1 //===- NVVMReflect.cpp - NVVM Emulate conditional compilation -------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass replaces occurrences of __nvvm_reflect("foo") and llvm.nvvm.reflect
13 // We choose the value we use by looking, in this order, at:
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.
19 // If we see an unknown string, we replace its call with 0.
21 //===----------------------------------------------------------------------===//
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"
42 #define NVVM_REFLECT_FUNCTION "__nvvm_reflect"
46 #define DEBUG_TYPE "nvptx-reflect"
48 namespace llvm { void initializeNVVMReflectPass(PassRegistry &); }
51 class NVVMReflect : public FunctionPass {
53 StringMap<int> VarMap;
57 NVVMReflect() : NVVMReflect(StringMap<int>()) {}
59 NVVMReflect(const StringMap<int> &Mapping)
60 : FunctionPass(ID), VarMap(Mapping) {
61 initializeNVVMReflectPass(*PassRegistry::getPassRegistry());
65 bool runOnFunction(Function &) override;
72 FunctionPass *llvm::createNVVMReflectPass() { return new NVVMReflect(); }
73 FunctionPass *llvm::createNVVMReflectPass(const StringMap<int> &Mapping) {
74 return new NVVMReflect(Mapping);
78 NVVMReflectEnabled("nvvm-reflect-enable", cl::init(true), cl::Hidden,
79 cl::desc("NVVM reflection, enabled by default"));
81 char NVVMReflect::ID = 0;
82 INITIALIZE_PASS(NVVMReflect, "nvvm-reflect",
83 "Replace occurrences of __nvvm_reflect() calls with 0/1", false,
86 static cl::list<std::string>
87 ReflectList("nvvm-reflect-list", cl::value_desc("name=<int>"), cl::Hidden,
88 cl::desc("A list of string=num assignments"),
91 /// The command line can look as follows :
92 /// -nvvm-reflect-list a=1,b=2 -nvvm-reflect-list c=3,d=0 -R e=2
93 /// The strings "a=1,b=2", "c=3,d=0", "e=2" are available in the
94 /// ReflectList vector. First, each of ReflectList[i] is 'split'
95 /// using "," as the delimiter. Then each of this part is split
96 /// using "=" as the delimiter.
97 void NVVMReflect::setVarMap() {
98 for (unsigned i = 0, e = ReflectList.size(); i != e; ++i) {
99 DEBUG(dbgs() << "Option : " << ReflectList[i] << "\n");
100 SmallVector<StringRef, 4> NameValList;
101 StringRef(ReflectList[i]).split(NameValList, ',');
102 for (unsigned j = 0, ej = NameValList.size(); j != ej; ++j) {
103 SmallVector<StringRef, 2> NameValPair;
104 NameValList[j].split(NameValPair, '=');
105 assert(NameValPair.size() == 2 && "name=val expected");
106 std::stringstream ValStream(NameValPair[1]);
109 assert((!(ValStream.fail())) && "integer value expected");
110 VarMap[NameValPair[0]] = Val;
115 bool NVVMReflect::runOnFunction(Function &F) {
116 if (!NVVMReflectEnabled)
119 if (F.getName() == NVVM_REFLECT_FUNCTION) {
120 assert(F.isDeclaration() && "_reflect function should not have a body");
121 assert(F.getReturnType()->isIntegerTy() &&
122 "_reflect's return type should be integer");
126 SmallVector<Instruction *, 4> ToRemove;
128 // Go through the calls in this function. Each call to __nvvm_reflect or
129 // llvm.nvvm.reflect should be a CallInst with a ConstantArray argument.
130 // First validate that. If the c-string corresponding to the ConstantArray can
131 // be found successfully, see if it can be found in VarMap. If so, replace the
132 // uses of CallInst with the value found in VarMap. If not, replace the use
135 // The IR for __nvvm_reflect calls differs between CUDA versions.
137 // CUDA 6.5 and earlier uses this sequence:
138 // %ptr = tail call i8* @llvm.nvvm.ptr.constant.to.gen.p0i8.p4i8
139 // (i8 addrspace(4)* getelementptr inbounds
140 // ([8 x i8], [8 x i8] addrspace(4)* @str, i32 0, i32 0))
141 // %reflect = tail call i32 @__nvvm_reflect(i8* %ptr)
143 // The value returned by Sym->getOperand(0) is a Constant with a
144 // ConstantDataSequential operand which can be converted to string and used
147 // CUDA 7.0 does it slightly differently:
148 // %reflect = call i32 @__nvvm_reflect(i8* addrspacecast
149 // (i8 addrspace(1)* getelementptr inbounds
150 // ([8 x i8], [8 x i8] addrspace(1)* @str, i32 0, i32 0) to i8*))
152 // In this case, we get a Constant with a GlobalVariable operand and we need
153 // to dig deeper to find its initializer with the string we'll use for lookup.
154 for (Instruction &I : instructions(F)) {
155 CallInst *Call = dyn_cast<CallInst>(&I);
158 Function *Callee = Call->getCalledFunction();
159 if (!Callee || (Callee->getName() != NVVM_REFLECT_FUNCTION &&
160 Callee->getIntrinsicID() != Intrinsic::nvvm_reflect))
163 // FIXME: Improve error handling here and elsewhere in this pass.
164 assert(Call->getNumOperands() == 2 &&
165 "Wrong number of operands to __nvvm_reflect function");
167 // In cuda 6.5 and earlier, we will have an extra constant-to-generic
168 // conversion of the string.
169 const Value *Str = Call->getArgOperand(0);
170 if (const CallInst *ConvCall = dyn_cast<CallInst>(Str)) {
171 // FIXME: Add assertions about ConvCall.
172 Str = ConvCall->getArgOperand(0);
174 assert(isa<ConstantExpr>(Str) &&
175 "Format of __nvvm__reflect function not recognized");
176 const ConstantExpr *GEP = cast<ConstantExpr>(Str);
178 const Value *Sym = GEP->getOperand(0);
179 assert(isa<Constant>(Sym) &&
180 "Format of __nvvm_reflect function not recognized");
182 const Value *Operand = cast<Constant>(Sym)->getOperand(0);
183 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Operand)) {
184 // For CUDA-7.0 style __nvvm_reflect calls, we need to find the operand's
186 assert(GV->hasInitializer() &&
187 "Format of _reflect function not recognized");
188 const Constant *Initializer = GV->getInitializer();
189 Operand = Initializer;
192 assert(isa<ConstantDataSequential>(Operand) &&
193 "Format of _reflect function not recognized");
194 assert(cast<ConstantDataSequential>(Operand)->isCString() &&
195 "Format of _reflect function not recognized");
197 StringRef ReflectArg = cast<ConstantDataSequential>(Operand)->getAsString();
198 ReflectArg = ReflectArg.substr(0, ReflectArg.size() - 1);
199 DEBUG(dbgs() << "Arg of _reflect : " << ReflectArg << "\n");
201 int ReflectVal = 0; // The default value is 0
202 auto Iter = VarMap.find(ReflectArg);
203 if (Iter != VarMap.end())
204 ReflectVal = Iter->second;
205 else if (ReflectArg == "__CUDA_FTZ") {
206 // Try to pull __CUDA_FTZ from the nvvm-reflect-ftz module flag.
207 if (auto *Flag = mdconst::extract_or_null<ConstantInt>(
208 F.getParent()->getModuleFlag("nvvm-reflect-ftz")))
209 ReflectVal = Flag->getSExtValue();
211 Call->replaceAllUsesWith(ConstantInt::get(Call->getType(), ReflectVal));
212 ToRemove.push_back(Call);
215 for (Instruction *I : ToRemove)
216 I->eraseFromParent();
218 return ToRemove.size() > 0;