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/Constants.h"
17 #include "llvm/Function.h"
18 #include "llvm/Instructions.h"
19 #include "llvm/Metadata.h"
20 using namespace llvm;
21 
22 // Out of line method to get vtable etc for class.
23 void ValueMapTypeRemapper::Anchor() {}
24 
25 Value *llvm::MapValue(const Value *V, ValueToValueMapTy &VM, RemapFlags Flags,
26                       ValueMapTypeRemapper *TypeMapper) {
27   ValueToValueMapTy::iterator I = VM.find(V);
28 
29   // If the value already exists in the map, use it.
30   if (I != VM.end() && I->second) return I->second;
31 
32   // Global values do not need to be seeded into the VM if they
33   // are using the identity mapping.
34   if (isa<GlobalValue>(V) || isa<InlineAsm>(V) || isa<MDString>(V))
35     return VM[V] = const_cast<Value*>(V);
36 
37   if (const MDNode *MD = dyn_cast<MDNode>(V)) {
38     // If this is a module-level metadata and we know that nothing at the module
39     // level is changing, then use an identity mapping.
40     if (!MD->isFunctionLocal() && (Flags & RF_NoModuleLevelChanges))
41       return VM[V] = const_cast<Value*>(V);
42 
43     // Create a dummy node in case we have a metadata cycle.
44     MDNode *Dummy = MDNode::getTemporary(V->getContext(), ArrayRef<Value*>());
45     VM[V] = Dummy;
46 
47     // Check all operands to see if any need to be remapped.
48     for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i) {
49       Value *OP = MD->getOperand(i);
50       if (OP == 0 || MapValue(OP, VM, Flags, TypeMapper) == OP) continue;
51 
52       // Ok, at least one operand needs remapping.
53       SmallVector<Value*, 4> Elts;
54       Elts.reserve(MD->getNumOperands());
55       for (i = 0; i != e; ++i) {
56         Value *Op = MD->getOperand(i);
57         Elts.push_back(Op ? MapValue(Op, VM, Flags, TypeMapper) : 0);
58       }
59       MDNode *NewMD = MDNode::get(V->getContext(), Elts);
60       Dummy->replaceAllUsesWith(NewMD);
61       VM[V] = NewMD;
62       MDNode::deleteTemporary(Dummy);
63       return NewMD;
64     }
65 
66     VM[V] = const_cast<Value*>(V);
67     MDNode::deleteTemporary(Dummy);
68 
69     // No operands needed remapping.  Use an identity mapping.
70     return const_cast<Value*>(V);
71   }
72 
73   // Okay, this either must be a constant (which may or may not be mappable) or
74   // is something that is not in the mapping table.
75   Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V));
76   if (C == 0)
77     return 0;
78 
79   if (BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
80     Function *F =
81       cast<Function>(MapValue(BA->getFunction(), VM, Flags, TypeMapper));
82     BasicBlock *BB = cast_or_null<BasicBlock>(MapValue(BA->getBasicBlock(), VM,
83                                                        Flags, TypeMapper));
84     return VM[V] = BlockAddress::get(F, BB ? BB : BA->getBasicBlock());
85   }
86 
87   // Otherwise, we have some other constant to remap.  Start by checking to see
88   // if all operands have an identity remapping.
89   unsigned OpNo = 0, NumOperands = C->getNumOperands();
90   Value *Mapped = 0;
91   for (; OpNo != NumOperands; ++OpNo) {
92     Value *Op = C->getOperand(OpNo);
93     Mapped = MapValue(Op, VM, Flags, TypeMapper);
94     if (Mapped != C) break;
95   }
96 
97   // See if the type mapper wants to remap the type as well.
98   Type *NewTy = C->getType();
99   if (TypeMapper)
100     NewTy = TypeMapper->remapType(NewTy);
101 
102   // If the result type and all operands match up, then just insert an identity
103   // mapping.
104   if (OpNo == NumOperands && NewTy == C->getType())
105     return VM[V] = C;
106 
107   // Okay, we need to create a new constant.  We've already processed some or
108   // all of the operands, set them all up now.
109   SmallVector<Constant*, 8> Ops;
110   Ops.reserve(NumOperands);
111   for (unsigned j = 0; j != OpNo; ++j)
112     Ops.push_back(cast<Constant>(C->getOperand(j)));
113 
114   // If one of the operands mismatch, push it and the other mapped operands.
115   if (OpNo != NumOperands) {
116     Ops.push_back(cast<Constant>(Mapped));
117 
118     // Map the rest of the operands that aren't processed yet.
119     for (++OpNo; OpNo != NumOperands; ++OpNo)
120       Ops.push_back(MapValue(cast<Constant>(C->getOperand(OpNo)), VM,
121                              Flags, TypeMapper));
122   }
123 
124   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
125     return VM[V] = CE->getWithOperands(Ops, NewTy);
126   if (isa<ConstantArray>(C))
127     return VM[V] = ConstantArray::get(cast<ArrayType>(NewTy), Ops);
128   if (isa<ConstantStruct>(C))
129     return VM[V] = ConstantStruct::get(cast<StructType>(NewTy), Ops);
130   if (isa<ConstantVector>(C))
131     return VM[V] = ConstantVector::get(Ops);
132   // If this is a no-operand constant, it must be because the type was remapped.
133   if (isa<UndefValue>(C))
134     return VM[V] = UndefValue::get(NewTy);
135   if (isa<ConstantAggregateZero>(C))
136     return VM[V] = ConstantAggregateZero::get(NewTy);
137   assert(isa<ConstantPointerNull>(C));
138   return VM[V] = ConstantPointerNull::get(cast<PointerType>(NewTy));
139 }
140 
141 /// RemapInstruction - Convert the instruction operands from referencing the
142 /// current values into those specified by VMap.
143 ///
144 void llvm::RemapInstruction(Instruction *I, ValueToValueMapTy &VMap,
145                             RemapFlags Flags, ValueMapTypeRemapper *TypeMapper){
146   // Remap operands.
147   for (User::op_iterator op = I->op_begin(), E = I->op_end(); op != E; ++op) {
148     Value *V = MapValue(*op, VMap, Flags, TypeMapper);
149     // If we aren't ignoring missing entries, assert that something happened.
150     if (V != 0)
151       *op = V;
152     else
153       assert((Flags & RF_IgnoreMissingEntries) &&
154              "Referenced value not in value map!");
155   }
156 
157   // Remap phi nodes' incoming blocks.
158   if (PHINode *PN = dyn_cast<PHINode>(I)) {
159     for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
160       Value *V = MapValue(PN->getIncomingBlock(i), VMap, Flags);
161       // If we aren't ignoring missing entries, assert that something happened.
162       if (V != 0)
163         PN->setIncomingBlock(i, cast<BasicBlock>(V));
164       else
165         assert((Flags & RF_IgnoreMissingEntries) &&
166                "Referenced block not in value map!");
167     }
168   }
169 
170   // Remap attached metadata.
171   SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
172   I->getAllMetadata(MDs);
173   for (SmallVectorImpl<std::pair<unsigned, MDNode *> >::iterator
174        MI = MDs.begin(), ME = MDs.end(); MI != ME; ++MI) {
175     MDNode *Old = MI->second;
176     MDNode *New = MapValue(Old, VMap, Flags, TypeMapper);
177     if (New != Old)
178       I->setMetadata(MI->first, New);
179   }
180 
181   // If the instruction's type is being remapped, do so now.
182   if (TypeMapper)
183     I->mutateType(TypeMapper->remapType(I->getType()));
184 }
185