C++ GlobalAlias类代码示例

static void initOverload(OverloadPtr x) {
    EnvPtr env = overloadPatternEnv(x);
    PatternPtr pattern = evaluateOnePattern(x->target, env);
    ObjectPtr obj = derefDeep(pattern);
    if (obj == NULL) {
        x->nameIsPattern = true;
        addPatternOverload(x);
    }
    else {
        switch (obj->objKind) {
        case PROCEDURE : {
            Procedure *proc = (Procedure *)obj.ptr();
            addProcedureOverload(proc, env, x);
            break;
        }
        case RECORD_DECL : {
            RecordDecl *r = (RecordDecl *)obj.ptr();
            r->overloads.insert(r->overloads.begin(), x);
            break;
        }
        case VARIANT_DECL : {
            VariantDecl *v = (VariantDecl *)obj.ptr();
            v->overloads.insert(v->overloads.begin(), x);
            break;
        }
        case TYPE : {
            Type *t = (Type *)obj.ptr();
            t->overloads.insert(t->overloads.begin(), x);
            break;
        }
        case PRIM_OP : {
            if (isOverloadablePrimOp(obj))
                addPrimOpOverload((PrimOp *)obj.ptr(), x);
            else
                error(x->target, "invalid overload target");
            break;
        }
        case GLOBAL_ALIAS : {
            GlobalAlias *a = (GlobalAlias*)obj.ptr();
            if (!a->hasParams())
                error(x->target, "invalid overload target");
            a->overloads.insert(a->overloads.begin(), x);
            break;
        }
        case INTRINSIC : {
            error(x->target, "invalid overload target");
        }
        default : {
            error(x->target, "invalid overload target");
        }
        }
    }
}

static void AliasGToF(Function *F, Function *G) {
  if (!G->hasExternalLinkage() && !G->hasLocalLinkage() && !G->hasWeakLinkage())
    return ThunkGToF(F, G);

  GlobalAlias *GA = new GlobalAlias(
    G->getType(), G->getLinkage(), "",
    ConstantExpr::getBitCast(F, G->getType()), G->getParent());
  F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
  GA->takeName(G);
  GA->setVisibility(G->getVisibility());
  G->replaceAllUsesWith(GA);
  G->eraseFromParent();
}

Module * llvmutil_extractmodule(Module * OrigMod, TargetMachine * TM, std::vector<Function*> * livefns, std::vector<std::string> * symbolnames) {
        assert(symbolnames == NULL || livefns->size() == symbolnames->size());
        ValueToValueMapTy VMap;
        Module * M = CloneModule(OrigMod, VMap);
        PassManager * MPM = new PassManager();
        
        llvmutil_addtargetspecificpasses(MPM, TM);
        
        std::vector<const char *> names;
        for(size_t i = 0; i < livefns->size(); i++) {
            Function * fn = cast<Function>(VMap[(*livefns)[i]]);
            const char * name;
            if(symbolnames) {
                GlobalAlias * ga = new GlobalAlias(fn->getType(), Function::ExternalLinkage, (*symbolnames)[i], fn, M);
                name = copyName(ga->getName());
            } else {
                name = copyName(fn->getName());
            }
            names.push_back(name); //internalize pass has weird interface, so we need to copy the names here
        }
        
        //at this point we run optimizations on the module
        //first internalize all functions not mentioned in "names" using an internalize pass and then perform 
        //standard optimizations
        
        MPM->add(createVerifierPass()); //make sure we haven't messed stuff up yet
        MPM->add(createInternalizePass(names));
        MPM->add(createGlobalDCEPass()); //run this early since anything not in the table of exported functions is still in this module
                                         //this will remove dead functions
        
        //clean up the name list
        for(size_t i = 0; i < names.size(); i++) {
            free((char*)names[i]);
            names[i] = NULL;
        }
        
        PassManagerBuilder PMB;
        PMB.OptLevel = 3;
        PMB.DisableUnrollLoops = true;
        
        PMB.populateModulePassManager(*MPM);
        //PMB.populateLTOPassManager(*MPM, false, false); //no need to re-internalize, we already did it
    
        MPM->run(*M);
        
        delete MPM;
        MPM = NULL;
    
        return M;
}

// Replace G with an alias to F and delete G.
void MergeFunctions::writeAlias(Function *F, Function *G) {
  Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
  GlobalAlias *GA = new GlobalAlias(G->getType(), G->getLinkage(), "",
                                    BitcastF, G->getParent());
  F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
  GA->takeName(G);
  GA->setVisibility(G->getVisibility());
  removeUsers(G);
  G->replaceAllUsesWith(GA);
  G->eraseFromParent();

  DEBUG(dbgs() << "writeAlias: " << GA->getName() << '\n');
  ++NumAliasesWritten;
}

static void
computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
                    DenseSet<GlobalValue::GUID> &CantBePromoted) {
  bool NonRenamableLocal = isNonRenamableLocal(A);
  GlobalValueSummary::GVFlags Flags(A.getLinkage(), NonRenamableLocal,
                                    /* LiveRoot = */ false);
  auto AS = llvm::make_unique<AliasSummary>(Flags, ArrayRef<ValueInfo>{});
  auto *Aliasee = A.getBaseObject();
  auto *AliaseeSummary = Index.getGlobalValueSummary(*Aliasee);
  assert(AliaseeSummary && "Alias expects aliasee summary to be parsed");
  AS->setAliasee(AliaseeSummary);
  if (NonRenamableLocal)
    CantBePromoted.insert(A.getGUID());
  Index.addGlobalValueSummary(A.getName(), std::move(AS));
}

 static Function*
 resolveFunction(Module& M, StringRef name)
 {
   Function* f = M.getFunction(name);
   if (f != NULL)
     return f;
   GlobalAlias* ga = M.getNamedAlias(name);
   if (ga != NULL) {
     const GlobalValue* v = ga->resolveAliasedGlobal(true);
     f = dyn_cast<Function>(const_cast<GlobalValue*>(v));
     if (f != NULL) {
       errs() << "Resolved alias " << name << " to " << f->getName() << "\n";
       return f;
     }
   }
   return NULL;
 }

/// LinkAliasProto - Set up prototypes for any aliases that come over from the
/// source module.
bool ModuleLinker::linkAliasProto(GlobalAlias *SGA) {
  GlobalValue *DGV = getLinkedToGlobal(SGA);
  llvm::Optional<GlobalValue::VisibilityTypes> NewVisibility;

  if (DGV) {
    GlobalValue::LinkageTypes NewLinkage = GlobalValue::InternalLinkage;
    GlobalValue::VisibilityTypes NV;
    bool LinkFromSrc = false;
    if (getLinkageResult(DGV, SGA, NewLinkage, NV, LinkFromSrc))
      return true;
    NewVisibility = NV;

    if (!LinkFromSrc) {
      // Set calculated linkage.
      DGV->setLinkage(NewLinkage);
      DGV->setVisibility(*NewVisibility);

      // Make sure to remember this mapping.
      ValueMap[SGA] = ConstantExpr::getBitCast(DGV,TypeMap.get(SGA->getType()));
      
      // Track the alias from the source module so we don't attempt to remap it.
      DoNotLinkFromSource.insert(SGA);
      
      return false;
    }
  }
  
  // If there is no linkage to be performed or we're linking from the source,
  // bring over SGA.
  GlobalAlias *NewDA = new GlobalAlias(TypeMap.get(SGA->getType()),
                                       SGA->getLinkage(), SGA->getName(),
                                       /*aliasee*/0, DstM);
  CopyGVAttributes(NewDA, SGA);
  if (NewVisibility)
    NewDA->setVisibility(*NewVisibility);

  if (DGV) {
    // Any uses of DGV need to change to NewDA, with cast.
    DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewDA, DGV->getType()));
    DGV->eraseFromParent();
  }
  
  ValueMap[SGA] = NewDA;
  return false;
}

//
// Method: runOnModule()
//
// Description:
//  Entry point for this LLVM pass.
//  Replace all internal aliases with the
//  aliasee value
//
// Inputs:
//  M - A reference to the LLVM module to transform
//
// Outputs:
//  M - The transformed LLVM module.
//
// Return value:
//  true  - The module was modified.
//  false - The module was not modified.
//
bool FuncSimplify::runOnModule(Module& M) {

  std::vector<GlobalAlias*> toDelete;
  for (Module::alias_iterator I = M.alias_begin(); I != M.alias_end(); ++I) {
    if(!I->hasInternalLinkage())
      continue;
    I->replaceAllUsesWith(I->getAliasee());
    toDelete.push_back(I);
  }
  numChanged += toDelete.size();

  while(!toDelete.empty()) {
    GlobalAlias *I = toDelete.back();
    toDelete.pop_back();
    I->eraseFromParent();
  }


  return true;
}

static llvm::ArrayRef<OverloadPtr> callableOverloads(ObjectPtr x)
{
    initCallable(x);
    switch (x->objKind) {
    case TYPE : {
        Type *y = (Type *)x.ptr();
        return y->overloads;
    }
    case RECORD_DECL : {
        RecordDecl *y = (RecordDecl *)x.ptr();
        return y->overloads;
    }
    case VARIANT_DECL : {
        VariantDecl *y = (VariantDecl *)x.ptr();
        return y->overloads;
    }
    case PROCEDURE : {
        Procedure *y = (Procedure *)x.ptr();
        return y->overloads;
    }
    case PRIM_OP : {
        assert(isOverloadablePrimOp(x));
        PrimOp *y = (PrimOp *)x.ptr();
        return primOpOverloads(y);
    }
    case GLOBAL_ALIAS : {
        GlobalAlias *a = (GlobalAlias *)x.ptr();
        assert(a->hasParams());
        return a->overloads;
    }
    default : {
        assert(false);
        const vector<OverloadPtr> *ptr = NULL;
        return *ptr;
    }
    }
}

static void convertAliasToDeclaration(GlobalAlias &GA, Module &M) {
  GlobalValue *GVal = GA.getBaseObject();
  GlobalValue *NewGV;
  if (auto *GVar = dyn_cast<GlobalVariable>(GVal)) {
    GlobalVariable *NewGVar = new GlobalVariable(
        M, GVar->getType()->getElementType(), GVar->isConstant(),
        GVar->getLinkage(), /*init*/ nullptr, GA.getName(), GVar,
        GVar->getThreadLocalMode(), GVar->getType()->getAddressSpace());
    NewGV = NewGVar;
    NewGV->copyAttributesFrom(GVar);
  } else {
    auto *F = dyn_cast<Function>(GVal);
    assert(F);
    Function *NewF = Function::Create(F->getFunctionType(), F->getLinkage(),
                                      GA.getName(), &M);
    NewGV = NewF;
    NewGV->copyAttributesFrom(F);
  }
  GA.replaceAllUsesWith(ConstantExpr::getBitCast(NewGV, GA.getType()));
  GA.eraseFromParent();
}

LLVMValueRef LLVM_General_GetNextAlias(LLVMValueRef a) {
	GlobalAlias *alias = unwrap<GlobalAlias>(a);
	Module::alias_iterator i = alias;
	if (++i == alias->getParent()->alias_end()) return 0;
	return wrap(i);
}

DyckVertex* AAAnalyzer::wrapValue(Value * v) {
    // if the vertex of v exists, return it, otherwise create one
    pair < DyckVertex*, bool> retpair = dgraph->retrieveDyckVertex(v);
    if (retpair.second) {
        return retpair.first;
    }
    DyckVertex* vdv = retpair.first;
    // constantTy are handled as below.
    if (isa<ConstantExpr>(v)) {
        // constant expr should be handled like a assignment instruction
        if (isa<GEPOperator>(v)) {
            DyckVertex * got = handle_gep((GEPOperator*) v);
            makeAlias(vdv, got);
        } else if (((ConstantExpr*) v)->isCast()) {
            // errs() << *v << "\n";
            DyckVertex * got = wrapValue(((ConstantExpr*) v)->getOperand(0));
            makeAlias(vdv, got);
        } else {
            unsigned opcode = ((ConstantExpr*) v)->getOpcode();
            switch (opcode) {
                case 23: // BinaryConstantExpr "and"
                case 24: // BinaryConstantExpr "or"
                {
                    // do nothing
                }
                    break;
                default:
                {
                    errs() << "ERROR when handle the following constant expression\n";
                    errs() << *v << "\n";
                    errs() << ((ConstantExpr*) v)->getOpcode() << "\n";
                    errs() << ((ConstantExpr*) v)->getOpcodeName() << "\n";
                    errs().flush();
                    exit(-1);
                }
                    break;
            }
        }
    } else if (isa<ConstantArray>(v)) {
#ifndef ARRAY_SIMPLIFIED
        DyckVertex* ptr = addPtrTo(NULL, vdv, dgraph);
        DyckVertex* current = ptr;

        Constant * vAgg = (Constant*) v;
        int numElmt = vAgg->getNumOperands();
        for (int i = 0; i < numElmt; i++) {
            Value * vi = vAgg->getOperand(i);
            DyckVertex* viptr = addPtrOffset(current, i * dl.getTypeAllocSize(vi->getType()), dgraph);
            addPtrTo(viptr, wrapValue(vi, dgraph, dl), dgraph);
        }
#else
        Constant * vAgg = (Constant*) v;
        int numElmt = vAgg->getNumOperands();
        for (int i = 0; i < numElmt; i++) {
            Value * vi = vAgg->getOperand(i);
            makeAlias(vdv, wrapValue(vi));
        }
#endif
    } else if (isa<ConstantStruct>(v)) {
        //DyckVertex* ptr = addPtrTo(NULL, vdv);
        //DyckVertex* current = ptr;

        Constant * vAgg = (Constant*) v;
        int numElmt = vAgg->getNumOperands();
        for (int i = 0; i < numElmt; i++) {
            Value * vi = vAgg->getOperand(i);
            addField(vdv, -2 - i, wrapValue(vi));
        }
    } else if (isa<GlobalValue>(v)) {
        if (isa<GlobalVariable>(v)) {
            GlobalVariable * global = (GlobalVariable *) v;
            if (global->hasInitializer()) {
                Value * initializer = global->getInitializer();
                if (!isa<UndefValue>(initializer)) {
                    DyckVertex * initVer = wrapValue(initializer);
                    addPtrTo(vdv, initVer);
                }
            }
        } else if (isa<GlobalAlias>(v)) {
            GlobalAlias * global = (GlobalAlias *) v;
            Value * aliasee = global->getAliasee();
            makeAlias(vdv, wrapValue(aliasee));
        } else if (isa<Function>(v)) {
            // do nothing
        } // no else
    } else if (isa<ConstantInt>(v) || isa<ConstantFP>(v) || isa<ConstantPointerNull>(v) || isa<UndefValue>(v)) {
        // do nothing
    } else if (isa<ConstantDataArray>(v) || isa<ConstantAggregateZero>(v)) {
        // do nothing
    } else if (isa<BlockAddress>(v)) {
        // do nothing
    } else if (isa<ConstantDataVector>(v)) {
        errs() << "ERROR when handle the following ConstantDataSequential, ConstantDataVector\n";
        errs() << *v << "\n";
        errs().flush();
        exit(-1);
    } else if (isa<ConstantVector>(v)) {
        errs() << "ERROR when handle the following ConstantVector\n";
        errs() << *v << "\n";
        errs().flush();
//.........这里部分代码省略.........

/// Given a disjoint set of bitsets and globals, layout the globals, build the
/// bit sets and lower the llvm.bitset.test calls.
void LowerBitSets::buildBitSetsFromGlobalVariables(
    ArrayRef<Metadata *> BitSets, ArrayRef<GlobalVariable *> Globals) {
  // Build a new global with the combined contents of the referenced globals.
  // This global is a struct whose even-indexed elements contain the original
  // contents of the referenced globals and whose odd-indexed elements contain
  // any padding required to align the next element to the next power of 2.
  std::vector<Constant *> GlobalInits;
  const DataLayout &DL = M->getDataLayout();
  for (GlobalVariable *G : Globals) {
    GlobalInits.push_back(G->getInitializer());
    uint64_t InitSize = DL.getTypeAllocSize(G->getValueType());

    // Compute the amount of padding required.
    uint64_t Padding = NextPowerOf2(InitSize - 1) - InitSize;

    // Cap at 128 was found experimentally to have a good data/instruction
    // overhead tradeoff.
    if (Padding > 128)
      Padding = RoundUpToAlignment(InitSize, 128) - InitSize;

    GlobalInits.push_back(
        ConstantAggregateZero::get(ArrayType::get(Int8Ty, Padding)));
  }
  if (!GlobalInits.empty())
    GlobalInits.pop_back();
  Constant *NewInit = ConstantStruct::getAnon(M->getContext(), GlobalInits);
  auto *CombinedGlobal =
      new GlobalVariable(*M, NewInit->getType(), /*isConstant=*/true,
                         GlobalValue::PrivateLinkage, NewInit);

  StructType *NewTy = cast<StructType>(NewInit->getType());
  const StructLayout *CombinedGlobalLayout = DL.getStructLayout(NewTy);

  // Compute the offsets of the original globals within the new global.
  DenseMap<GlobalObject *, uint64_t> GlobalLayout;
  for (unsigned I = 0; I != Globals.size(); ++I)
    // Multiply by 2 to account for padding elements.
    GlobalLayout[Globals[I]] = CombinedGlobalLayout->getElementOffset(I * 2);

  lowerBitSetCalls(BitSets, CombinedGlobal, GlobalLayout);

  // Build aliases pointing to offsets into the combined global for each
  // global from which we built the combined global, and replace references
  // to the original globals with references to the aliases.
  for (unsigned I = 0; I != Globals.size(); ++I) {
    // Multiply by 2 to account for padding elements.
    Constant *CombinedGlobalIdxs[] = {ConstantInt::get(Int32Ty, 0),
                                      ConstantInt::get(Int32Ty, I * 2)};
    Constant *CombinedGlobalElemPtr = ConstantExpr::getGetElementPtr(
        NewInit->getType(), CombinedGlobal, CombinedGlobalIdxs);
    if (LinkerSubsectionsViaSymbols) {
      Globals[I]->replaceAllUsesWith(CombinedGlobalElemPtr);
    } else {
      assert(Globals[I]->getType()->getAddressSpace() == 0);
      GlobalAlias *GAlias = GlobalAlias::create(NewTy->getElementType(I * 2), 0,
                                                Globals[I]->getLinkage(), "",
                                                CombinedGlobalElemPtr, M);
      GAlias->setVisibility(Globals[I]->getVisibility());
      GAlias->takeName(Globals[I]);
      Globals[I]->replaceAllUsesWith(GAlias);
    }
    Globals[I]->eraseFromParent();
  }
}

SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) {
  if (GA.isInterposable())
    return unknown();
  return compute(GA.getAliasee());
}

static bool isAliasToDeclaration(const GlobalAlias &V) {
  return isDeclaration(*V.getAliasedGlobal());
}