C++ GlobalVariable::setConstant方法代码示例

  GlobalVariable*
  materializeStringLiteral(llvm::Module& m, const char* data)
  {
    Constant* ary = llvm::ConstantDataArray::getString(m.getContext(), data, true);
    GlobalVariable* gv = new GlobalVariable(m, ary->getType(), true, GlobalValue::LinkageTypes::PrivateLinkage, ary, "");
    gv->setConstant(true);

    return gv;
  }

//
// Method: runOnModule()
//
// Description:
//  Entry point for this LLVM pass.
//
// Return value:
//  true  - The module was modified.
//  false - The module was not modified.
//
bool
BreakConstantStrings::runOnModule (Module & M) {
  bool modified = false;
  const Type * Int8Type  = IntegerType::getInt8Ty(getGlobalContext());

  //
  // Scan through all the global variables in the module.  Mark a variable as
  // non-constant if:
  //  o) The variable is constant
  //  o) The variable is an array of characters (Int8Ty).
  //  o) The variable is not in a special section (e.g. debug info section).
  //     This ensures that we don't mess up debug information or other special
  //     strings within the code.
  //
  Module::global_iterator i,e;
  for (i = M.global_begin(), e = M.global_end(); i != e; ++i) {
    GlobalVariable * GV = i;

    //
    // All global variables are pointer types.  Find the type of what the
    // global variable pointer is pointing at.
    //
    if (GV->isConstant() && (!GV->hasSection())) {
      const PointerType * PT = dyn_cast<PointerType>(GV->getType());
      if (const ArrayType * AT = dyn_cast<ArrayType>(PT->getElementType())) {
        if (AT->getElementType() == Int8Type) {
          modified = true;
          ++GVChanges;
          GV->setConstant (false);
        }
      }
    }
  }

  return modified;
}

void CodeGen_GPU_Host<CodeGen_CPU>::compile(Stmt stmt, string name,
                                            const vector<Argument> &args,
                                            const vector<Buffer> &images_to_embed) {

    init_module();

    // also set up the child codegenerator - this is set up once per
    // PTX_Host::compile, and reused across multiple PTX_Dev::compile
    // invocations for different kernels.
    cgdev->init_module();

    module = get_initial_module_for_target(target, context);

    // grab runtime helper functions


    // Fix the target triple
    debug(1) << "Target triple of initial module: " << module->getTargetTriple() << "\n";

    llvm::Triple triple = CodeGen_CPU::get_target_triple();
    module->setTargetTriple(triple.str());

    debug(1) << "Target triple of initial module: " << module->getTargetTriple() << "\n";

    // Pass to the generic codegen
    CodeGen::compile(stmt, name, args, images_to_embed);

    // Unset constant flag for embedded image global variables
    for (size_t i = 0; i < images_to_embed.size(); i++) {
        string name = images_to_embed[i].name();
        GlobalVariable *global = module->getNamedGlobal(name + ".buffer");
        global->setConstant(false);
    }

    std::vector<char> kernel_src = cgdev->compile_to_src();

    Value *kernel_src_ptr = CodeGen_CPU::create_constant_binary_blob(kernel_src, "halide_kernel_src");

    // Remember the entry block so we can branch to it upon init success.
    BasicBlock *entry = &function->getEntryBlock();

    // Insert a new block to run initialization at the beginning of the function.
    BasicBlock *init_kernels_bb = BasicBlock::Create(*context, "init_kernels",
                                                     function, entry);
    builder->SetInsertPoint(init_kernels_bb);
    Value *user_context = get_user_context();
    Value *kernel_size = ConstantInt::get(i32, kernel_src.size());
    Value *init = module->getFunction("halide_init_kernels");
    internal_assert(init) << "Could not find function halide_init_kernels in initial module\n";
    Value *result = builder->CreateCall4(init, user_context,
                                         get_module_state(),
                                         kernel_src_ptr, kernel_size);
    Value *did_succeed = builder->CreateICmpEQ(result, ConstantInt::get(i32, 0));
    CodeGen_CPU::create_assertion(did_succeed, "Failure inside halide_init_kernels");

    // Upon success, jump to the original entry.
    builder->CreateBr(entry);

    // Optimize the module
    CodeGen::optimize_module();
}

Module *llvm::CloneModule(const Module *M,
                          DenseMap<const Value*, Value*> &ValueMap) {
  // First off, we need to create the new module...
  Module *New = new Module(M->getModuleIdentifier());
  New->setDataLayout(M->getDataLayout());
  New->setTargetTriple(M->getTargetTriple());
  New->setModuleInlineAsm(M->getModuleInlineAsm());

  // Copy all of the type symbol table entries over.
  const TypeSymbolTable &TST = M->getTypeSymbolTable();
  for (TypeSymbolTable::const_iterator TI = TST.begin(), TE = TST.end(); 
       TI != TE; ++TI)
    New->addTypeName(TI->first, TI->second);
  
  // Copy all of the dependent libraries over.
  for (Module::lib_iterator I = M->lib_begin(), E = M->lib_end(); I != E; ++I)
    New->addLibrary(*I);

  // Loop over all of the global variables, making corresponding globals in the
  // new module.  Here we add them to the ValueMap and to the new Module.  We
  // don't worry about attributes or initializers, they will come later.
  //
  for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I) {
    GlobalVariable *GV = new GlobalVariable(I->getType()->getElementType(),
                                            false,
                                            GlobalValue::ExternalLinkage, 0,
                                            I->getName(), New);
    GV->setAlignment(I->getAlignment());
    ValueMap[I] = GV;
  }

  // Loop over the functions in the module, making external functions as before
  for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I) {
    Function *NF =
      Function::Create(cast<FunctionType>(I->getType()->getElementType()),
                       GlobalValue::ExternalLinkage, I->getName(), New);
    NF->copyAttributesFrom(I);
    ValueMap[I] = NF;
  }

  // Loop over the aliases in the module
  for (Module::const_alias_iterator I = M->alias_begin(), E = M->alias_end();
       I != E; ++I)
    ValueMap[I] = new GlobalAlias(I->getType(), GlobalAlias::ExternalLinkage,
                                  I->getName(), NULL, New);
  
  // Now that all of the things that global variable initializer can refer to
  // have been created, loop through and copy the global variable referrers
  // over...  We also set the attributes on the global now.
  //
  for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I) {
    GlobalVariable *GV = cast<GlobalVariable>(ValueMap[I]);
    if (I->hasInitializer())
      GV->setInitializer(cast<Constant>(MapValue(I->getInitializer(),
                                                 ValueMap)));
    GV->setLinkage(I->getLinkage());
    GV->setThreadLocal(I->isThreadLocal());
    GV->setConstant(I->isConstant());
  }

  // Similarly, copy over function bodies now...
  //
  for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I) {
    Function *F = cast<Function>(ValueMap[I]);
    if (!I->isDeclaration()) {
      Function::arg_iterator DestI = F->arg_begin();
      for (Function::const_arg_iterator J = I->arg_begin(); J != I->arg_end();
           ++J) {
        DestI->setName(J->getName());
        ValueMap[J] = DestI++;
      }

      std::vector<ReturnInst*> Returns;  // Ignore returns cloned...
      CloneFunctionInto(F, I, ValueMap, Returns);
    }

    F->setLinkage(I->getLinkage());
  }

  // And aliases
  for (Module::const_alias_iterator I = M->alias_begin(), E = M->alias_end();
       I != E; ++I) {
    GlobalAlias *GA = cast<GlobalAlias>(ValueMap[I]);
    GA->setLinkage(I->getLinkage());
    if (const Constant* C = I->getAliasee())
      GA->setAliasee(cast<Constant>(MapValue(C, ValueMap)));
  }
  
  return New;
}

Module *llvm::CloneModule(const Module *M,
                          ValueToValueMapTy &VMap) {
  // First off, we need to create the new module...
  Module *New = new Module(M->getModuleIdentifier(), M->getContext());
  New->setDataLayout(M->getDataLayout());
  New->setTargetTriple(M->getTargetTriple());
  New->setModuleInlineAsm(M->getModuleInlineAsm());

  // Copy all of the type symbol table entries over.
  const TypeSymbolTable &TST = M->getTypeSymbolTable();
  for (TypeSymbolTable::const_iterator TI = TST.begin(), TE = TST.end(); 
       TI != TE; ++TI)
    New->addTypeName(TI->first, TI->second);
  
  // Copy all of the dependent libraries over.
  for (Module::lib_iterator I = M->lib_begin(), E = M->lib_end(); I != E; ++I)
    New->addLibrary(*I);

  // Loop over all of the global variables, making corresponding globals in the
  // new module.  Here we add them to the VMap and to the new Module.  We
  // don't worry about attributes or initializers, they will come later.
  //
  for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I) {
    GlobalVariable *GV = new GlobalVariable(*New, 
                                            I->getType()->getElementType(),
                                            false,
                                            GlobalValue::ExternalLinkage, 0,
                                            I->getName());
    GV->setAlignment(I->getAlignment());
    VMap[I] = GV;
  }

  // Loop over the functions in the module, making external functions as before
  for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I) {
    Function *NF =
      Function::Create(cast<FunctionType>(I->getType()->getElementType()),
                       GlobalValue::ExternalLinkage, I->getName(), New);
    NF->copyAttributesFrom(I);
    VMap[I] = NF;
  }

  // Loop over the aliases in the module
  for (Module::const_alias_iterator I = M->alias_begin(), E = M->alias_end();
       I != E; ++I)
    VMap[I] = new GlobalAlias(I->getType(), GlobalAlias::ExternalLinkage,
                                  I->getName(), NULL, New);
  
  // Now that all of the things that global variable initializer can refer to
  // have been created, loop through and copy the global variable referrers
  // over...  We also set the attributes on the global now.
  //
  for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I) {
    GlobalVariable *GV = cast<GlobalVariable>(VMap[I]);
    if (I->hasInitializer())
      GV->setInitializer(cast<Constant>(MapValue(I->getInitializer(),
                                                 VMap)));
    GV->setLinkage(I->getLinkage());
    GV->setThreadLocal(I->isThreadLocal());
    GV->setConstant(I->isConstant());
  }

  // Similarly, copy over function bodies now...
  //
  for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I) {
    Function *F = cast<Function>(VMap[I]);
    if (!I->isDeclaration()) {
      Function::arg_iterator DestI = F->arg_begin();
      for (Function::const_arg_iterator J = I->arg_begin(); J != I->arg_end();
           ++J) {
        DestI->setName(J->getName());
        VMap[J] = DestI++;
      }

      SmallVector<ReturnInst*, 8> Returns;  // Ignore returns cloned.
      CloneFunctionInto(F, I, VMap, Returns);
    }

    F->setLinkage(I->getLinkage());
  }

  // And aliases
  for (Module::const_alias_iterator I = M->alias_begin(), E = M->alias_end();
       I != E; ++I) {
    GlobalAlias *GA = cast<GlobalAlias>(VMap[I]);
    GA->setLinkage(I->getLinkage());
    if (const Constant* C = I->getAliasee())
      GA->setAliasee(cast<Constant>(MapValue(C, VMap)));
  }

  // And named metadata....
  for (Module::const_named_metadata_iterator I = M->named_metadata_begin(),
         E = M->named_metadata_end(); I != E; ++I) {
    const NamedMDNode &NMD = *I;
    SmallVector<MDNode*, 4> MDs;
    for (unsigned i = 0, e = NMD.getNumOperands(); i != e; ++i)
      MDs.push_back(cast<MDNode>(MapValue(NMD.getOperand(i), VMap)));
    NamedMDNode::Create(New->getContext(), NMD.getName(),
                        MDs.data(), MDs.size(), New);
//.........这里部分代码省略.........

//.........这里部分代码省略.........
      GV = new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage, 0,
                              "", TheModule);

      // Check for external weak linkage
      if (DECL_EXTERNAL(decl) && DECL_WEAK(decl))
        GV->setLinkage(GlobalValue::ExternalWeakLinkage);
      
#ifdef TARGET_ADJUST_LLVM_LINKAGE
      TARGET_ADJUST_LLVM_LINKAGE(GV,decl);
#endif /* TARGET_ADJUST_LLVM_LINKAGE */

      // Handle visibility style
      if (TREE_PUBLIC(decl)) {
        if (DECL_VISIBILITY(decl) == VISIBILITY_HIDDEN)
          GV->setVisibility(GlobalValue::HiddenVisibility);
        else if (DECL_VISIBILITY(decl) == VISIBILITY_PROTECTED)
          GV->setVisibility(GlobalValue::ProtectedVisibility);
      }

    } else {
      // If the global has a name, prevent multiple vars with the same name from
      // being created.
      GlobalVariable *GVE = TheModule->getGlobalVariable(Name);
    
      if (GVE == 0) {
        GV = new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage,0,
                                Name, TheModule);

        // Check for external weak linkage
        if (DECL_EXTERNAL(decl) && DECL_WEAK(decl))
          GV->setLinkage(GlobalValue::ExternalWeakLinkage);
        
#ifdef TARGET_ADJUST_LLVM_LINKAGE
        TARGET_ADJUST_LLVM_LINKAGE(GV,decl);
#endif /* TARGET_ADJUST_LLVM_LINKAGE */

        // Handle visibility style
        if (TREE_PUBLIC(decl)) {
          if (DECL_VISIBILITY(decl) == VISIBILITY_HIDDEN)
            GV->setVisibility(GlobalValue::HiddenVisibility);
          else if (DECL_VISIBILITY(decl) == VISIBILITY_PROTECTED)
            GV->setVisibility(GlobalValue::ProtectedVisibility);
        }

        // If GV got renamed, then there is already an object with this name in
        // the symbol table.  If this happens, the old one must be a forward
        // decl, just replace it with a cast of the new one.
        if (GV->getName() != Name) {
          Function *F = TheModule->getFunction(Name);
          assert(F && F->isDeclaration() && "A function turned into a global?");
          
          // Replace any uses of "F" with uses of GV.
          Value *FInNewType = ConstantExpr::getBitCast(GV, F->getType());
          F->replaceAllUsesWith(FInNewType);
          
          // Update the decl that points to F.
          changeLLVMValue(F, FInNewType);

          // Now we can give GV the proper name.
          GV->takeName(F);
          
          // F is now dead, nuke it.
          F->eraseFromParent();
        }
        
      } else {
        GV = GVE;  // Global already created, reuse it.
      }
    }
    
    if ((TREE_READONLY(decl) && !TREE_SIDE_EFFECTS(decl)) || 
        TREE_CODE(decl) == CONST_DECL) {
      if (DECL_EXTERNAL(decl)) {
        // Mark external globals constant even though they could be marked
        // non-constant in the defining translation unit.  The definition of the
        // global determines whether the global is ultimately constant or not,
        // marking this constant will allow us to do some extra (legal)
        // optimizations that we would otherwise not be able to do.  (In C++,
        // any global that is 'C++ const' may not be readonly: it could have a
        // dynamic initializer.
        //
        GV->setConstant(true);
      } else {
        // Mark readonly globals with constant initializers constant.
        if (DECL_INITIAL(decl) != error_mark_node && // uninitialized?
            DECL_INITIAL(decl) &&
            (TREE_CONSTANT(DECL_INITIAL(decl)) ||
             TREE_CODE(DECL_INITIAL(decl)) == STRING_CST))
          GV->setConstant(true);
      }
    }

    // Set thread local (TLS)
    if (TREE_CODE(decl) == VAR_DECL && DECL_THREAD_LOCAL(decl))
      GV->setThreadLocal(true);

    SET_DECL_LLVM(decl, GV);
  }
  timevar_pop(TV_LLVM_GLOBALS);
}

bool LowerEmuTLS::addEmuTlsVar(Module &M, const GlobalVariable *GV) {
  LLVMContext &C = M.getContext();
  PointerType *VoidPtrType = Type::getInt8PtrTy(C);

  std::string EmuTlsVarName = ("__emutls_v." + GV->getName()).str();
  GlobalVariable *EmuTlsVar = M.getNamedGlobal(EmuTlsVarName);
  if (EmuTlsVar)
    return false;  // It has been added before.

  const DataLayout &DL = M.getDataLayout();
  Constant *NullPtr = ConstantPointerNull::get(VoidPtrType);

  // Get non-zero initializer from GV's initializer.
  const Constant *InitValue = nullptr;
  if (GV->hasInitializer()) {
    InitValue = GV->getInitializer();
    const ConstantInt *InitIntValue = dyn_cast<ConstantInt>(InitValue);
    // When GV's init value is all 0, omit the EmuTlsTmplVar and let
    // the emutls library function to reset newly allocated TLS variables.
    if (isa<ConstantAggregateZero>(InitValue) ||
        (InitIntValue && InitIntValue->isZero()))
      InitValue = nullptr;
  }

  // Create the __emutls_v. symbol, whose type has 4 fields:
  //     word size;   // size of GV in bytes
  //     word align;  // alignment of GV
  //     void *ptr;   // initialized to 0; set at run time per thread.
  //     void *templ; // 0 or point to __emutls_t.*
  // sizeof(word) should be the same as sizeof(void*) on target.
  IntegerType *WordType = DL.getIntPtrType(C);
  PointerType *InitPtrType = InitValue ?
      PointerType::getUnqual(InitValue->getType()) : VoidPtrType;
  Type *ElementTypes[4] = {WordType, WordType, VoidPtrType, InitPtrType};
  ArrayRef<Type*> ElementTypeArray(ElementTypes, 4);
  StructType *EmuTlsVarType = StructType::create(ElementTypeArray);
  EmuTlsVar = cast<GlobalVariable>(
      M.getOrInsertGlobal(EmuTlsVarName, EmuTlsVarType));
  copyLinkageVisibility(M, GV, EmuTlsVar);

  // Define "__emutls_t.*" and "__emutls_v.*" only if GV is defined.
  if (!GV->hasInitializer())
    return true;

  Type *GVType = GV->getValueType();
  unsigned GVAlignment = GV->getAlignment();
  if (!GVAlignment) {
    // When LLVM IL declares a variable without alignment, use
    // the ABI default alignment for the type.
    GVAlignment = DL.getABITypeAlignment(GVType);
  }

  // Define "__emutls_t.*" if there is InitValue
  GlobalVariable *EmuTlsTmplVar = nullptr;
  if (InitValue) {
    std::string EmuTlsTmplName = ("__emutls_t." + GV->getName()).str();
    EmuTlsTmplVar = dyn_cast_or_null<GlobalVariable>(
        M.getOrInsertGlobal(EmuTlsTmplName, GVType));
    assert(EmuTlsTmplVar && "Failed to create emualted TLS initializer");
    EmuTlsTmplVar->setConstant(true);
    EmuTlsTmplVar->setInitializer(const_cast<Constant*>(InitValue));
    EmuTlsTmplVar->setAlignment(GVAlignment);
    copyLinkageVisibility(M, GV, EmuTlsTmplVar);
  }

  // Define "__emutls_v.*" with initializer and alignment.
  Constant *ElementValues[4] = {
      ConstantInt::get(WordType, DL.getTypeStoreSize(GVType)),
      ConstantInt::get(WordType, GVAlignment),
      NullPtr, EmuTlsTmplVar ? EmuTlsTmplVar : NullPtr
  };
  ArrayRef<Constant*> ElementValueArray(ElementValues, 4);
  EmuTlsVar->setInitializer(
      ConstantStruct::get(EmuTlsVarType, ElementValueArray));
  unsigned MaxAlignment = std::max(
      DL.getABITypeAlignment(WordType),
      DL.getABITypeAlignment(VoidPtrType));
  EmuTlsVar->setAlignment(MaxAlignment);
  return true;
}