NVVMReflect.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
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
39using namespace llvm;
40
41namespace llvm { void initializeNVVMReflectPass(PassRegistry &); }
42
43namespace {
44class NVVMReflect : public ModulePass {
45private:
46  StringMap<int> VarMap;
47  typedef DenseMap<std::string, int>::iterator VarMapIter;
48  Function *ReflectFunction;
49
50public:
51  static char ID;
52  NVVMReflect() : ModulePass(ID), ReflectFunction(0) {
53    initializeNVVMReflectPass(*PassRegistry::getPassRegistry());
54    VarMap.clear();
55  }
56
57  NVVMReflect(const StringMap<int> &Mapping)
58  : ModulePass(ID), ReflectFunction(0) {
59    initializeNVVMReflectPass(*PassRegistry::getPassRegistry());
60    for (StringMap<int>::const_iterator I = Mapping.begin(), E = Mapping.end();
61         I != E; ++I) {
62      VarMap[(*I).getKey()] = (*I).getValue();
63    }
64  }
65
66  void getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesAll(); }
67  virtual bool runOnModule(Module &);
68
69  void setVarMap();
70};
71}
72
73ModulePass *llvm::createNVVMReflectPass() {
74  return new NVVMReflect();
75}
76
77ModulePass *llvm::createNVVMReflectPass(const StringMap<int>& Mapping) {
78  return new NVVMReflect(Mapping);
79}
80
81static cl::opt<bool>
82NVVMReflectEnabled("nvvm-reflect-enable", cl::init(true), cl::Hidden,
83                   cl::desc("NVVM reflection, enabled by default"));
84
85char NVVMReflect::ID = 0;
86INITIALIZE_PASS(NVVMReflect, "nvvm-reflect",
87                "Replace occurrences of __nvvm_reflect() calls with 0/1", false,
88                false)
89
90static cl::list<std::string>
91ReflectList("nvvm-reflect-list", cl::value_desc("name=<int>"), cl::Hidden,
92            cl::desc("A list of string=num assignments"),
93            cl::ValueRequired);
94
95/// The command line can look as follows :
96/// -nvvm-reflect-list a=1,b=2 -nvvm-reflect-list c=3,d=0 -R e=2
97/// The strings "a=1,b=2", "c=3,d=0", "e=2" are available in the
98/// ReflectList vector. First, each of ReflectList[i] is 'split'
99/// using "," as the delimiter. Then each of this part is split
100/// using "=" as the delimiter.
101void NVVMReflect::setVarMap() {
102  for (unsigned i = 0, e = ReflectList.size(); i != e; ++i) {
103    DEBUG(dbgs() << "Option : "  << ReflectList[i] << "\n");
104    SmallVector<StringRef, 4> NameValList;
105    StringRef(ReflectList[i]).split(NameValList, ",");
106    for (unsigned j = 0, ej = NameValList.size(); j != ej; ++j) {
107      SmallVector<StringRef, 2> NameValPair;
108      NameValList[j].split(NameValPair, "=");
109      assert(NameValPair.size() == 2 && "name=val expected");
110      std::stringstream ValStream(NameValPair[1]);
111      int Val;
112      ValStream >> Val;
113      assert((!(ValStream.fail())) && "integer value expected");
114      VarMap[NameValPair[0]] = Val;
115    }
116  }
117}
118
119bool NVVMReflect::runOnModule(Module &M) {
120  if (!NVVMReflectEnabled)
121    return false;
122
123  setVarMap();
124
125  ReflectFunction = M.getFunction(NVVM_REFLECT_FUNCTION);
126
127  // If reflect function is not used, then there will be
128  // no entry in the module.
129  if (ReflectFunction == 0)
130    return false;
131
132  // Validate _reflect function
133  assert(ReflectFunction->isDeclaration() &&
134         "_reflect function should not have a body");
135  assert(ReflectFunction->getReturnType()->isIntegerTy() &&
136         "_reflect's return type should be integer");
137
138  std::vector<Instruction *> ToRemove;
139
140  // Go through the uses of ReflectFunction in this Function.
141  // Each of them should a CallInst with a ConstantArray argument.
142  // First validate that. If the c-string corresponding to the
143  // ConstantArray can be found successfully, see if it can be
144  // found in VarMap. If so, replace the uses of CallInst with the
145  // value found in VarMap. If not, replace the use  with value 0.
146  for (User *U : ReflectFunction->users()) {
147    assert(isa<CallInst>(U) && "Only a call instruction can use _reflect");
148    CallInst *Reflect = cast<CallInst>(U);
149
150    assert((Reflect->getNumOperands() == 2) &&
151           "Only one operand expect for _reflect function");
152    // In cuda, we will have an extra constant-to-generic conversion of
153    // the string.
154    const Value *conv = Reflect->getArgOperand(0);
155    assert(isa<CallInst>(conv) && "Expected a const-to-gen conversion");
156    const CallInst *ConvCall = cast<CallInst>(conv);
157    const Value *str = ConvCall->getArgOperand(0);
158    assert(isa<ConstantExpr>(str) &&
159           "Format of _reflect function not recognized");
160    const ConstantExpr *GEP = cast<ConstantExpr>(str);
161
162    const Value *Sym = GEP->getOperand(0);
163    assert(isa<Constant>(Sym) && "Format of _reflect function not recognized");
164
165    const Constant *SymStr = cast<Constant>(Sym);
166
167    assert(isa<ConstantDataSequential>(SymStr->getOperand(0)) &&
168           "Format of _reflect function not recognized");
169
170    assert(cast<ConstantDataSequential>(SymStr->getOperand(0))->isCString() &&
171           "Format of _reflect function not recognized");
172
173    std::string ReflectArg =
174        cast<ConstantDataSequential>(SymStr->getOperand(0))->getAsString();
175
176    ReflectArg = ReflectArg.substr(0, ReflectArg.size() - 1);
177    DEBUG(dbgs() << "Arg of _reflect : " << ReflectArg << "\n");
178
179    int ReflectVal = 0; // The default value is 0
180    if (VarMap.find(ReflectArg) != VarMap.end()) {
181      ReflectVal = VarMap[ReflectArg];
182    }
183    Reflect->replaceAllUsesWith(
184        ConstantInt::get(Reflect->getType(), ReflectVal));
185    ToRemove.push_back(Reflect);
186  }
187  if (ToRemove.size() == 0)
188    return false;
189
190  for (unsigned i = 0, e = ToRemove.size(); i != e; ++i)
191    ToRemove[i]->eraseFromParent();
192  return true;
193}
194