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