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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/Constants.h"
     17 #include "llvm/Function.h"
     18 #include "llvm/InlineAsm.h"
     19 #include "llvm/Instructions.h"
     20 #include "llvm/Metadata.h"
     21 using namespace llvm;
     22 
     23 // Out of line method to get vtable etc for class.
     24 void ValueMapTypeRemapper::Anchor() {}
     25 
     26 Value *llvm::MapValue(const Value *V, ValueToValueMapTy &VM, RemapFlags Flags,
     27                       ValueMapTypeRemapper *TypeMapper) {
     28   ValueToValueMapTy::iterator I = VM.find(V);
     29 
     30   // If the value already exists in the map, use it.
     31   if (I != VM.end() && I->second) return I->second;
     32 
     33   // Global values do not need to be seeded into the VM if they
     34   // are using the identity mapping.
     35   if (isa<GlobalValue>(V) || isa<MDString>(V))
     36     return VM[V] = const_cast<Value*>(V);
     37 
     38   if (const InlineAsm *IA = dyn_cast<InlineAsm>(V)) {
     39     // Inline asm may need *type* remapping.
     40     FunctionType *NewTy = IA->getFunctionType();
     41     if (TypeMapper) {
     42       NewTy = cast<FunctionType>(TypeMapper->remapType(NewTy));
     43 
     44       if (NewTy != IA->getFunctionType())
     45         V = InlineAsm::get(NewTy, IA->getAsmString(), IA->getConstraintString(),
     46                            IA->hasSideEffects(), IA->isAlignStack());
     47     }
     48 
     49     return VM[V] = const_cast<Value*>(V);
     50   }
     51 
     52 
     53   if (const MDNode *MD = dyn_cast<MDNode>(V)) {
     54     // If this is a module-level metadata and we know that nothing at the module
     55     // level is changing, then use an identity mapping.
     56     if (!MD->isFunctionLocal() && (Flags & RF_NoModuleLevelChanges))
     57       return VM[V] = const_cast<Value*>(V);
     58 
     59     // Create a dummy node in case we have a metadata cycle.
     60     MDNode *Dummy = MDNode::getTemporary(V->getContext(), ArrayRef<Value*>());
     61     VM[V] = Dummy;
     62 
     63     // Check all operands to see if any need to be remapped.
     64     for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i) {
     65       Value *OP = MD->getOperand(i);
     66       if (OP == 0 || MapValue(OP, VM, Flags, TypeMapper) == OP) continue;
     67 
     68       // Ok, at least one operand needs remapping.
     69       SmallVector<Value*, 4> Elts;
     70       Elts.reserve(MD->getNumOperands());
     71       for (i = 0; i != e; ++i) {
     72         Value *Op = MD->getOperand(i);
     73         Elts.push_back(Op ? MapValue(Op, VM, Flags, TypeMapper) : 0);
     74       }
     75       MDNode *NewMD = MDNode::get(V->getContext(), Elts);
     76       Dummy->replaceAllUsesWith(NewMD);
     77       VM[V] = NewMD;
     78       MDNode::deleteTemporary(Dummy);
     79       return NewMD;
     80     }
     81 
     82     VM[V] = const_cast<Value*>(V);
     83     MDNode::deleteTemporary(Dummy);
     84 
     85     // No operands needed remapping.  Use an identity mapping.
     86     return const_cast<Value*>(V);
     87   }
     88 
     89   // Okay, this either must be a constant (which may or may not be mappable) or
     90   // is something that is not in the mapping table.
     91   Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V));
     92   if (C == 0)
     93     return 0;
     94 
     95   if (BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
     96     Function *F =
     97       cast<Function>(MapValue(BA->getFunction(), VM, Flags, TypeMapper));
     98     BasicBlock *BB = cast_or_null<BasicBlock>(MapValue(BA->getBasicBlock(), VM,
     99                                                        Flags, TypeMapper));
    100     return VM[V] = BlockAddress::get(F, BB ? BB : BA->getBasicBlock());
    101   }
    102 
    103   // Otherwise, we have some other constant to remap.  Start by checking to see
    104   // if all operands have an identity remapping.
    105   unsigned OpNo = 0, NumOperands = C->getNumOperands();
    106   Value *Mapped = 0;
    107   for (; OpNo != NumOperands; ++OpNo) {
    108     Value *Op = C->getOperand(OpNo);
    109     Mapped = MapValue(Op, VM, Flags, TypeMapper);
    110     if (Mapped != C) break;
    111   }
    112 
    113   // See if the type mapper wants to remap the type as well.
    114   Type *NewTy = C->getType();
    115   if (TypeMapper)
    116     NewTy = TypeMapper->remapType(NewTy);
    117 
    118   // If the result type and all operands match up, then just insert an identity
    119   // mapping.
    120   if (OpNo == NumOperands && NewTy == C->getType())
    121     return VM[V] = C;
    122 
    123   // Okay, we need to create a new constant.  We've already processed some or
    124   // all of the operands, set them all up now.
    125   SmallVector<Constant*, 8> Ops;
    126   Ops.reserve(NumOperands);
    127   for (unsigned j = 0; j != OpNo; ++j)
    128     Ops.push_back(cast<Constant>(C->getOperand(j)));
    129 
    130   // If one of the operands mismatch, push it and the other mapped operands.
    131   if (OpNo != NumOperands) {
    132     Ops.push_back(cast<Constant>(Mapped));
    133 
    134     // Map the rest of the operands that aren't processed yet.
    135     for (++OpNo; OpNo != NumOperands; ++OpNo)
    136       Ops.push_back(MapValue(cast<Constant>(C->getOperand(OpNo)), VM,
    137                              Flags, TypeMapper));
    138   }
    139 
    140   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
    141     return VM[V] = CE->getWithOperands(Ops, NewTy);
    142   if (isa<ConstantArray>(C))
    143     return VM[V] = ConstantArray::get(cast<ArrayType>(NewTy), Ops);
    144   if (isa<ConstantStruct>(C))
    145     return VM[V] = ConstantStruct::get(cast<StructType>(NewTy), Ops);
    146   if (isa<ConstantVector>(C))
    147     return VM[V] = ConstantVector::get(Ops);
    148   // If this is a no-operand constant, it must be because the type was remapped.
    149   if (isa<UndefValue>(C))
    150     return VM[V] = UndefValue::get(NewTy);
    151   if (isa<ConstantAggregateZero>(C))
    152     return VM[V] = ConstantAggregateZero::get(NewTy);
    153   assert(isa<ConstantPointerNull>(C));
    154   return VM[V] = ConstantPointerNull::get(cast<PointerType>(NewTy));
    155 }
    156 
    157 /// RemapInstruction - Convert the instruction operands from referencing the
    158 /// current values into those specified by VMap.
    159 ///
    160 void llvm::RemapInstruction(Instruction *I, ValueToValueMapTy &VMap,
    161                             RemapFlags Flags, ValueMapTypeRemapper *TypeMapper){
    162   // Remap operands.
    163   for (User::op_iterator op = I->op_begin(), E = I->op_end(); op != E; ++op) {
    164     Value *V = MapValue(*op, VMap, Flags, TypeMapper);
    165     // If we aren't ignoring missing entries, assert that something happened.
    166     if (V != 0)
    167       *op = V;
    168     else
    169       assert((Flags & RF_IgnoreMissingEntries) &&
    170              "Referenced value not in value map!");
    171   }
    172 
    173   // Remap phi nodes' incoming blocks.
    174   if (PHINode *PN = dyn_cast<PHINode>(I)) {
    175     for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
    176       Value *V = MapValue(PN->getIncomingBlock(i), VMap, Flags);
    177       // If we aren't ignoring missing entries, assert that something happened.
    178       if (V != 0)
    179         PN->setIncomingBlock(i, cast<BasicBlock>(V));
    180       else
    181         assert((Flags & RF_IgnoreMissingEntries) &&
    182                "Referenced block not in value map!");
    183     }
    184   }
    185 
    186   // Remap attached metadata.
    187   SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
    188   I->getAllMetadata(MDs);
    189   for (SmallVectorImpl<std::pair<unsigned, MDNode *> >::iterator
    190        MI = MDs.begin(), ME = MDs.end(); MI != ME; ++MI) {
    191     MDNode *Old = MI->second;
    192     MDNode *New = MapValue(Old, VMap, Flags, TypeMapper);
    193     if (New != Old)
    194       I->setMetadata(MI->first, New);
    195   }
    196 
    197   // If the instruction's type is being remapped, do so now.
    198   if (TypeMapper)
    199     I->mutateType(TypeMapper->remapType(I->getType()));
    200 }
    201