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Diffstat (limited to 'release_23/lib/Linker/LinkModules.cpp')
| -rw-r--r-- | release_23/lib/Linker/LinkModules.cpp | 1224 |
1 files changed, 0 insertions, 1224 deletions
diff --git a/release_23/lib/Linker/LinkModules.cpp b/release_23/lib/Linker/LinkModules.cpp deleted file mode 100644 index 57df01495b7c..000000000000 --- a/release_23/lib/Linker/LinkModules.cpp +++ /dev/null @@ -1,1224 +0,0 @@ -//===- lib/Linker/LinkModules.cpp - Module Linker Implementation ----------===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// This file implements the LLVM module linker. -// -// Specifically, this: -// * Merges global variables between the two modules -// * Uninit + Uninit = Init, Init + Uninit = Init, Init + Init = Error if != -// * Merges functions between two modules -// -//===----------------------------------------------------------------------===// - -#include "llvm/Linker.h" -#include "llvm/Constants.h" -#include "llvm/DerivedTypes.h" -#include "llvm/Module.h" -#include "llvm/TypeSymbolTable.h" -#include "llvm/ValueSymbolTable.h" -#include "llvm/Instructions.h" -#include "llvm/Assembly/Writer.h" -#include "llvm/Support/Streams.h" -#include "llvm/System/Path.h" -#include <sstream> -using namespace llvm; - -// Error - Simple wrapper function to conditionally assign to E and return true. -// This just makes error return conditions a little bit simpler... -static inline bool Error(std::string *E, const std::string &Message) { - if (E) *E = Message; - return true; -} - -// ToStr - Simple wrapper function to convert a type to a string. -static std::string ToStr(const Type *Ty, const Module *M) { - std::ostringstream OS; - WriteTypeSymbolic(OS, Ty, M); - return OS.str(); -} - -// -// Function: ResolveTypes() -// -// Description: -// Attempt to link the two specified types together. -// -// Inputs: -// DestTy - The type to which we wish to resolve. -// SrcTy - The original type which we want to resolve. -// Name - The name of the type. -// -// Outputs: -// DestST - The symbol table in which the new type should be placed. -// -// Return value: -// true - There is an error and the types cannot yet be linked. -// false - No errors. -// -static bool ResolveTypes(const Type *DestTy, const Type *SrcTy, - TypeSymbolTable *DestST, const std::string &Name) { - if (DestTy == SrcTy) return false; // If already equal, noop - - // Does the type already exist in the module? - if (DestTy && !isa<OpaqueType>(DestTy)) { // Yup, the type already exists... - if (const OpaqueType *OT = dyn_cast<OpaqueType>(SrcTy)) { - const_cast<OpaqueType*>(OT)->refineAbstractTypeTo(DestTy); - } else { - return true; // Cannot link types... neither is opaque and not-equal - } - } else { // Type not in dest module. Add it now. - if (DestTy) // Type _is_ in module, just opaque... - const_cast<OpaqueType*>(cast<OpaqueType>(DestTy)) - ->refineAbstractTypeTo(SrcTy); - else if (!Name.empty()) - DestST->insert(Name, const_cast<Type*>(SrcTy)); - } - return false; -} - -static const FunctionType *getFT(const PATypeHolder &TH) { - return cast<FunctionType>(TH.get()); -} -static const StructType *getST(const PATypeHolder &TH) { - return cast<StructType>(TH.get()); -} - -// RecursiveResolveTypes - This is just like ResolveTypes, except that it -// recurses down into derived types, merging the used types if the parent types -// are compatible. -static bool RecursiveResolveTypesI(const PATypeHolder &DestTy, - const PATypeHolder &SrcTy, - TypeSymbolTable *DestST, - const std::string &Name, - std::vector<std::pair<PATypeHolder, PATypeHolder> > &Pointers) { - const Type *SrcTyT = SrcTy.get(); - const Type *DestTyT = DestTy.get(); - if (DestTyT == SrcTyT) return false; // If already equal, noop - - // If we found our opaque type, resolve it now! - if (isa<OpaqueType>(DestTyT) || isa<OpaqueType>(SrcTyT)) - return ResolveTypes(DestTyT, SrcTyT, DestST, Name); - - // Two types cannot be resolved together if they are of different primitive - // type. For example, we cannot resolve an int to a float. - if (DestTyT->getTypeID() != SrcTyT->getTypeID()) return true; - - // Otherwise, resolve the used type used by this derived type... - switch (DestTyT->getTypeID()) { - case Type::IntegerTyID: { - if (cast<IntegerType>(DestTyT)->getBitWidth() != - cast<IntegerType>(SrcTyT)->getBitWidth()) - return true; - return false; - } - case Type::FunctionTyID: { - if (cast<FunctionType>(DestTyT)->isVarArg() != - cast<FunctionType>(SrcTyT)->isVarArg() || - cast<FunctionType>(DestTyT)->getNumContainedTypes() != - cast<FunctionType>(SrcTyT)->getNumContainedTypes()) - return true; - for (unsigned i = 0, e = getFT(DestTy)->getNumContainedTypes(); i != e; ++i) - if (RecursiveResolveTypesI(getFT(DestTy)->getContainedType(i), - getFT(SrcTy)->getContainedType(i), DestST, "", - Pointers)) - return true; - return false; - } - case Type::StructTyID: { - if (getST(DestTy)->getNumContainedTypes() != - getST(SrcTy)->getNumContainedTypes()) return 1; - for (unsigned i = 0, e = getST(DestTy)->getNumContainedTypes(); i != e; ++i) - if (RecursiveResolveTypesI(getST(DestTy)->getContainedType(i), - getST(SrcTy)->getContainedType(i), DestST, "", - Pointers)) - return true; - return false; - } - case Type::ArrayTyID: { - const ArrayType *DAT = cast<ArrayType>(DestTy.get()); - const ArrayType *SAT = cast<ArrayType>(SrcTy.get()); - if (DAT->getNumElements() != SAT->getNumElements()) return true; - return RecursiveResolveTypesI(DAT->getElementType(), SAT->getElementType(), - DestST, "", Pointers); - } - case Type::PointerTyID: { - // If this is a pointer type, check to see if we have already seen it. If - // so, we are in a recursive branch. Cut off the search now. We cannot use - // an associative container for this search, because the type pointers (keys - // in the container) change whenever types get resolved... - for (unsigned i = 0, e = Pointers.size(); i != e; ++i) - if (Pointers[i].first == DestTy) - return Pointers[i].second != SrcTy; - - // Otherwise, add the current pointers to the vector to stop recursion on - // this pair. - Pointers.push_back(std::make_pair(DestTyT, SrcTyT)); - bool Result = - RecursiveResolveTypesI(cast<PointerType>(DestTy.get())->getElementType(), - cast<PointerType>(SrcTy.get())->getElementType(), - DestST, "", Pointers); - Pointers.pop_back(); - return Result; - } - default: assert(0 && "Unexpected type!"); return true; - } -} - -static bool RecursiveResolveTypes(const PATypeHolder &DestTy, - const PATypeHolder &SrcTy, - TypeSymbolTable *DestST, - const std::string &Name){ - std::vector<std::pair<PATypeHolder, PATypeHolder> > PointerTypes; - return RecursiveResolveTypesI(DestTy, SrcTy, DestST, Name, PointerTypes); -} - - -// LinkTypes - Go through the symbol table of the Src module and see if any -// types are named in the src module that are not named in the Dst module. -// Make sure there are no type name conflicts. -static bool LinkTypes(Module *Dest, const Module *Src, std::string *Err) { - TypeSymbolTable *DestST = &Dest->getTypeSymbolTable(); - const TypeSymbolTable *SrcST = &Src->getTypeSymbolTable(); - - // Look for a type plane for Type's... - TypeSymbolTable::const_iterator TI = SrcST->begin(); - TypeSymbolTable::const_iterator TE = SrcST->end(); - if (TI == TE) return false; // No named types, do nothing. - - // Some types cannot be resolved immediately because they depend on other - // types being resolved to each other first. This contains a list of types we - // are waiting to recheck. - std::vector<std::string> DelayedTypesToResolve; - - for ( ; TI != TE; ++TI ) { - const std::string &Name = TI->first; - const Type *RHS = TI->second; - - // Check to see if this type name is already in the dest module... - Type *Entry = DestST->lookup(Name); - - if (ResolveTypes(Entry, RHS, DestST, Name)) { - // They look different, save the types 'till later to resolve. - DelayedTypesToResolve.push_back(Name); - } - } - - // Iteratively resolve types while we can... - while (!DelayedTypesToResolve.empty()) { - // Loop over all of the types, attempting to resolve them if possible... - unsigned OldSize = DelayedTypesToResolve.size(); - - // Try direct resolution by name... - for (unsigned i = 0; i != DelayedTypesToResolve.size(); ++i) { - const std::string &Name = DelayedTypesToResolve[i]; - Type *T1 = SrcST->lookup(Name); - Type *T2 = DestST->lookup(Name); - if (!ResolveTypes(T2, T1, DestST, Name)) { - // We are making progress! - DelayedTypesToResolve.erase(DelayedTypesToResolve.begin()+i); - --i; - } - } - - // Did we not eliminate any types? - if (DelayedTypesToResolve.size() == OldSize) { - // Attempt to resolve subelements of types. This allows us to merge these - // two types: { int* } and { opaque* } - for (unsigned i = 0, e = DelayedTypesToResolve.size(); i != e; ++i) { - const std::string &Name = DelayedTypesToResolve[i]; - PATypeHolder T1(SrcST->lookup(Name)); - PATypeHolder T2(DestST->lookup(Name)); - - if (!RecursiveResolveTypes(T2, T1, DestST, Name)) { - // We are making progress! - DelayedTypesToResolve.erase(DelayedTypesToResolve.begin()+i); - - // Go back to the main loop, perhaps we can resolve directly by name - // now... - break; - } - } - - // If we STILL cannot resolve the types, then there is something wrong. - if (DelayedTypesToResolve.size() == OldSize) { - // Remove the symbol name from the destination. - DelayedTypesToResolve.pop_back(); - } - } - } - - - return false; -} - -static void PrintMap(const std::map<const Value*, Value*> &M) { - for (std::map<const Value*, Value*>::const_iterator I = M.begin(), E =M.end(); - I != E; ++I) { - cerr << " Fr: " << (void*)I->first << " "; - I->first->dump(); - cerr << " To: " << (void*)I->second << " "; - I->second->dump(); - cerr << "\n"; - } -} - - -// RemapOperand - Use ValueMap to convert constants from one module to another. -static Value *RemapOperand(const Value *In, - std::map<const Value*, Value*> &ValueMap) { - std::map<const Value*,Value*>::const_iterator I = ValueMap.find(In); - if (I != ValueMap.end()) - return I->second; - - // Check to see if it's a constant that we are interested in transforming. - Value *Result = 0; - if (const Constant *CPV = dyn_cast<Constant>(In)) { - if ((!isa<DerivedType>(CPV->getType()) && !isa<ConstantExpr>(CPV)) || - isa<ConstantInt>(CPV) || isa<ConstantAggregateZero>(CPV)) - return const_cast<Constant*>(CPV); // Simple constants stay identical. - - if (const ConstantArray *CPA = dyn_cast<ConstantArray>(CPV)) { - std::vector<Constant*> Operands(CPA->getNumOperands()); - for (unsigned i = 0, e = CPA->getNumOperands(); i != e; ++i) - Operands[i] =cast<Constant>(RemapOperand(CPA->getOperand(i), ValueMap)); - Result = ConstantArray::get(cast<ArrayType>(CPA->getType()), Operands); - } else if (const ConstantStruct *CPS = dyn_cast<ConstantStruct>(CPV)) { - std::vector<Constant*> Operands(CPS->getNumOperands()); - for (unsigned i = 0, e = CPS->getNumOperands(); i != e; ++i) - Operands[i] =cast<Constant>(RemapOperand(CPS->getOperand(i), ValueMap)); - Result = ConstantStruct::get(cast<StructType>(CPS->getType()), Operands); - } else if (isa<ConstantPointerNull>(CPV) || isa<UndefValue>(CPV)) { - Result = const_cast<Constant*>(CPV); - } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CPV)) { - std::vector<Constant*> Operands(CP->getNumOperands()); - for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i) - Operands[i] = cast<Constant>(RemapOperand(CP->getOperand(i), ValueMap)); - Result = ConstantVector::get(Operands); - } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CPV)) { - std::vector<Constant*> Ops; - for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) - Ops.push_back(cast<Constant>(RemapOperand(CE->getOperand(i),ValueMap))); - Result = CE->getWithOperands(Ops); - } else if (isa<GlobalValue>(CPV)) { - assert(0 && "Unmapped global?"); - } else { - assert(0 && "Unknown type of derived type constant value!"); - } - } else if (isa<InlineAsm>(In)) { - Result = const_cast<Value*>(In); - } - - // Cache the mapping in our local map structure - if (Result) { - ValueMap[In] = Result; - return Result; - } - - - cerr << "LinkModules ValueMap: \n"; - PrintMap(ValueMap); - - cerr << "Couldn't remap value: " << (void*)In << " " << *In << "\n"; - assert(0 && "Couldn't remap value!"); - return 0; -} - -/// ForceRenaming - The LLVM SymbolTable class autorenames globals that conflict -/// in the symbol table. This is good for all clients except for us. Go -/// through the trouble to force this back. -static void ForceRenaming(GlobalValue *GV, const std::string &Name) { - assert(GV->getName() != Name && "Can't force rename to self"); - ValueSymbolTable &ST = GV->getParent()->getValueSymbolTable(); - - // If there is a conflict, rename the conflict. - if (GlobalValue *ConflictGV = cast_or_null<GlobalValue>(ST.lookup(Name))) { - assert(ConflictGV->hasInternalLinkage() && - "Not conflicting with a static global, should link instead!"); - GV->takeName(ConflictGV); - ConflictGV->setName(Name); // This will cause ConflictGV to get renamed - assert(ConflictGV->getName() != Name && "ForceRenaming didn't work"); - } else { - GV->setName(Name); // Force the name back - } -} - -/// CopyGVAttributes - copy additional attributes (those not needed to construct -/// a GlobalValue) from the SrcGV to the DestGV. -static void CopyGVAttributes(GlobalValue *DestGV, const GlobalValue *SrcGV) { - // Propagate alignment, visibility and section info. - DestGV->setAlignment(std::max(DestGV->getAlignment(), SrcGV->getAlignment())); - DestGV->setSection(SrcGV->getSection()); - DestGV->setVisibility(SrcGV->getVisibility()); - if (const Function *SrcF = dyn_cast<Function>(SrcGV)) { - Function *DestF = cast<Function>(DestGV); - DestF->setCallingConv(SrcF->getCallingConv()); - DestF->setParamAttrs(SrcF->getParamAttrs()); - if (SrcF->hasCollector()) - DestF->setCollector(SrcF->getCollector()); - } else if (const GlobalVariable *SrcVar = dyn_cast<GlobalVariable>(SrcGV)) { - GlobalVariable *DestVar = cast<GlobalVariable>(DestGV); - DestVar->setThreadLocal(SrcVar->isThreadLocal()); - } -} - -/// GetLinkageResult - This analyzes the two global values and determines what -/// the result will look like in the destination module. In particular, it -/// computes the resultant linkage type, computes whether the global in the -/// source should be copied over to the destination (replacing the existing -/// one), and computes whether this linkage is an error or not. It also performs -/// visibility checks: we cannot link together two symbols with different -/// visibilities. -static bool GetLinkageResult(GlobalValue *Dest, const GlobalValue *Src, - GlobalValue::LinkageTypes <, bool &LinkFromSrc, - std::string *Err) { - assert((!Dest || !Src->hasInternalLinkage()) && - "If Src has internal linkage, Dest shouldn't be set!"); - if (!Dest) { - // Linking something to nothing. - LinkFromSrc = true; - LT = Src->getLinkage(); - } else if (Src->isDeclaration()) { - // If Src is external or if both Src & Dest are external.. Just link the - // external globals, we aren't adding anything. - if (Src->hasDLLImportLinkage()) { - // If one of GVs has DLLImport linkage, result should be dllimport'ed. - if (Dest->isDeclaration()) { - LinkFromSrc = true; - LT = Src->getLinkage(); - } - } else if (Dest->hasExternalWeakLinkage()) { - //If the Dest is weak, use the source linkage - LinkFromSrc = true; - LT = Src->getLinkage(); - } else { - LinkFromSrc = false; - LT = Dest->getLinkage(); - } - } else if (Dest->isDeclaration() && !Dest->hasDLLImportLinkage()) { - // If Dest is external but Src is not: - LinkFromSrc = true; - LT = Src->getLinkage(); - } else if (Src->hasAppendingLinkage() || Dest->hasAppendingLinkage()) { - if (Src->getLinkage() != Dest->getLinkage()) - return Error(Err, "Linking globals named '" + Src->getName() + - "': can only link appending global with another appending global!"); - LinkFromSrc = true; // Special cased. - LT = Src->getLinkage(); - } else if (Src->hasWeakLinkage() || Src->hasLinkOnceLinkage()) { - // At this point we know that Dest has LinkOnce, External*, Weak, or - // DLL* linkage. - if ((Dest->hasLinkOnceLinkage() && Src->hasWeakLinkage()) || - Dest->hasExternalWeakLinkage()) { - LinkFromSrc = true; - LT = Src->getLinkage(); - } else { - LinkFromSrc = false; - LT = Dest->getLinkage(); - } - } else if (Dest->hasWeakLinkage() || Dest->hasLinkOnceLinkage()) { - // At this point we know that Src has External* or DLL* linkage. - if (Src->hasExternalWeakLinkage()) { - LinkFromSrc = false; - LT = Dest->getLinkage(); - } else { - LinkFromSrc = true; - LT = GlobalValue::ExternalLinkage; - } - } else { - assert((Dest->hasExternalLinkage() || - Dest->hasDLLImportLinkage() || - Dest->hasDLLExportLinkage() || - Dest->hasExternalWeakLinkage()) && - (Src->hasExternalLinkage() || - Src->hasDLLImportLinkage() || - Src->hasDLLExportLinkage() || - Src->hasExternalWeakLinkage()) && - "Unexpected linkage type!"); - return Error(Err, "Linking globals named '" + Src->getName() + - "': symbol multiply defined!"); - } - - // Check visibility - if (Dest && Src->getVisibility() != Dest->getVisibility()) - if (!Src->isDeclaration() && !Dest->isDeclaration()) - return Error(Err, "Linking globals named '" + Src->getName() + - "': symbols have different visibilities!"); - return false; -} - -// LinkGlobals - Loop through the global variables in the src module and merge -// them into the dest module. -static bool LinkGlobals(Module *Dest, const Module *Src, - std::map<const Value*, Value*> &ValueMap, - std::multimap<std::string, GlobalVariable *> &AppendingVars, - std::string *Err) { - // Loop over all of the globals in the src module, mapping them over as we go - for (Module::const_global_iterator I = Src->global_begin(), E = Src->global_end(); - I != E; ++I) { - const GlobalVariable *SGV = I; - GlobalValue *DGV = 0; - - // Check to see if may have to link the global with the global - if (SGV->hasName() && !SGV->hasInternalLinkage()) { - DGV = Dest->getGlobalVariable(SGV->getName()); - if (DGV && DGV->getType() != SGV->getType()) - // If types don't agree due to opaque types, try to resolve them. - RecursiveResolveTypes(SGV->getType(), DGV->getType(), - &Dest->getTypeSymbolTable(), ""); - } - - // Check to see if may have to link the global with the alias - if (!DGV && SGV->hasName() && !SGV->hasInternalLinkage()) { - DGV = Dest->getNamedAlias(SGV->getName()); - if (DGV && DGV->getType() != SGV->getType()) - // If types don't agree due to opaque types, try to resolve them. - RecursiveResolveTypes(SGV->getType(), DGV->getType(), - &Dest->getTypeSymbolTable(), ""); - } - - if (DGV && DGV->hasInternalLinkage()) - DGV = 0; - - assert((SGV->hasInitializer() || SGV->hasExternalWeakLinkage() || - SGV->hasExternalLinkage() || SGV->hasDLLImportLinkage()) && - "Global must either be external or have an initializer!"); - - GlobalValue::LinkageTypes NewLinkage = GlobalValue::InternalLinkage; - bool LinkFromSrc = false; - if (GetLinkageResult(DGV, SGV, NewLinkage, LinkFromSrc, Err)) - return true; - - if (!DGV) { - // No linking to be performed, simply create an identical version of the - // symbol over in the dest module... the initializer will be filled in - // later by LinkGlobalInits... - GlobalVariable *NewDGV = - new GlobalVariable(SGV->getType()->getElementType(), - SGV->isConstant(), SGV->getLinkage(), /*init*/0, - SGV->getName(), Dest); - // Propagate alignment, visibility and section info. - CopyGVAttributes(NewDGV, SGV); - - // If the LLVM runtime renamed the global, but it is an externally visible - // symbol, DGV must be an existing global with internal linkage. Rename - // it. - if (NewDGV->getName() != SGV->getName() && !NewDGV->hasInternalLinkage()) - ForceRenaming(NewDGV, SGV->getName()); - - // Make sure to remember this mapping... - ValueMap[SGV] = NewDGV; - - if (SGV->hasAppendingLinkage()) - // Keep track that this is an appending variable... - AppendingVars.insert(std::make_pair(SGV->getName(), NewDGV)); - } else if (DGV->hasAppendingLinkage()) { - // No linking is performed yet. Just insert a new copy of the global, and - // keep track of the fact that it is an appending variable in the - // AppendingVars map. The name is cleared out so that no linkage is - // performed. - GlobalVariable *NewDGV = - new GlobalVariable(SGV->getType()->getElementType(), - SGV->isConstant(), SGV->getLinkage(), /*init*/0, - "", Dest); - - // Set alignment allowing CopyGVAttributes merge it with alignment of SGV. - NewDGV->setAlignment(DGV->getAlignment()); - // Propagate alignment, section and visibility info. - CopyGVAttributes(NewDGV, SGV); - - // Make sure to remember this mapping... - ValueMap[SGV] = NewDGV; - - // Keep track that this is an appending variable... - AppendingVars.insert(std::make_pair(SGV->getName(), NewDGV)); - } else if (GlobalAlias *DGA = dyn_cast<GlobalAlias>(DGV)) { - // SGV is global, but DGV is alias. The only valid mapping is when SGV is - // external declaration, which is effectively a no-op. Also make sure - // linkage calculation was correct. - if (SGV->isDeclaration() && !LinkFromSrc) { - // Make sure to remember this mapping... - ValueMap[SGV] = DGA; - } else - return Error(Err, "Global-Alias Collision on '" + SGV->getName() + - "': symbol multiple defined"); - } else if (GlobalVariable *DGVar = dyn_cast<GlobalVariable>(DGV)) { - // Otherwise, perform the global-global mapping as instructed by - // GetLinkageResult. - if (LinkFromSrc) { - // Propagate alignment, section, and visibility info. - CopyGVAttributes(DGVar, SGV); - - // If the types don't match, and if we are to link from the source, nuke - // DGV and create a new one of the appropriate type. - if (SGV->getType() != DGVar->getType()) { - GlobalVariable *NewDGV = - new GlobalVariable(SGV->getType()->getElementType(), - DGVar->isConstant(), DGVar->getLinkage(), - /*init*/0, DGVar->getName(), Dest); - CopyGVAttributes(NewDGV, DGVar); - DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewDGV, - DGVar->getType())); - // DGVar will conflict with NewDGV because they both had the same - // name. We must erase this now so ForceRenaming doesn't assert - // because DGV might not have internal linkage. - DGVar->eraseFromParent(); - - // If the symbol table renamed the global, but it is an externally - // visible symbol, DGV must be an existing global with internal - // linkage. Rename it. - if (NewDGV->getName() != SGV->getName() && - !NewDGV->hasInternalLinkage()) - ForceRenaming(NewDGV, SGV->getName()); - - DGVar = NewDGV; - } - - // Inherit const as appropriate - DGVar->setConstant(SGV->isConstant()); - - // Set initializer to zero, so we can link the stuff later - DGVar->setInitializer(0); - } else { - // Special case for const propagation - if (DGVar->isDeclaration() && SGV->isConstant() && !DGVar->isConstant()) - DGVar->setConstant(true); - } - - // Set calculated linkage - DGVar->setLinkage(NewLinkage); - - // Make sure to remember this mapping... - ValueMap[SGV] = ConstantExpr::getBitCast(DGVar, SGV->getType()); - } - } - return false; -} - -static GlobalValue::LinkageTypes -CalculateAliasLinkage(const GlobalValue *SGV, const GlobalValue *DGV) { - if (SGV->hasExternalLinkage() || DGV->hasExternalLinkage()) - return GlobalValue::ExternalLinkage; - else if (SGV->hasWeakLinkage() || DGV->hasWeakLinkage()) - return GlobalValue::WeakLinkage; - else { - assert(SGV->hasInternalLinkage() && DGV->hasInternalLinkage() && - "Unexpected linkage type"); - return GlobalValue::InternalLinkage; - } -} - -// LinkAlias - Loop through the alias in the src module and link them into the -// dest module. We're assuming, that all functions/global variables were already -// linked in. -static bool LinkAlias(Module *Dest, const Module *Src, - std::map<const Value*, Value*> &ValueMap, - std::string *Err) { - // Loop over all alias in the src module - for (Module::const_alias_iterator I = Src->alias_begin(), - E = Src->alias_end(); I != E; ++I) { - const GlobalAlias *SGA = I; - const GlobalValue *SAliasee = SGA->getAliasedGlobal(); - GlobalAlias *NewGA = NULL; - - // Globals were already linked, thus we can just query ValueMap for variant - // of SAliasee in Dest - std::map<const Value*,Value*>::const_iterator VMI = ValueMap.find(SAliasee); - assert(VMI != ValueMap.end() && "Aliasee not linked"); - GlobalValue* DAliasee = cast<GlobalValue>(VMI->second); - - // Try to find something 'similar' to SGA in destination module. - if (GlobalAlias *DGA = Dest->getNamedAlias(SGA->getName())) { - // If types don't agree due to opaque types, try to resolve them. - if (RecursiveResolveTypes(SGA->getType(), DGA->getType(), - &Dest->getTypeSymbolTable(), "")) - return Error(Err, "Alias Collision on '" + SGA->getName()+ - "': aliases have different types"); - - // Now types are known to be the same, check whether aliasees equal. As - // globals are already linked we just need query ValueMap to find the - // mapping. - if (DAliasee == DGA->getAliasedGlobal()) { - // This is just two copies of the same alias. Propagate linkage, if - // necessary. - DGA->setLinkage(CalculateAliasLinkage(SGA, DGA)); - - NewGA = DGA; - // Proceed to 'common' steps - } else - return Error(Err, "Alias Collision on '" + SGA->getName()+ - "': aliases have different aliasees"); - } else if (GlobalVariable *DGV = Dest->getGlobalVariable(SGA->getName())) { - RecursiveResolveTypes(SGA->getType(), DGV->getType(), - &Dest->getTypeSymbolTable(), ""); - - // The only allowed way is to link alias with external declaration. - if (DGV->isDeclaration()) { - // But only if aliasee is global too... - if (!isa<GlobalVariable>(DAliasee)) - return Error(Err, "Global-Alias Collision on '" + SGA->getName() + - "': aliasee is not global variable"); - - NewGA = new GlobalAlias(SGA->getType(), SGA->getLinkage(), - SGA->getName(), DAliasee, Dest); - CopyGVAttributes(NewGA, SGA); - - // Any uses of DGV need to change to NewGA, with cast, if needed. - if (SGA->getType() != DGV->getType()) - DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewGA, - DGV->getType())); - else - DGV->replaceAllUsesWith(NewGA); - - // DGV will conflict with NewGA because they both had the same - // name. We must erase this now so ForceRenaming doesn't assert - // because DGV might not have internal linkage. - DGV->eraseFromParent(); - - // Proceed to 'common' steps - } else - return Error(Err, "Global-Alias Collision on '" + SGA->getName() + - "': symbol multiple defined"); - } else if (Function *DF = Dest->getFunction(SGA->getName())) { - RecursiveResolveTypes(SGA->getType(), DF->getType(), - &Dest->getTypeSymbolTable(), ""); - - // The only allowed way is to link alias with external declaration. - if (DF->isDeclaration()) { - // But only if aliasee is function too... - if (!isa<Function>(DAliasee)) - return Error(Err, "Function-Alias Collision on '" + SGA->getName() + - "': aliasee is not function"); - - NewGA = new GlobalAlias(SGA->getType(), SGA->getLinkage(), - SGA->getName(), DAliasee, Dest); - CopyGVAttributes(NewGA, SGA); - - // Any uses of DF need to change to NewGA, with cast, if needed. - if (SGA->getType() != DF->getType()) - DF->replaceAllUsesWith(ConstantExpr::getBitCast(NewGA, - DF->getType())); - else - DF->replaceAllUsesWith(NewGA); - - // DF will conflict with NewGA because they both had the same - // name. We must erase this now so ForceRenaming doesn't assert - // because DF might not have internal linkage. - DF->eraseFromParent(); - - // Proceed to 'common' steps - } else - return Error(Err, "Function-Alias Collision on '" + SGA->getName() + - "': symbol multiple defined"); - } else { - // Nothing similar found, just copy alias into destination module. - - NewGA = new GlobalAlias(SGA->getType(), SGA->getLinkage(), - SGA->getName(), DAliasee, Dest); - CopyGVAttributes(NewGA, SGA); - - // Proceed to 'common' steps - } - - assert(NewGA && "No alias was created in destination module!"); - - // If the symbol table renamed the alias, but it is an externally visible - // symbol, DGV must be an global value with internal linkage. Rename it. - if (NewGA->getName() != SGA->getName() && - !NewGA->hasInternalLinkage()) - ForceRenaming(NewGA, SGA->getName()); - - // Remember this mapping so uses in the source module get remapped - // later by RemapOperand. - ValueMap[SGA] = NewGA; - } - - return false; -} - - -// LinkGlobalInits - Update the initializers in the Dest module now that all -// globals that may be referenced are in Dest. -static bool LinkGlobalInits(Module *Dest, const Module *Src, - std::map<const Value*, Value*> &ValueMap, - std::string *Err) { - - // Loop over all of the globals in the src module, mapping them over as we go - for (Module::const_global_iterator I = Src->global_begin(), - E = Src->global_end(); I != E; ++I) { - const GlobalVariable *SGV = I; - - if (SGV->hasInitializer()) { // Only process initialized GV's - // Figure out what the initializer looks like in the dest module... - Constant *SInit = - cast<Constant>(RemapOperand(SGV->getInitializer(), ValueMap)); - - GlobalVariable *DGV = - cast<GlobalVariable>(ValueMap[SGV]->stripPointerCasts()); - if (DGV->hasInitializer()) { - if (SGV->hasExternalLinkage()) { - if (DGV->getInitializer() != SInit) - return Error(Err, "Global Variable Collision on '" + SGV->getName() + - "': global variables have different initializers"); - } else if (DGV->hasLinkOnceLinkage() || DGV->hasWeakLinkage()) { - // Nothing is required, mapped values will take the new global - // automatically. - } else if (SGV->hasLinkOnceLinkage() || SGV->hasWeakLinkage()) { - // Nothing is required, mapped values will take the new global - // automatically. - } else if (DGV->hasAppendingLinkage()) { - assert(0 && "Appending linkage unimplemented!"); - } else { - assert(0 && "Unknown linkage!"); - } - } else { - // Copy the initializer over now... - DGV->setInitializer(SInit); - } - } - } - return false; -} - -// LinkFunctionProtos - Link the functions together between the two modules, -// without doing function bodies... this just adds external function prototypes -// to the Dest function... -// -static bool LinkFunctionProtos(Module *Dest, const Module *Src, - std::map<const Value*, Value*> &ValueMap, - std::string *Err) { - // Loop over all of the functions in the src module, mapping them over - for (Module::const_iterator I = Src->begin(), E = Src->end(); I != E; ++I) { - const Function *SF = I; // SrcFunction - Function *DF = 0; - if (SF->hasName() && !SF->hasInternalLinkage()) { - // Check to see if may have to link the function. - DF = Dest->getFunction(SF->getName()); - if (DF && SF->getType() != DF->getType()) - // If types don't agree because of opaque, try to resolve them - RecursiveResolveTypes(SF->getType(), DF->getType(), - &Dest->getTypeSymbolTable(), ""); - } - - // Check visibility - if (DF && !DF->hasInternalLinkage() && - SF->getVisibility() != DF->getVisibility()) { - // If one is a prototype, ignore its visibility. Prototypes are always - // overridden by the definition. - if (!SF->isDeclaration() && !DF->isDeclaration()) - return Error(Err, "Linking functions named '" + SF->getName() + - "': symbols have different visibilities!"); - } - - if (DF && DF->hasInternalLinkage()) - DF = NULL; - - if (DF && DF->getType() != SF->getType()) { - if (DF->isDeclaration() && !SF->isDeclaration()) { - // We have a definition of the same name but different type in the - // source module. Copy the prototype to the destination and replace - // uses of the destination's prototype with the new prototype. - Function *NewDF = Function::Create(SF->getFunctionType(), SF->getLinkage(), - SF->getName(), Dest); - CopyGVAttributes(NewDF, SF); - - // Any uses of DF need to change to NewDF, with cast - DF->replaceAllUsesWith(ConstantExpr::getBitCast(NewDF, DF->getType())); - - // DF will conflict with NewDF because they both had the same. We must - // erase this now so ForceRenaming doesn't assert because DF might - // not have internal linkage. - DF->eraseFromParent(); - - // If the symbol table renamed the function, but it is an externally - // visible symbol, DF must be an existing function with internal - // linkage. Rename it. - if (NewDF->getName() != SF->getName() && !NewDF->hasInternalLinkage()) - ForceRenaming(NewDF, SF->getName()); - - // Remember this mapping so uses in the source module get remapped - // later by RemapOperand. - ValueMap[SF] = NewDF; - } else if (SF->isDeclaration()) { - // We have two functions of the same name but different type and the - // source is a declaration while the destination is not. Any use of - // the source must be mapped to the destination, with a cast. - ValueMap[SF] = ConstantExpr::getBitCast(DF, SF->getType()); - } else { - // We have two functions of the same name but different types and they - // are both definitions. This is an error. - return Error(Err, "Function '" + DF->getName() + "' defined as both '" + - ToStr(SF->getFunctionType(), Src) + "' and '" + - ToStr(DF->getFunctionType(), Dest) + "'"); - } - } else if (!DF || SF->hasInternalLinkage() || DF->hasInternalLinkage()) { - // Function does not already exist, simply insert an function signature - // identical to SF into the dest module. - Function *NewDF = Function::Create(SF->getFunctionType(), SF->getLinkage(), - SF->getName(), Dest); - CopyGVAttributes(NewDF, SF); - - // If the LLVM runtime renamed the function, but it is an externally - // visible symbol, DF must be an existing function with internal linkage. - // Rename it. - if (NewDF->getName() != SF->getName() && !NewDF->hasInternalLinkage()) - ForceRenaming(NewDF, SF->getName()); - - // ... and remember this mapping... - ValueMap[SF] = NewDF; - } else if (SF->isDeclaration()) { - // If SF is a declaration or if both SF & DF are declarations, just link - // the declarations, we aren't adding anything. - if (SF->hasDLLImportLinkage()) { - if (DF->isDeclaration()) { - ValueMap.insert(std::make_pair(SF, DF)); - DF->setLinkage(SF->getLinkage()); - } - } else { - ValueMap[SF] = DF; - } - } else if (DF->isDeclaration() && !DF->hasDLLImportLinkage()) { - // If DF is external but SF is not... - // Link the external functions, update linkage qualifiers - ValueMap.insert(std::make_pair(SF, DF)); - DF->setLinkage(SF->getLinkage()); - // Visibility of prototype is overridden by vis of definition. - DF->setVisibility(SF->getVisibility()); - } else if (SF->hasWeakLinkage() || SF->hasLinkOnceLinkage()) { - // At this point we know that DF has LinkOnce, Weak, or External* linkage. - ValueMap[SF] = DF; - - // Linkonce+Weak = Weak - // *+External Weak = * - if ((DF->hasLinkOnceLinkage() && SF->hasWeakLinkage()) || - DF->hasExternalWeakLinkage()) - DF->setLinkage(SF->getLinkage()); - } else if (DF->hasWeakLinkage() || DF->hasLinkOnceLinkage()) { - // At this point we know that SF has LinkOnce or External* linkage. - ValueMap[SF] = DF; - if (!SF->hasLinkOnceLinkage() && !SF->hasExternalWeakLinkage()) - // Don't inherit linkonce & external weak linkage - DF->setLinkage(SF->getLinkage()); - } else if (SF->getLinkage() != DF->getLinkage()) { - return Error(Err, "Functions named '" + SF->getName() + - "' have different linkage specifiers!"); - } else if (SF->hasExternalLinkage()) { - // The function is defined identically in both modules!! - return Error(Err, "Function '" + - ToStr(SF->getFunctionType(), Src) + "':\"" + - SF->getName() + "\" - Function is already defined!"); - } else { - assert(0 && "Unknown linkage configuration found!"); - } - } - return false; -} - -// LinkFunctionBody - Copy the source function over into the dest function and -// fix up references to values. At this point we know that Dest is an external -// function, and that Src is not. -static bool LinkFunctionBody(Function *Dest, Function *Src, - std::map<const Value*, Value*> &ValueMap, - std::string *Err) { - assert(Src && Dest && Dest->isDeclaration() && !Src->isDeclaration()); - - // Go through and convert function arguments over, remembering the mapping. - Function::arg_iterator DI = Dest->arg_begin(); - for (Function::arg_iterator I = Src->arg_begin(), E = Src->arg_end(); - I != E; ++I, ++DI) { - DI->setName(I->getName()); // Copy the name information over... - - // Add a mapping to our local map - ValueMap[I] = DI; - } - - // Splice the body of the source function into the dest function. - Dest->getBasicBlockList().splice(Dest->end(), Src->getBasicBlockList()); - - // At this point, all of the instructions and values of the function are now - // copied over. The only problem is that they are still referencing values in - // the Source function as operands. Loop through all of the operands of the - // functions and patch them up to point to the local versions... - // - for (Function::iterator BB = Dest->begin(), BE = Dest->end(); BB != BE; ++BB) - for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) - for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end(); - OI != OE; ++OI) - if (!isa<Instruction>(*OI) && !isa<BasicBlock>(*OI)) - *OI = RemapOperand(*OI, ValueMap); - - // There is no need to map the arguments anymore. - for (Function::arg_iterator I = Src->arg_begin(), E = Src->arg_end(); - I != E; ++I) - ValueMap.erase(I); - - return false; -} - - -// LinkFunctionBodies - Link in the function bodies that are defined in the -// source module into the DestModule. This consists basically of copying the -// function over and fixing up references to values. -static bool LinkFunctionBodies(Module *Dest, Module *Src, - std::map<const Value*, Value*> &ValueMap, - std::string *Err) { - - // Loop over all of the functions in the src module, mapping them over as we - // go - for (Module::iterator SF = Src->begin(), E = Src->end(); SF != E; ++SF) { - if (!SF->isDeclaration()) { // No body if function is external - Function *DF = cast<Function>(ValueMap[SF]); // Destination function - - // DF not external SF external? - if (DF->isDeclaration()) - // Only provide the function body if there isn't one already. - if (LinkFunctionBody(DF, SF, ValueMap, Err)) - return true; - } - } - return false; -} - -// LinkAppendingVars - If there were any appending global variables, link them -// together now. Return true on error. -static bool LinkAppendingVars(Module *M, - std::multimap<std::string, GlobalVariable *> &AppendingVars, - std::string *ErrorMsg) { - if (AppendingVars.empty()) return false; // Nothing to do. - - // Loop over the multimap of appending vars, processing any variables with the - // same name, forming a new appending global variable with both of the - // initializers merged together, then rewrite references to the old variables - // and delete them. - std::vector<Constant*> Inits; - while (AppendingVars.size() > 1) { - // Get the first two elements in the map... - std::multimap<std::string, - GlobalVariable*>::iterator Second = AppendingVars.begin(), First=Second++; - - // If the first two elements are for different names, there is no pair... - // Otherwise there is a pair, so link them together... - if (First->first == Second->first) { - GlobalVariable *G1 = First->second, *G2 = Second->second; - const ArrayType *T1 = cast<ArrayType>(G1->getType()->getElementType()); - const ArrayType *T2 = cast<ArrayType>(G2->getType()->getElementType()); - - // Check to see that they two arrays agree on type... - if (T1->getElementType() != T2->getElementType()) - return Error(ErrorMsg, - "Appending variables with different element types need to be linked!"); - if (G1->isConstant() != G2->isConstant()) - return Error(ErrorMsg, - "Appending variables linked with different const'ness!"); - - if (G1->getAlignment() != G2->getAlignment()) - return Error(ErrorMsg, - "Appending variables with different alignment need to be linked!"); - - if (G1->getVisibility() != G2->getVisibility()) - return Error(ErrorMsg, - "Appending variables with different visibility need to be linked!"); - - if (G1->getSection() != G2->getSection()) - return Error(ErrorMsg, - "Appending variables with different section name need to be linked!"); - - unsigned NewSize = T1->getNumElements() + T2->getNumElements(); - ArrayType *NewType = ArrayType::get(T1->getElementType(), NewSize); - - G1->setName(""); // Clear G1's name in case of a conflict! - - // Create the new global variable... - GlobalVariable *NG = - new GlobalVariable(NewType, G1->isConstant(), G1->getLinkage(), - /*init*/0, First->first, M, G1->isThreadLocal()); - - // Propagate alignment, visibility and section info. - CopyGVAttributes(NG, G1); - - // Merge the initializer... - Inits.reserve(NewSize); - if (ConstantArray *I = dyn_cast<ConstantArray>(G1->getInitializer())) { - for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i) - Inits.push_back(I->getOperand(i)); - } else { - assert(isa<ConstantAggregateZero>(G1->getInitializer())); - Constant *CV = Constant::getNullValue(T1->getElementType()); - for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i) - Inits.push_back(CV); - } - if (ConstantArray *I = dyn_cast<ConstantArray>(G2->getInitializer())) { - for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i) - Inits.push_back(I->getOperand(i)); - } else { - assert(isa<ConstantAggregateZero>(G2->getInitializer())); - Constant *CV = Constant::getNullValue(T2->getElementType()); - for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i) - Inits.push_back(CV); - } - NG->setInitializer(ConstantArray::get(NewType, Inits)); - Inits.clear(); - - // Replace any uses of the two global variables with uses of the new - // global... - - // FIXME: This should rewrite simple/straight-forward uses such as - // getelementptr instructions to not use the Cast! - G1->replaceAllUsesWith(ConstantExpr::getBitCast(NG, G1->getType())); - G2->replaceAllUsesWith(ConstantExpr::getBitCast(NG, G2->getType())); - - // Remove the two globals from the module now... - M->getGlobalList().erase(G1); - M->getGlobalList().erase(G2); - - // Put the new global into the AppendingVars map so that we can handle - // linking of more than two vars... - Second->second = NG; - } - AppendingVars.erase(First); - } - - return false; -} - -static bool ResolveAliases(Module *Dest) { - for (Module::alias_iterator I = Dest->alias_begin(), E = Dest->alias_end(); - I != E; ++I) - if (const GlobalValue *GV = I->resolveAliasedGlobal()) - if (!GV->isDeclaration()) - I->replaceAllUsesWith(const_cast<GlobalValue*>(GV)); - - return false; -} - -// LinkModules - This function links two modules together, with the resulting -// left module modified to be the composite of the two input modules. If an -// error occurs, true is returned and ErrorMsg (if not null) is set to indicate -// the problem. Upon failure, the Dest module could be in a modified state, and -// shouldn't be relied on to be consistent. -bool -Linker::LinkModules(Module *Dest, Module *Src, std::string *ErrorMsg) { - assert(Dest != 0 && "Invalid Destination module"); - assert(Src != 0 && "Invalid Source Module"); - - if (Dest->getDataLayout().empty()) { - if (!Src->getDataLayout().empty()) { - Dest->setDataLayout(Src->getDataLayout()); - } else { - std::string DataLayout; - - if (Dest->getEndianness() == Module::AnyEndianness) { - if (Src->getEndianness() == Module::BigEndian) - DataLayout.append("E"); - else if (Src->getEndianness() == Module::LittleEndian) - DataLayout.append("e"); - } - - if (Dest->getPointerSize() == Module::AnyPointerSize) { - if (Src->getPointerSize() == Module::Pointer64) - DataLayout.append(DataLayout.length() == 0 ? "p:64:64" : "-p:64:64"); - else if (Src->getPointerSize() == Module::Pointer32) - DataLayout.append(DataLayout.length() == 0 ? "p:32:32" : "-p:32:32"); - } - Dest->setDataLayout(DataLayout); - } - } - - // Copy the target triple from the source to dest if the dest's is empty. - if (Dest->getTargetTriple().empty() && !Src->getTargetTriple().empty()) - Dest->setTargetTriple(Src->getTargetTriple()); - - if (!Src->getDataLayout().empty() && !Dest->getDataLayout().empty() && - Src->getDataLayout() != Dest->getDataLayout()) - cerr << "WARNING: Linking two modules of different data layouts!\n"; - if (!Src->getTargetTriple().empty() && - Dest->getTargetTriple() != Src->getTargetTriple()) - cerr << "WARNING: Linking two modules of different target triples!\n"; - - // Append the module inline asm string. - if (!Src->getModuleInlineAsm().empty()) { - if (Dest->getModuleInlineAsm().empty()) - Dest->setModuleInlineAsm(Src->getModuleInlineAsm()); - else - Dest->setModuleInlineAsm(Dest->getModuleInlineAsm()+"\n"+ - Src->getModuleInlineAsm()); - } - - // Update the destination module's dependent libraries list with the libraries - // from the source module. There's no opportunity for duplicates here as the - // Module ensures that duplicate insertions are discarded. - for (Module::lib_iterator SI = Src->lib_begin(), SE = Src->lib_end(); - SI != SE; ++SI) - Dest->addLibrary(*SI); - - // LinkTypes - Go through the symbol table of the Src module and see if any - // types are named in the src module that are not named in the Dst module. - // Make sure there are no type name conflicts. - if (LinkTypes(Dest, Src, ErrorMsg)) - return true; - - // ValueMap - Mapping of values from what they used to be in Src, to what they - // are now in Dest. - std::map<const Value*, Value*> ValueMap; - - // AppendingVars - Keep track of global variables in the destination module - // with appending linkage. After the module is linked together, they are - // appended and the module is rewritten. - std::multimap<std::string, GlobalVariable *> AppendingVars; - for (Module::global_iterator I = Dest->global_begin(), E = Dest->global_end(); - I != E; ++I) { - // Add all of the appending globals already in the Dest module to - // AppendingVars. - if (I->hasAppendingLinkage()) - AppendingVars.insert(std::make_pair(I->getName(), I)); - } - - // Insert all of the globals in src into the Dest module... without linking - // initializers (which could refer to functions not yet mapped over). - if (LinkGlobals(Dest, Src, ValueMap, AppendingVars, ErrorMsg)) - return true; - - // Link the functions together between the two modules, without doing function - // bodies... this just adds external function prototypes to the Dest - // function... We do this so that when we begin processing function bodies, - // all of the global values that may be referenced are available in our - // ValueMap. - if (LinkFunctionProtos(Dest, Src, ValueMap, ErrorMsg)) - return true; - - // If there were any alias, link them now. We really need to do this now, - // because all of the aliases that may be referenced need to be available in - // ValueMap - if (LinkAlias(Dest, Src, ValueMap, ErrorMsg)) return true; - - // Update the initializers in the Dest module now that all globals that may - // be referenced are in Dest. - if (LinkGlobalInits(Dest, Src, ValueMap, ErrorMsg)) return true; - - // Link in the function bodies that are defined in the source module into the - // DestModule. This consists basically of copying the function over and - // fixing up references to values. - if (LinkFunctionBodies(Dest, Src, ValueMap, ErrorMsg)) return true; - - // If there were any appending global variables, link them together now. - if (LinkAppendingVars(Dest, AppendingVars, ErrorMsg)) return true; - - // Resolve all uses of aliases with aliasees - if (ResolveAliases(Dest)) return true; - - // If the source library's module id is in the dependent library list of the - // destination library, remove it since that module is now linked in. - sys::Path modId; - modId.set(Src->getModuleIdentifier()); - if (!modId.isEmpty()) - Dest->removeLibrary(modId.getBasename()); - - return false; -} - -// vim: sw=2 |