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("string") with an
11 // integer based on -nvvm-reflect-list string=<int> option given to this pass.
12 // If an undefined string value is seen in a call to __nvvm_reflect("string"),
13 // a default value of 0 will be used.
14 //
15 //===----------------------------------------------------------------------===//
16
17 #include "NVPTX.h"
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/SmallVector.h"
20 #include "llvm/ADT/StringMap.h"
21 #include "llvm/IR/Constants.h"
22 #include "llvm/IR/DerivedTypes.h"
23 #include "llvm/IR/Function.h"
24 #include "llvm/IR/Instructions.h"
25 #include "llvm/IR/Intrinsics.h"
26 #include "llvm/IR/Module.h"
27 #include "llvm/IR/Type.h"
28 #include "llvm/Pass.h"
29 #include "llvm/Support/CommandLine.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/raw_os_ostream.h"
32 #include "llvm/Support/raw_ostream.h"
33 #include "llvm/Transforms/Scalar.h"
34 #include <map>
35 #include <sstream>
36 #include <string>
37 #include <vector>
38
39 #define NVVM_REFLECT_FUNCTION "__nvvm_reflect"
40
41 using namespace llvm;
42
43 #define DEBUG_TYPE "nvptx-reflect"
44
45 namespace llvm { void initializeNVVMReflectPass(PassRegistry &); }
46
47 namespace {
48 class NVVMReflect : public ModulePass {
49 private:
50 StringMap<int> VarMap;
51 typedef DenseMap<std::string, int>::iterator VarMapIter;
52
53 public:
54 static char ID;
NVVMReflect()55 NVVMReflect() : ModulePass(ID) {
56 initializeNVVMReflectPass(*PassRegistry::getPassRegistry());
57 VarMap.clear();
58 }
59
NVVMReflect(const StringMap<int> & Mapping)60 NVVMReflect(const StringMap<int> &Mapping)
61 : ModulePass(ID) {
62 initializeNVVMReflectPass(*PassRegistry::getPassRegistry());
63 for (StringMap<int>::const_iterator I = Mapping.begin(), E = Mapping.end();
64 I != E; ++I) {
65 VarMap[(*I).getKey()] = (*I).getValue();
66 }
67 }
68
getAnalysisUsage(AnalysisUsage & AU) const69 void getAnalysisUsage(AnalysisUsage &AU) const override {
70 AU.setPreservesAll();
71 }
72 bool runOnModule(Module &) override;
73
74 private:
75 bool handleFunction(Function *ReflectFunction);
76 void setVarMap();
77 };
78 }
79
createNVVMReflectPass()80 ModulePass *llvm::createNVVMReflectPass() {
81 return new NVVMReflect();
82 }
83
createNVVMReflectPass(const StringMap<int> & Mapping)84 ModulePass *llvm::createNVVMReflectPass(const StringMap<int>& Mapping) {
85 return new NVVMReflect(Mapping);
86 }
87
88 static cl::opt<bool>
89 NVVMReflectEnabled("nvvm-reflect-enable", cl::init(true), cl::Hidden,
90 cl::desc("NVVM reflection, enabled by default"));
91
92 char NVVMReflect::ID = 0;
93 INITIALIZE_PASS(NVVMReflect, "nvvm-reflect",
94 "Replace occurrences of __nvvm_reflect() calls with 0/1", false,
95 false)
96
97 static cl::list<std::string>
98 ReflectList("nvvm-reflect-list", cl::value_desc("name=<int>"), cl::Hidden,
99 cl::desc("A list of string=num assignments"),
100 cl::ValueRequired);
101
102 /// The command line can look as follows :
103 /// -nvvm-reflect-list a=1,b=2 -nvvm-reflect-list c=3,d=0 -R e=2
104 /// The strings "a=1,b=2", "c=3,d=0", "e=2" are available in the
105 /// ReflectList vector. First, each of ReflectList[i] is 'split'
106 /// using "," as the delimiter. Then each of this part is split
107 /// using "=" as the delimiter.
setVarMap()108 void NVVMReflect::setVarMap() {
109 for (unsigned i = 0, e = ReflectList.size(); i != e; ++i) {
110 DEBUG(dbgs() << "Option : " << ReflectList[i] << "\n");
111 SmallVector<StringRef, 4> NameValList;
112 StringRef(ReflectList[i]).split(NameValList, ',');
113 for (unsigned j = 0, ej = NameValList.size(); j != ej; ++j) {
114 SmallVector<StringRef, 2> NameValPair;
115 NameValList[j].split(NameValPair, '=');
116 assert(NameValPair.size() == 2 && "name=val expected");
117 std::stringstream ValStream(NameValPair[1]);
118 int Val;
119 ValStream >> Val;
120 assert((!(ValStream.fail())) && "integer value expected");
121 VarMap[NameValPair[0]] = Val;
122 }
123 }
124 }
125
handleFunction(Function * ReflectFunction)126 bool NVVMReflect::handleFunction(Function *ReflectFunction) {
127 // Validate _reflect function
128 assert(ReflectFunction->isDeclaration() &&
129 "_reflect function should not have a body");
130 assert(ReflectFunction->getReturnType()->isIntegerTy() &&
131 "_reflect's return type should be integer");
132
133 std::vector<Instruction *> ToRemove;
134
135 // Go through the uses of ReflectFunction in this Function.
136 // Each of them should a CallInst with a ConstantArray argument.
137 // First validate that. If the c-string corresponding to the
138 // ConstantArray can be found successfully, see if it can be
139 // found in VarMap. If so, replace the uses of CallInst with the
140 // value found in VarMap. If not, replace the use with value 0.
141
142 // IR for __nvvm_reflect calls differs between CUDA versions:
143 // CUDA 6.5 and earlier uses this sequence:
144 // %ptr = tail call i8* @llvm.nvvm.ptr.constant.to.gen.p0i8.p4i8
145 // (i8 addrspace(4)* getelementptr inbounds
146 // ([8 x i8], [8 x i8] addrspace(4)* @str, i32 0, i32 0))
147 // %reflect = tail call i32 @__nvvm_reflect(i8* %ptr)
148 //
149 // Value returned by Sym->getOperand(0) is a Constant with a
150 // ConstantDataSequential operand which can be converted to string and used
151 // for lookup.
152 //
153 // CUDA 7.0 does it slightly differently:
154 // %reflect = call i32 @__nvvm_reflect(i8* addrspacecast
155 // (i8 addrspace(1)* getelementptr inbounds
156 // ([8 x i8], [8 x i8] addrspace(1)* @str, i32 0, i32 0) to i8*))
157 //
158 // In this case, we get a Constant with a GlobalVariable operand and we need
159 // to dig deeper to find its initializer with the string we'll use for lookup.
160
161 for (User *U : ReflectFunction->users()) {
162 assert(isa<CallInst>(U) && "Only a call instruction can use _reflect");
163 CallInst *Reflect = cast<CallInst>(U);
164
165 assert((Reflect->getNumOperands() == 2) &&
166 "Only one operand expect for _reflect function");
167 // In cuda, we will have an extra constant-to-generic conversion of
168 // the string.
169 const Value *Str = Reflect->getArgOperand(0);
170 if (isa<CallInst>(Str)) {
171 // CUDA path
172 const CallInst *ConvCall = cast<CallInst>(Str);
173 Str = ConvCall->getArgOperand(0);
174 }
175 assert(isa<ConstantExpr>(Str) &&
176 "Format of _reflect function not recognized");
177 const ConstantExpr *GEP = cast<ConstantExpr>(Str);
178
179 const Value *Sym = GEP->getOperand(0);
180 assert(isa<Constant>(Sym) && "Format of _reflect function not recognized");
181
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 operand's
185 // initializer.
186 assert(GV->hasInitializer() &&
187 "Format of _reflect function not recognized");
188 const Constant *Initializer = GV->getInitializer();
189 Operand = Initializer;
190 }
191
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");
196
197 std::string ReflectArg =
198 cast<ConstantDataSequential>(Operand)->getAsString();
199
200 ReflectArg = ReflectArg.substr(0, ReflectArg.size() - 1);
201 DEBUG(dbgs() << "Arg of _reflect : " << ReflectArg << "\n");
202
203 int ReflectVal = 0; // The default value is 0
204 if (VarMap.find(ReflectArg) != VarMap.end()) {
205 ReflectVal = VarMap[ReflectArg];
206 }
207 Reflect->replaceAllUsesWith(
208 ConstantInt::get(Reflect->getType(), ReflectVal));
209 ToRemove.push_back(Reflect);
210 }
211 if (ToRemove.size() == 0)
212 return false;
213
214 for (unsigned i = 0, e = ToRemove.size(); i != e; ++i)
215 ToRemove[i]->eraseFromParent();
216 return true;
217 }
218
runOnModule(Module & M)219 bool NVVMReflect::runOnModule(Module &M) {
220 if (!NVVMReflectEnabled)
221 return false;
222
223 setVarMap();
224
225
226 bool Res = false;
227 std::string Name;
228 Type *Tys[1];
229 Type *I8Ty = Type::getInt8Ty(M.getContext());
230 Function *ReflectFunction;
231
232 // Check for standard overloaded versions of llvm.nvvm.reflect
233
234 for (unsigned i = 0; i != 5; ++i) {
235 Tys[0] = PointerType::get(I8Ty, i);
236 Name = Intrinsic::getName(Intrinsic::nvvm_reflect, Tys);
237 ReflectFunction = M.getFunction(Name);
238 if(ReflectFunction != 0) {
239 Res |= handleFunction(ReflectFunction);
240 }
241 }
242
243 ReflectFunction = M.getFunction(NVVM_REFLECT_FUNCTION);
244 // If reflect function is not used, then there will be
245 // no entry in the module.
246 if (ReflectFunction != 0)
247 Res |= handleFunction(ReflectFunction);
248
249 return Res;
250 }
251