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/Module.h"
26 #include "llvm/IR/Type.h"
27 #include "llvm/Pass.h"
28 #include "llvm/Support/CommandLine.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/raw_os_ostream.h"
31 #include "llvm/Transforms/Scalar.h"
32 #include <map>
33 #include <sstream>
34 #include <string>
35 #include <vector>
36 
37 #define NVVM_REFLECT_FUNCTION "__nvvm_reflect"
38 
39 using namespace llvm;
40 
41 #define DEBUG_TYPE "nvptx-reflect"
42 
43 namespace llvm { void initializeNVVMReflectPass(PassRegistry &); }
44 
45 namespace {
46 class NVVMReflect : public ModulePass {
47 private:
48   StringMap<int> VarMap;
49   typedef DenseMap<std::string, int>::iterator VarMapIter;
50   Function *ReflectFunction;
51 
52 public:
53   static char ID;
54   NVVMReflect() : ModulePass(ID), ReflectFunction(nullptr) {
55     initializeNVVMReflectPass(*PassRegistry::getPassRegistry());
56     VarMap.clear();
57   }
58 
59   NVVMReflect(const StringMap<int> &Mapping)
60   : ModulePass(ID), ReflectFunction(nullptr) {
61     initializeNVVMReflectPass(*PassRegistry::getPassRegistry());
62     for (StringMap<int>::const_iterator I = Mapping.begin(), E = Mapping.end();
63          I != E; ++I) {
64       VarMap[(*I).getKey()] = (*I).getValue();
65     }
66   }
67 
68   void getAnalysisUsage(AnalysisUsage &AU) const override {
69     AU.setPreservesAll();
70   }
71   bool runOnModule(Module &) override;
72 
73   void setVarMap();
74 };
75 }
76 
77 ModulePass *llvm::createNVVMReflectPass() {
78   return new NVVMReflect();
79 }
80 
81 ModulePass *llvm::createNVVMReflectPass(const StringMap<int>& Mapping) {
82   return new NVVMReflect(Mapping);
83 }
84 
85 static cl::opt<bool>
86 NVVMReflectEnabled("nvvm-reflect-enable", cl::init(true), cl::Hidden,
87                    cl::desc("NVVM reflection, enabled by default"));
88 
89 char NVVMReflect::ID = 0;
90 INITIALIZE_PASS(NVVMReflect, "nvvm-reflect",
91                 "Replace occurrences of __nvvm_reflect() calls with 0/1", false,
92                 false)
93 
94 static cl::list<std::string>
95 ReflectList("nvvm-reflect-list", cl::value_desc("name=<int>"), cl::Hidden,
96             cl::desc("A list of string=num assignments"),
97             cl::ValueRequired);
98 
99 /// The command line can look as follows :
100 /// -nvvm-reflect-list a=1,b=2 -nvvm-reflect-list c=3,d=0 -R e=2
101 /// The strings "a=1,b=2", "c=3,d=0", "e=2" are available in the
102 /// ReflectList vector. First, each of ReflectList[i] is 'split'
103 /// using "," as the delimiter. Then each of this part is split
104 /// using "=" as the delimiter.
105 void NVVMReflect::setVarMap() {
106   for (unsigned i = 0, e = ReflectList.size(); i != e; ++i) {
107     DEBUG(dbgs() << "Option : "  << ReflectList[i] << "\n");
108     SmallVector<StringRef, 4> NameValList;
109     StringRef(ReflectList[i]).split(NameValList, ",");
110     for (unsigned j = 0, ej = NameValList.size(); j != ej; ++j) {
111       SmallVector<StringRef, 2> NameValPair;
112       NameValList[j].split(NameValPair, "=");
113       assert(NameValPair.size() == 2 && "name=val expected");
114       std::stringstream ValStream(NameValPair[1]);
115       int Val;
116       ValStream >> Val;
117       assert((!(ValStream.fail())) && "integer value expected");
118       VarMap[NameValPair[0]] = Val;
119     }
120   }
121 }
122 
123 bool NVVMReflect::runOnModule(Module &M) {
124   if (!NVVMReflectEnabled)
125     return false;
126 
127   setVarMap();
128 
129   ReflectFunction = M.getFunction(NVVM_REFLECT_FUNCTION);
130 
131   // If reflect function is not used, then there will be
132   // no entry in the module.
133   if (!ReflectFunction)
134     return false;
135 
136   // Validate _reflect function
137   assert(ReflectFunction->isDeclaration() &&
138          "_reflect function should not have a body");
139   assert(ReflectFunction->getReturnType()->isIntegerTy() &&
140          "_reflect's return type should be integer");
141 
142   std::vector<Instruction *> ToRemove;
143 
144   // Go through the uses of ReflectFunction in this Function.
145   // Each of them should a CallInst with a ConstantArray argument.
146   // First validate that. If the c-string corresponding to the
147   // ConstantArray can be found successfully, see if it can be
148   // found in VarMap. If so, replace the uses of CallInst with the
149   // value found in VarMap. If not, replace the use  with value 0.
150   for (User *U : ReflectFunction->users()) {
151     assert(isa<CallInst>(U) && "Only a call instruction can use _reflect");
152     CallInst *Reflect = cast<CallInst>(U);
153 
154     assert((Reflect->getNumOperands() == 2) &&
155            "Only one operand expect for _reflect function");
156     // In cuda, we will have an extra constant-to-generic conversion of
157     // the string.
158     const Value *conv = Reflect->getArgOperand(0);
159     assert(isa<CallInst>(conv) && "Expected a const-to-gen conversion");
160     const CallInst *ConvCall = cast<CallInst>(conv);
161     const Value *str = ConvCall->getArgOperand(0);
162     assert(isa<ConstantExpr>(str) &&
163            "Format of _reflect function not recognized");
164     const ConstantExpr *GEP = cast<ConstantExpr>(str);
165 
166     const Value *Sym = GEP->getOperand(0);
167     assert(isa<Constant>(Sym) && "Format of _reflect function not recognized");
168 
169     const Constant *SymStr = cast<Constant>(Sym);
170 
171     assert(isa<ConstantDataSequential>(SymStr->getOperand(0)) &&
172            "Format of _reflect function not recognized");
173 
174     assert(cast<ConstantDataSequential>(SymStr->getOperand(0))->isCString() &&
175            "Format of _reflect function not recognized");
176 
177     std::string ReflectArg =
178         cast<ConstantDataSequential>(SymStr->getOperand(0))->getAsString();
179 
180     ReflectArg = ReflectArg.substr(0, ReflectArg.size() - 1);
181     DEBUG(dbgs() << "Arg of _reflect : " << ReflectArg << "\n");
182 
183     int ReflectVal = 0; // The default value is 0
184     if (VarMap.find(ReflectArg) != VarMap.end()) {
185       ReflectVal = VarMap[ReflectArg];
186     }
187     Reflect->replaceAllUsesWith(
188         ConstantInt::get(Reflect->getType(), ReflectVal));
189     ToRemove.push_back(Reflect);
190   }
191   if (ToRemove.size() == 0)
192     return false;
193 
194   for (unsigned i = 0, e = ToRemove.size(); i != e; ++i)
195     ToRemove[i]->eraseFromParent();
196   return true;
197 }
198