1 //===- ValueMapper.cpp - Interface shared by lib/Transforms/Utils ---------===//
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 file defines the MapValue function, which is shared by various parts of
11 // the lib/Transforms/Utils library.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/Transforms/Utils/ValueMapper.h"
16 #include "llvm/Type.h"
17 #include "llvm/Constants.h"
18 #include "llvm/Function.h"
19 #include "llvm/Metadata.h"
20 #include "llvm/ADT/SmallVector.h"
21 using namespace llvm;
22 
23 Value *llvm::MapValue(const Value *V, ValueToValueMapTy &VM,
24                       bool ModuleLevelChanges) {
25   TrackingVH<Value> &VMSlot = VM[V];
26   if (VMSlot) return VMSlot;      // Does it exist in the map yet?
27 
28   // NOTE: VMSlot can be invalidated by any reference to VM, which can grow the
29   // DenseMap.  This includes any recursive calls to MapValue.
30 
31   // Global values do not need to be seeded into the VM if they
32   // are using the identity mapping.
33   if (isa<GlobalValue>(V) || isa<InlineAsm>(V) || isa<MDString>(V) ||
34       (isa<MDNode>(V) && !cast<MDNode>(V)->isFunctionLocal() &&
35        !ModuleLevelChanges))
36     return VMSlot = const_cast<Value*>(V);
37 
38   if (const MDNode *MD = dyn_cast<MDNode>(V)) {
39     // Start by assuming that we'll use the identity mapping.
40     VMSlot = const_cast<Value*>(V);
41 
42     // Check all operands to see if any need to be remapped.
43     for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i) {
44       Value *OP = MD->getOperand(i);
45       if (!OP || MapValue(OP, VM, ModuleLevelChanges) == OP) continue;
46 
47       // Ok, at least one operand needs remapping.
48       MDNode *Dummy = MDNode::getTemporary(V->getContext(), 0, 0);
49       VM[V] = Dummy;
50       SmallVector<Value*, 4> Elts;
51       Elts.reserve(MD->getNumOperands());
52       for (i = 0; i != e; ++i)
53         Elts.push_back(MD->getOperand(i) ?
54                        MapValue(MD->getOperand(i), VM, ModuleLevelChanges) : 0);
55       MDNode *NewMD = MDNode::get(V->getContext(), Elts.data(), Elts.size());
56       Dummy->replaceAllUsesWith(NewMD);
57       MDNode::deleteTemporary(Dummy);
58       return VM[V] = NewMD;
59     }
60 
61     // No operands needed remapping; keep the identity map.
62     return const_cast<Value*>(V);
63   }
64 
65   Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V));
66   if (C == 0)
67     return 0;
68 
69   if (isa<ConstantInt>(C) || isa<ConstantFP>(C) ||
70       isa<ConstantPointerNull>(C) || isa<ConstantAggregateZero>(C) ||
71       isa<UndefValue>(C))
72     return VMSlot = C;           // Primitive constants map directly
73 
74   if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) {
75     for (User::op_iterator b = CA->op_begin(), i = b, e = CA->op_end();
76          i != e; ++i) {
77       Value *MV = MapValue(*i, VM, ModuleLevelChanges);
78       if (MV != *i) {
79         // This array must contain a reference to a global, make a new array
80         // and return it.
81         //
82         std::vector<Constant*> Values;
83         Values.reserve(CA->getNumOperands());
84         for (User::op_iterator j = b; j != i; ++j)
85           Values.push_back(cast<Constant>(*j));
86         Values.push_back(cast<Constant>(MV));
87         for (++i; i != e; ++i)
88           Values.push_back(cast<Constant>(MapValue(*i, VM,
89                                                    ModuleLevelChanges)));
90         return VM[V] = ConstantArray::get(CA->getType(), Values);
91       }
92     }
93     return VM[V] = C;
94   }
95 
96   if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
97     for (User::op_iterator b = CS->op_begin(), i = b, e = CS->op_end();
98          i != e; ++i) {
99       Value *MV = MapValue(*i, VM, ModuleLevelChanges);
100       if (MV != *i) {
101         // This struct must contain a reference to a global, make a new struct
102         // and return it.
103         //
104         std::vector<Constant*> Values;
105         Values.reserve(CS->getNumOperands());
106         for (User::op_iterator j = b; j != i; ++j)
107           Values.push_back(cast<Constant>(*j));
108         Values.push_back(cast<Constant>(MV));
109         for (++i; i != e; ++i)
110           Values.push_back(cast<Constant>(MapValue(*i, VM,
111                                                    ModuleLevelChanges)));
112         return VM[V] = ConstantStruct::get(CS->getType(), Values);
113       }
114     }
115     return VM[V] = C;
116   }
117 
118   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
119     std::vector<Constant*> Ops;
120     for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
121       Ops.push_back(cast<Constant>(MapValue(*i, VM, ModuleLevelChanges)));
122     return VM[V] = CE->getWithOperands(Ops);
123   }
124 
125   if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
126     for (User::op_iterator b = CV->op_begin(), i = b, e = CV->op_end();
127          i != e; ++i) {
128       Value *MV = MapValue(*i, VM, ModuleLevelChanges);
129       if (MV != *i) {
130         // This vector value must contain a reference to a global, make a new
131         // vector constant and return it.
132         //
133         std::vector<Constant*> Values;
134         Values.reserve(CV->getNumOperands());
135         for (User::op_iterator j = b; j != i; ++j)
136           Values.push_back(cast<Constant>(*j));
137         Values.push_back(cast<Constant>(MV));
138         for (++i; i != e; ++i)
139           Values.push_back(cast<Constant>(MapValue(*i, VM,
140                                                    ModuleLevelChanges)));
141         return VM[V] = ConstantVector::get(Values);
142       }
143     }
144     return VM[V] = C;
145   }
146 
147   BlockAddress *BA = cast<BlockAddress>(C);
148   Function *F = cast<Function>(MapValue(BA->getFunction(), VM,
149                                         ModuleLevelChanges));
150   BasicBlock *BB = cast_or_null<BasicBlock>(MapValue(BA->getBasicBlock(),VM,
151                                              ModuleLevelChanges));
152   return VM[V] = BlockAddress::get(F, BB ? BB : BA->getBasicBlock());
153 }
154 
155 /// RemapInstruction - Convert the instruction operands from referencing the
156 /// current values into those specified by VMap.
157 ///
158 void llvm::RemapInstruction(Instruction *I, ValueToValueMapTy &VMap,
159                             bool ModuleLevelChanges) {
160   // Remap operands.
161   for (User::op_iterator op = I->op_begin(), E = I->op_end(); op != E; ++op) {
162     Value *V = MapValue(*op, VMap, ModuleLevelChanges);
163     assert(V && "Referenced value not in value map!");
164     *op = V;
165   }
166 
167   // Remap attached metadata.
168   SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
169   I->getAllMetadata(MDs);
170   for (SmallVectorImpl<std::pair<unsigned, MDNode *> >::iterator
171        MI = MDs.begin(), ME = MDs.end(); MI != ME; ++MI) {
172     Value *Old = MI->second;
173     Value *New = MapValue(Old, VMap, ModuleLevelChanges);
174     if (New != Old)
175       I->setMetadata(MI->first, cast<MDNode>(New));
176   }
177 }
178