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      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/IR/Constants.h"
     17 #include "llvm/IR/Function.h"
     18 #include "llvm/IR/InlineAsm.h"
     19 #include "llvm/IR/Instructions.h"
     20 #include "llvm/IR/Metadata.h"
     21 using namespace llvm;
     22 
     23 // Out of line method to get vtable etc for class.
     24 void ValueMapTypeRemapper::anchor() {}
     25 void ValueMaterializer::anchor() {}
     26 
     27 Value *llvm::MapValue(const Value *V, ValueToValueMapTy &VM, RemapFlags Flags,
     28                       ValueMapTypeRemapper *TypeMapper,
     29                       ValueMaterializer *Materializer) {
     30   ValueToValueMapTy::iterator I = VM.find(V);
     31 
     32   // If the value already exists in the map, use it.
     33   if (I != VM.end() && I->second) return I->second;
     34 
     35   // If we have a materializer and it can materialize a value, use that.
     36   if (Materializer) {
     37     if (Value *NewV = Materializer->materializeValueFor(const_cast<Value*>(V)))
     38       return VM[V] = NewV;
     39   }
     40 
     41   // Global values do not need to be seeded into the VM if they
     42   // are using the identity mapping.
     43   if (isa<GlobalValue>(V) || isa<MDString>(V))
     44     return VM[V] = const_cast<Value*>(V);
     45 
     46   if (const InlineAsm *IA = dyn_cast<InlineAsm>(V)) {
     47     // Inline asm may need *type* remapping.
     48     FunctionType *NewTy = IA->getFunctionType();
     49     if (TypeMapper) {
     50       NewTy = cast<FunctionType>(TypeMapper->remapType(NewTy));
     51 
     52       if (NewTy != IA->getFunctionType())
     53         V = InlineAsm::get(NewTy, IA->getAsmString(), IA->getConstraintString(),
     54                            IA->hasSideEffects(), IA->isAlignStack());
     55     }
     56 
     57     return VM[V] = const_cast<Value*>(V);
     58   }
     59 
     60 
     61   if (const MDNode *MD = dyn_cast<MDNode>(V)) {
     62     // If this is a module-level metadata and we know that nothing at the module
     63     // level is changing, then use an identity mapping.
     64     if (!MD->isFunctionLocal() && (Flags & RF_NoModuleLevelChanges))
     65       return VM[V] = const_cast<Value*>(V);
     66 
     67     // Create a dummy node in case we have a metadata cycle.
     68     MDNode *Dummy = MDNode::getTemporary(V->getContext(), None);
     69     VM[V] = Dummy;
     70 
     71     // Check all operands to see if any need to be remapped.
     72     for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i) {
     73       Value *OP = MD->getOperand(i);
     74       if (!OP) continue;
     75       Value *Mapped_OP = MapValue(OP, VM, Flags, TypeMapper, Materializer);
     76       // Use identity map if Mapped_Op is null and we can ignore missing
     77       // entries.
     78       if (Mapped_OP == OP ||
     79           (Mapped_OP == nullptr && (Flags & RF_IgnoreMissingEntries)))
     80         continue;
     81 
     82       // Ok, at least one operand needs remapping.
     83       SmallVector<Value*, 4> Elts;
     84       Elts.reserve(MD->getNumOperands());
     85       for (i = 0; i != e; ++i) {
     86         Value *Op = MD->getOperand(i);
     87         if (!Op)
     88           Elts.push_back(nullptr);
     89         else {
     90           Value *Mapped_Op = MapValue(Op, VM, Flags, TypeMapper, Materializer);
     91           // Use identity map if Mapped_Op is null and we can ignore missing
     92           // entries.
     93           if (Mapped_Op == nullptr && (Flags & RF_IgnoreMissingEntries))
     94             Mapped_Op = Op;
     95           Elts.push_back(Mapped_Op);
     96         }
     97       }
     98       MDNode *NewMD = MDNode::get(V->getContext(), Elts);
     99       Dummy->replaceAllUsesWith(NewMD);
    100       VM[V] = NewMD;
    101       MDNode::deleteTemporary(Dummy);
    102       return NewMD;
    103     }
    104 
    105     VM[V] = const_cast<Value*>(V);
    106     MDNode::deleteTemporary(Dummy);
    107 
    108     // No operands needed remapping.  Use an identity mapping.
    109     return const_cast<Value*>(V);
    110   }
    111 
    112   // Okay, this either must be a constant (which may or may not be mappable) or
    113   // is something that is not in the mapping table.
    114   Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V));
    115   if (!C)
    116     return nullptr;
    117 
    118   if (BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
    119     Function *F =
    120       cast<Function>(MapValue(BA->getFunction(), VM, Flags, TypeMapper, Materializer));
    121     BasicBlock *BB = cast_or_null<BasicBlock>(MapValue(BA->getBasicBlock(), VM,
    122                                                        Flags, TypeMapper, Materializer));
    123     return VM[V] = BlockAddress::get(F, BB ? BB : BA->getBasicBlock());
    124   }
    125 
    126   // Otherwise, we have some other constant to remap.  Start by checking to see
    127   // if all operands have an identity remapping.
    128   unsigned OpNo = 0, NumOperands = C->getNumOperands();
    129   Value *Mapped = nullptr;
    130   for (; OpNo != NumOperands; ++OpNo) {
    131     Value *Op = C->getOperand(OpNo);
    132     Mapped = MapValue(Op, VM, Flags, TypeMapper, Materializer);
    133     if (Mapped != C) break;
    134   }
    135 
    136   // See if the type mapper wants to remap the type as well.
    137   Type *NewTy = C->getType();
    138   if (TypeMapper)
    139     NewTy = TypeMapper->remapType(NewTy);
    140 
    141   // If the result type and all operands match up, then just insert an identity
    142   // mapping.
    143   if (OpNo == NumOperands && NewTy == C->getType())
    144     return VM[V] = C;
    145 
    146   // Okay, we need to create a new constant.  We've already processed some or
    147   // all of the operands, set them all up now.
    148   SmallVector<Constant*, 8> Ops;
    149   Ops.reserve(NumOperands);
    150   for (unsigned j = 0; j != OpNo; ++j)
    151     Ops.push_back(cast<Constant>(C->getOperand(j)));
    152 
    153   // If one of the operands mismatch, push it and the other mapped operands.
    154   if (OpNo != NumOperands) {
    155     Ops.push_back(cast<Constant>(Mapped));
    156 
    157     // Map the rest of the operands that aren't processed yet.
    158     for (++OpNo; OpNo != NumOperands; ++OpNo)
    159       Ops.push_back(MapValue(cast<Constant>(C->getOperand(OpNo)), VM,
    160                              Flags, TypeMapper, Materializer));
    161   }
    162 
    163   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
    164     return VM[V] = CE->getWithOperands(Ops, NewTy);
    165   if (isa<ConstantArray>(C))
    166     return VM[V] = ConstantArray::get(cast<ArrayType>(NewTy), Ops);
    167   if (isa<ConstantStruct>(C))
    168     return VM[V] = ConstantStruct::get(cast<StructType>(NewTy), Ops);
    169   if (isa<ConstantVector>(C))
    170     return VM[V] = ConstantVector::get(Ops);
    171   // If this is a no-operand constant, it must be because the type was remapped.
    172   if (isa<UndefValue>(C))
    173     return VM[V] = UndefValue::get(NewTy);
    174   if (isa<ConstantAggregateZero>(C))
    175     return VM[V] = ConstantAggregateZero::get(NewTy);
    176   assert(isa<ConstantPointerNull>(C));
    177   return VM[V] = ConstantPointerNull::get(cast<PointerType>(NewTy));
    178 }
    179 
    180 /// RemapInstruction - Convert the instruction operands from referencing the
    181 /// current values into those specified by VMap.
    182 ///
    183 void llvm::RemapInstruction(Instruction *I, ValueToValueMapTy &VMap,
    184                             RemapFlags Flags, ValueMapTypeRemapper *TypeMapper,
    185                             ValueMaterializer *Materializer){
    186   // Remap operands.
    187   for (User::op_iterator op = I->op_begin(), E = I->op_end(); op != E; ++op) {
    188     Value *V = MapValue(*op, VMap, Flags, TypeMapper, Materializer);
    189     // If we aren't ignoring missing entries, assert that something happened.
    190     if (V)
    191       *op = V;
    192     else
    193       assert((Flags & RF_IgnoreMissingEntries) &&
    194              "Referenced value not in value map!");
    195   }
    196 
    197   // Remap phi nodes' incoming blocks.
    198   if (PHINode *PN = dyn_cast<PHINode>(I)) {
    199     for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
    200       Value *V = MapValue(PN->getIncomingBlock(i), VMap, Flags);
    201       // If we aren't ignoring missing entries, assert that something happened.
    202       if (V)
    203         PN->setIncomingBlock(i, cast<BasicBlock>(V));
    204       else
    205         assert((Flags & RF_IgnoreMissingEntries) &&
    206                "Referenced block not in value map!");
    207     }
    208   }
    209 
    210   // Remap attached metadata.
    211   SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
    212   I->getAllMetadata(MDs);
    213   for (SmallVectorImpl<std::pair<unsigned, MDNode *> >::iterator
    214        MI = MDs.begin(), ME = MDs.end(); MI != ME; ++MI) {
    215     MDNode *Old = MI->second;
    216     MDNode *New = MapValue(Old, VMap, Flags, TypeMapper, Materializer);
    217     if (New != Old)
    218       I->setMetadata(MI->first, New);
    219   }
    220 
    221   // If the instruction's type is being remapped, do so now.
    222   if (TypeMapper)
    223     I->mutateType(TypeMapper->remapType(I->getType()));
    224 }
    225