ValueMapper.cpp revision ec9186bcf975c9ffa3ec7ca97867f0ec6eb55115 
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"
21using namespace llvm;
22
23Value *llvm::MapValue(const Value *V, ValueToValueMapTy &VM,
24                      RemapFlags Flags) {
25  ValueToValueMapTy::iterator I = VM.find(V);
26
27  // If the value already exists in the map, use it.
28  if (I != VM.end() && I->second) return I->second;
29
30  // Global values do not need to be seeded into the VM if they
31  // are using the identity mapping.
32  if (isa<GlobalValue>(V) || isa<InlineAsm>(V) || isa<MDString>(V))
33    return VM[V] = const_cast<Value*>(V);
34
35  if (const MDNode *MD = dyn_cast<MDNode>(V)) {
36    // If this is a module-level metadata and we know that nothing at the module
37    // level is changing, then use an identity mapping.
38    if (!MD->isFunctionLocal() && (Flags & RF_NoModuleLevelChanges))
39      return VM[V] = const_cast<Value*>(V);
40
41    // Create a dummy node in case we have a metadata cycle.
42    MDNode *Dummy = MDNode::getTemporary(V->getContext(), ArrayRef<Value*>());
43    VM[V] = Dummy;
44
45    // Check all operands to see if any need to be remapped.
46    for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i) {
47      Value *OP = MD->getOperand(i);
48      if (OP == 0 || MapValue(OP, VM, Flags) == OP) continue;
49
50      // Ok, at least one operand needs remapping.
51      SmallVector<Value*, 4> Elts;
52      Elts.reserve(MD->getNumOperands());
53      for (i = 0; i != e; ++i) {
54        Value *Op = MD->getOperand(i);
55        Elts.push_back(Op ? MapValue(Op, VM, Flags) : 0);
56      }
57      MDNode *NewMD = MDNode::get(V->getContext(), Elts);
58      Dummy->replaceAllUsesWith(NewMD);
59      VM[V] = NewMD;
60      MDNode::deleteTemporary(Dummy);
61      return NewMD;
62    }
63
64    VM[V] = const_cast<Value*>(V);
65    MDNode::deleteTemporary(Dummy);
66
67    // No operands needed remapping.  Use an identity mapping.
68    return const_cast<Value*>(V);
69  }
70
71  // Okay, this either must be a constant (which may or may not be mappable) or
72  // is something that is not in the mapping table.
73  Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V));
74  if (C == 0)
75    return 0;
76
77  if (BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
78    Function *F = cast<Function>(MapValue(BA->getFunction(), VM, Flags));
79    BasicBlock *BB = cast_or_null<BasicBlock>(MapValue(BA->getBasicBlock(), VM,
80                                                       Flags));
81    return VM[V] = BlockAddress::get(F, BB ? BB : BA->getBasicBlock());
82  }
83
84  for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
85    Value *Op = C->getOperand(i);
86    Value *Mapped = MapValue(Op, VM, Flags);
87    if (Mapped == C) continue;
88
89    // Okay, the operands don't all match.  We've already processed some or all
90    // of the operands, set them up now.
91    std::vector<Constant*> Ops;
92    Ops.reserve(C->getNumOperands());
93    for (unsigned j = 0; j != i; ++j)
94      Ops.push_back(cast<Constant>(C->getOperand(i)));
95    Ops.push_back(cast<Constant>(Mapped));
96
97    // Map the rest of the operands that aren't processed yet.
98    for (++i; i != e; ++i)
99      Ops.push_back(cast<Constant>(MapValue(C->getOperand(i), VM, Flags)));
100
101    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
102      return VM[V] = CE->getWithOperands(Ops);
103    if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
104      return VM[V] = ConstantArray::get(CA->getType(), Ops);
105    if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C))
106      return VM[V] = ConstantStruct::get(CS->getType(), Ops);
107    assert(isa<ConstantVector>(C) && "Unknown mapped constant type");
108    return VM[V] = ConstantVector::get(Ops);
109  }
110
111  // If we reach here, all of the operands of the constant match.
112  return VM[V] = C;
113}
114
115/// RemapInstruction - Convert the instruction operands from referencing the
116/// current values into those specified by VMap.
117///
118void llvm::RemapInstruction(Instruction *I, ValueToValueMapTy &VMap,
119                            RemapFlags Flags) {
120  // Remap operands.
121  for (User::op_iterator op = I->op_begin(), E = I->op_end(); op != E; ++op) {
122    Value *V = MapValue(*op, VMap, Flags);
123    // If we aren't ignoring missing entries, assert that something happened.
124    if (V != 0)
125      *op = V;
126    else
127      assert((Flags & RF_IgnoreMissingEntries) &&
128             "Referenced value not in value map!");
129  }
130
131  // Remap attached metadata.
132  SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
133  I->getAllMetadata(MDs);
134  for (SmallVectorImpl<std::pair<unsigned, MDNode *> >::iterator
135       MI = MDs.begin(), ME = MDs.end(); MI != ME; ++MI) {
136    Value *Old = MI->second;
137    Value *New = MapValue(Old, VMap, Flags);
138    if (New != Old)
139      I->setMetadata(MI->first, cast<MDNode>(New));
140  }
141}
142