include "llvm/IR/Intrinsics.h" 32 #include "llvm/IR/Module.h" 33 #include "llvm/IR/Type.h" 34 #include "llvm/Pass.h" 35 #include "llvm/Support/CommandLine.h" 36 #include "llvm/Support/Debug.h" 37 #include "llvm/Support/raw_os_ostream.h" 38 #include "llvm/Support/raw_ostream.h" 39 #include "llvm/Transforms/Scalar.h" 40 #include <sstream> 41 #include <string> 42 #define NVVM_REFLECT_FUNCTION "__nvvm_reflect" 43 44 using namespace llvm; 45 46 #define DEBUG_TYPE "nvptx-reflect" 47 48 namespace llvm { void initializeNVVMReflectPass(PassRegistry &); } 49 50 namespace { 51 class NVVMReflect : public FunctionPass { 52 private: 53 StringMap<int> VarMap; 54 55 public: 56 static char ID; 57 NVVMReflect() : NVVMReflect(StringMap<int>()) {} 58 59 NVVMReflect(const StringMap<int> &Mapping) 60 : FunctionPass(ID), VarMap(Mapping) { 61 initializeNVVMReflectPass(*PassRegistry::getPassRegistry()); 62 setVarMap(); 63 } 64 65 bool runOnFunction(Function &) override; 66 67 private: 68 bool handleFunction(Function *ReflectFunction); 69 void setVarMap(); 70 }; 71 } 72 73 FunctionPass *llvm::createNVVMReflectPass() { return new NVVMReflect(); } 74 FunctionPass *llvm::createNVVMReflectPass(const StringMap<int> &Mapping) { 75 return new NVVMReflect(Mapping); 76 } 77 78 static cl::opt<bool> 79 NVVMReflectEnabled("nvvm-reflect-enable", cl::init(true), cl::Hidden, 80 cl::desc("NVVM reflection, enabled by default")); 81 82 char NVVMReflect::ID = 0; 83 INITIALIZE_PASS(NVVMReflect, "nvvm-reflect", 84 "Replace occurrences of __nvvm_reflect() calls with 0/1", false, 85 false) 86 87 static cl::list<std::string> 88 ReflectList("nvvm-reflect-list", cl::value_desc("name=<int>"), cl::Hidden, 89 cl::desc("A list of string=num assignments"), 90 cl::ValueRequired); 91 92 /// The command line can look as follows : 93 /// -nvvm-reflect-list a=1,b=2 -nvvm-reflect-list c=3,d=0 -R e=2 94 /// The strings "a=1,b=2", "c=3,d=0", "e=2" are available in the 95 /// ReflectList vector. First, each of ReflectList[i] is 'split' 96 /// using "," as the delimiter. Then each of this part is split 97 /// using "=" as the delimiter. 98 void NVVMReflect::setVarMap() { 99 for (unsigned i = 0, e = ReflectList.size(); i != e; ++i) { 100 DEBUG(dbgs() << "Option : " << ReflectList[i] << "\n"); 101 SmallVector<StringRef, 4> NameValList; 102 StringRef(ReflectList[i]).split(NameValList, ','); 103 for (unsigned j = 0, ej = NameValList.size(); j != ej; ++j) { 104 SmallVector<StringRef, 2> NameValPair; 105 NameValList[j].split(NameValPair, '='); 106 assert(NameValPair.size() == 2 && "name=val expected"); 107 std::stringstream ValStream(NameValPair[1]); 108 int Val; 109 ValStream >> Val; 110 assert((!(ValStream.fail())) && "integer value expected"); 111 VarMap[NameValPair[0]] = Val; 112 } 113 } 114 } 115 116 bool NVVMReflect::runOnFunction(Function &F) { 117 if (!NVVMReflectEnabled) 118 return false; 119 120 if (F.getName() == NVVM_REFLECT_FUNCTION) { 121 assert(F.isDeclaration() && "_reflect function should not have a body"); 122 assert(F.getReturnType()->isIntegerTy() && 123 "_reflect's return type should be integer"); 124 return false; 125 } 126 127 SmallVector<Instruction *, 4> ToRemove; 128 129 // Go through the calls in this function. Each call to __nvvm_reflect or 130 // llvm.nvvm.reflect should be a CallInst with a ConstantArray argument. 131 // First validate that. If the c-string corresponding to the ConstantArray can 132 // be found successfully, see if it can be found in VarMap. If so, replace the 133 // uses of CallInst with the value found in VarMap. If not, replace the use 134 // with value 0. 135 136 // The IR for __nvvm_reflect calls differs between CUDA versions. 137 // 138 // CUDA 6.5 and earlier uses this sequence: 139 // %ptr = tail call i8* @llvm.nvvm.ptr.constant.to.gen.p0i8.p4i8 140 // (i8 addrspace(4)* getelementptr inbounds 141 // ([8 x i8], [8 x i8] addrspace(4)* @str, i32 0, i32 0)) 142 // %reflect = tail call i32 @__nvvm_reflect(i8* %ptr) 143 // 144 // The value returned by Sym->getOperand(0) is a Constant with a 145 // ConstantDataSequential operand which can be converted to string and used 146 // for lookup. 147 // 148 // CUDA 7.0 does it slightly differently: 149 // %reflect = call i32 @__nvvm_reflect(i8* addrspacecast 150 // (i8 addrspace(1)* getelementptr inbounds 151 // ([8 x i8], [8 x i8] addrspace(1)* @str, i32 0, i32 0) to i8*)) 152 // 153 // In this case, we get a Constant with a GlobalVariable operand and we need 154 // to dig deeper to find its initializer with the string we'll use for lookup. 155 for (Instruction &I : instructions(F)) { 156 CallInst *Call = dyn_cast<CallInst>(&I); 157 if (!Call) 158 continue; 159 Function *Callee = Call->getCalledFunction(); 160 if (!Callee || (Callee->getName() != NVVM_REFLECT_FUNCTION && 161 Callee->getIntrinsicID() != Intrinsic::nvvm_reflect)) 162 continue; 163 164 // FIXME: Improve error handling here and elsewhere in this pass. 165 assert(Call->getNumOperands() == 2 && 166 "Wrong number of operands to __nvvm_reflect function"); 167 168 // In cuda 6.5 and earlier, we will have an extra constant-to-generic 169 // conversion of the string. 170 const Value *Str = Call->getArgOperand(0); 171 if (const CallInst *ConvCall = dyn_cast<CallInst>(Str)) { 172 // FIXME: Add assertions about ConvCall. 173 Str = ConvCall->getArgOperand(0); 174 } 175 assert(isa<ConstantExpr>(Str) && 176 "Format of __nvvm__reflect function not recognized"); 177 const ConstantExpr *GEP = cast<ConstantExpr>(Str); 178 179 const Value *Sym = GEP->getOperand(0); 180 assert(isa<Constant>(Sym) && 181 "Format of __nvvm_reflect function not recognized"); 182 183 const Value *Operand = cast<Constant>(Sym)->getOperand(0); 184 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Operand)) { 185 // For CUDA-7.0 style __nvvm_reflect calls, we need to find the operand's 186 // initializer. 187 assert(GV->hasInitializer() && 188 "Format of _reflect function not recognized"); 189 const Constant *Initializer = GV->getInitializer(); 190 Operand = Initializer; 191 } 192 193 assert(isa<ConstantDataSequential>(Operand) && 194 "Format of _reflect function not recognized"); 195 assert(cast<ConstantDataSequential>(Operand)->isCString() && 196 "Format of _reflect function not recognized"); 197 198 StringRef ReflectArg = cast<ConstantDataSequential>(Operand)->getAsString(); 199 ReflectArg = ReflectArg.substr(0, ReflectArg.size() - 1); 200 DEBUG(dbgs() << "Arg of _reflect : " << ReflectArg << "\n"); 201 202 int ReflectVal = 0; // The default value is 0 203 auto Iter = VarMap.find(ReflectArg); 204 if (Iter != VarMap.end()) 205 ReflectVal = Iter->second; 206 else if (ReflectArg == "__CUDA_FTZ") { 207 // Try to pull __CUDA_FTZ from the nvvm-reflect-ftz module flag. 208 if (auto *Flag = mdconst::extract_or_null<ConstantInt>( 209 F.getParent()->getModuleFlag("nvvm-reflect-ftz"))) 210 ReflectVal = Flag->getSExtValue(); 211 } 212 Call->replaceAllUsesWith(ConstantInt::get(Call->getType(), ReflectVal)); 213 ToRemove.push_back(Call); 214 } 215 216 for (Instruction *I : ToRemove) 217 I->eraseFromParent(); 218 219 return ToRemove.size() > 0; 220 } 221
