从openEuler社区maintainer得知，llvm社区对于老版本是不做维护的，社区甚至不会做bugfix

llvm 8.0.1新增特性：

ORC (On Request Compilation) JIT APIs更新了，支持并发编译，以前的不支持并发编译的接口会被废弃，并且会在LLVM 9以后直接被移除

对AArch64增加了新特性：

支持Speculative Load Hardening（有效防止信息泄露）函数属性

.arch_extension像arm一样增加对汇编指令的支持

开始支持Tiny代码模型

头文件以及abi变更：

1.删除IndirectCallSiteVisitor.h，GCs.h，NativeBuiltinSymbol.h，NativeEnumSymbol.h，TypeBuilder.h，OrderedInstructions.h头文件

2.include\llvm\Analysis\AliasSetTracker.h头文件删除AliasSet &getAliasSetForPointer，AliasSet *getAliasSetForPointerIfExists，bool containsUnknown三个函数；AliasSet &addPointer(Value *P, LocationSize Size, const AAMDNodes &AAInfo,AliasSet::AccessLattice E)变更为 AliasSet &addPointer(MemoryLocation Loc, AliasSet::AccessLattice E)""

3.include\llvm\Analysis\CmpInstAnalysis.h头文件*getICmpValue(bool Sign, unsigned Code, Value *LHS, Value *RHS,CmpInst::Predicate &NewICmpPred)变更为Constant *getPredForICmpCode(unsigned Code, bool Sign, Type *OpTy,CmpInst::Predicate &Pred);

4.include\llvm\Analysis\DemandedBits.h文件determineLiveOperandBits函数新增参数bool &KnownBitsComputed

5.include\llvm\Analysis\BlockFrequencyInfo.h文件中void view()有默认参数void view(StringRef = ""BlockFrequencyDAGs"")

6.删除了usr/lib64/BugpointPasses.so、LLVMHello.so、TestPlugin.so，新增libOptRemarks.so.8

7.include\llvm\Analysis\MemorySSA.h：createNewAccess(Instruction *)变更为createNewAccess(Instruction *,const MemoryUseOrDef *Template = nullptr);createDefinedAccess(Instruction *, MemoryAccess *)变更为createDefinedAccess(Instruction *, MemoryAccess *,const MemoryUseOrDef *Template = nullptr)

8.include\llvm\Analysis\MemorySSAUpdater.h:wireOldPredecessorsToNewImmediatePredecessor(BasicBlock *Old, BasicBlock *New,ArrayRef<BasicBlock *> Preds)变更为wireOldPredecessorsToNewImmediatePredecessor(BasicBlock *Old, BasicBlock *New, ArrayRef<BasicBlock *> Preds,bool IdenticalEdgesWereMerged = true);

9.Analysis\MustExecute.h文件computeLoopSafetyInfo(LoopSafetyInfo *, Loop *)变更为computeLoopSafetyInfo(const Loop *CurLoop)；删除了isGuaranteedToExecute

10.Analysis\Passes.h文件createDivergenceAnalysisPass()变更为createLegacyDivergenceAnalysisPass

11.Analysis\ProfileSummaryInfo.h文件isHotBB变更为isHotBlock；isColdBB变更为isColdBlock

12.include\llvm\Analysis\CaptureTracking.h文件中PointerMayBeCapturedBefore函数新增参数unsigned MaxUsesToExplore = DefaultMaxUsesToExplore

13.Analysis\TypeMetadataUtils.h文件findDevirtualizableCallsForTypeTest函数增加DominatorTree &DT参数

14.BinaryFormat\Dwarf.h文件CallFrameString(unsigned Encoding)变更为CallFrameString(unsigned Encoding, Triple::ArchType Arch)

15.BinaryFormat\Wasm.h删除结构体WasmSignature，新增结构体WasmDylinkInfo；修改结构体WasmSymbolInfo

16.CodeGen\GlobalISel\MachineIRBuilder.h文件删除void recordInsertion、void recordInsertions以及void stopRecordingInsertions函数

17.llvm\CodeGen\GCMetadata.h文件void addSafePoint参数减少了GC::PointKind Kind

18.llvm\CodeGen\MachineFunction.h文件删除addLandingPadInfo函数

19.llvm\CodeGen\MachineInstr.h文件删除了getNumMemOperands、setMemRefs、dropMemRefs函数

20.llvm\CodeGen\MachineScheduler.h文件biasPhysRegCopy变更为biasPhysReg

21.llvm\CodeGen\SlotIndexes.h文件中llvm::sort(idx2MBBMap.begin(), idx2MBBMap.end(), Idx2MBBCompare())变更为llvm::sort(idx2MBBMap, Idx2MBBCompare())

22.DebugInfo\CodeView\TypeStreamMerger.h文件中mergeTypeAndIdRecords、mergeTypeAndIdRecords、mergeTypeRecords函数均增加一个形参Optional<uint32_t> &PCHSignature

23.llvm\ExecutionEngine\JITEventListener.h文件中删除结构体JITEvent_EmittedFunctionDetails

24.llvm\IR\InstrTypes.h文件删除TerminatorInst、FuncletPadInst类

25.llvm\IR\LegacyPassManager.h文件删除了reportAndResetTimings函数

26.llvm\LTO\LTO.h文件thinLTOResolveWeakForLinkerInIndex函数变更为thinLTOResolvePrevailingInIndex

27.llvm\Object\ELF.h文件将getELFRelrRelocationType变更为getELFRelativeRelocationType，getRelrRelocationType变更为getRelativeRelocationType

28.llvm\ProfileData\InstrProf.h文件llvm::sort函数将MD5NameMap.begin(), MD5NameMap.end()参数变成MD5NameMap

29.Transforms\IPO\FunctionImport.h文件thinLTOResolveWeakForLinkerModule变更为thinLTOResolvePrevailingInModule

30.Transforms\Instrumentation.h文件删除了createMemorySanitizerPass、createThreadSanitizerPass函数

31.Transforms\Scalar.h文件删除了createScalarizerPass函数

32.llvm-c\ExecutionEngine.h文件函数LLVMCreateOprofileJITEventListener变更为LLVMCreateOProfileJITEventListener

33.include\llvm\ADT\StringExtras.h头文件inline std::string toHex(StringRef Input)增加了一个默认参数inline std::string toHex(StringRef Input, bool LowerCase = false)

34.include\llvm\ADT\STLExtras.h删除模板函数template <typename R>auto size

利用abichecker对llvm-libs子包也进行了测试，主要abi变更见下

35./usr/lib64/LLVMgold.so删除了function void onload()

1 Removed function:

  'function void onload()'    {onload@@LLVM_7}

36."libLTO.so.7到libLTO.so.8移除了67个函数

'function void lto_api_version()'    {lto_api_version@@LLVM_7}

  'function void lto_codegen_add_module()'    {lto_codegen_add_module@@LLVM_7}

  'function void lto_codegen_add_must_preserve_symbol()'    {lto_codegen_add_must_preserve_symbol@@LLVM_7}

  'function void lto_codegen_compile()'    {lto_codegen_compile@@LLVM_7}

  'function void lto_codegen_compile_optimized()'    {lto_codegen_compile_optimized@@LLVM_7}

  'function void lto_codegen_compile_to_file()'    {lto_codegen_compile_to_file@@LLVM_7}

  'function void lto_codegen_create()'    {lto_codegen_create@@LLVM_7}

  'function void lto_codegen_create_in_local_context()'    {lto_codegen_create_in_local_context@@LLVM_7}

  'function void lto_codegen_debug_options()'    {lto_codegen_debug_options@@LLVM_7}

  'function void lto_codegen_dispose()'    {lto_codegen_dispose@@LLVM_7}

  'function void lto_codegen_optimize()'    {lto_codegen_optimize@@LLVM_7}

  'function void lto_codegen_set_assembler_args()'    {lto_codegen_set_assembler_args@@LLVM_7}

  'function void lto_codegen_set_assembler_path()'    {lto_codegen_set_assembler_path@@LLVM_7}

  'function void lto_codegen_set_cpu()'    {lto_codegen_set_cpu@@LLVM_7}

  'function void lto_codegen_set_debug_model()'    {lto_codegen_set_debug_model@@LLVM_7}

  'function void lto_codegen_set_diagnostic_handler()'    {lto_codegen_set_diagnostic_handler@@LLVM_7}

  'function void lto_codegen_set_module()'    {lto_codegen_set_module@@LLVM_7}

  'function void lto_codegen_set_pic_model()'    {lto_codegen_set_pic_model@@LLVM_7}

  'function void lto_codegen_set_should_embed_uselists()'    {lto_codegen_set_should_embed_uselists@@LLVM_7}

  'function void lto_codegen_set_should_internalize()'    {lto_codegen_set_should_internalize@@LLVM_7}

  'function void lto_codegen_write_merged_modules()'    {lto_codegen_write_merged_modules@@LLVM_7}

  'function void lto_get_error_message()'    {lto_get_error_message@@LLVM_7}

  'function void lto_get_version()'    {lto_get_version@@LLVM_7}

  'function void lto_initialize_disassembler()'    {lto_initialize_disassembler@@LLVM_7}

  'function void lto_module_create()'    {lto_module_create@@LLVM_7}

  'function void lto_module_create_from_fd()'    {lto_module_create_from_fd@@LLVM_7}

  'function void lto_module_create_from_fd_at_offset()'    {lto_module_create_from_fd_at_offset@@LLVM_7}

  'function void lto_module_create_from_memory()'    {lto_module_create_from_memory@@LLVM_7}

  'function void lto_module_create_from_memory_with_path()'    {lto_module_create_from_memory_with_path@@LLVM_7}

  'function void lto_module_create_in_codegen_context()'    {lto_module_create_in_codegen_context@@LLVM_7}

  'function void lto_module_create_in_local_context()'    {lto_module_create_in_local_context@@LLVM_7}

  'function void lto_module_dispose()'    {lto_module_dispose@@LLVM_7}

  'function void lto_module_get_linkeropts()'    {lto_module_get_linkeropts@@LLVM_7}

  'function void lto_module_get_num_symbols()'    {lto_module_get_num_symbols@@LLVM_7}

  'function void lto_module_get_symbol_attribute()'    {lto_module_get_symbol_attribute@@LLVM_7}

  'function void lto_module_get_symbol_name()'    {lto_module_get_symbol_name@@LLVM_7}

  'function void lto_module_get_target_triple()'    {lto_module_get_target_triple@@LLVM_7}

  'function void lto_module_has_objc_category()'    {lto_module_has_objc_category@@LLVM_7}

  'function void lto_module_is_object_file()'    {lto_module_is_object_file@@LLVM_7}

  'function void lto_module_is_object_file_for_target()'    {lto_module_is_object_file_for_target@@LLVM_7}

  'function void lto_module_is_object_file_in_memory()'    {lto_module_is_object_file_in_memory@@LLVM_7}

  'function void lto_module_is_object_file_in_memory_for_target()'    {lto_module_is_object_file_in_memory_for_target@@LLVM_7}

  'function void lto_module_is_thinlto()'    {lto_module_is_thinlto@@LLVM_7}

  'function void lto_module_set_target_triple()'    {lto_module_set_target_triple@@LLVM_7}

  'function void thinlto_codegen_add_cross_referenced_symbol()'    {thinlto_codegen_add_cross_referenced_symbol@@LLVM_7}

  'function void thinlto_codegen_add_module()'    {thinlto_codegen_add_module@@LLVM_7}

  'function void thinlto_codegen_add_must_preserve_symbol()'    {thinlto_codegen_add_must_preserve_symbol@@LLVM_7}

  'function void thinlto_codegen_disable_codegen()'    {thinlto_codegen_disable_codegen@@LLVM_7}

  'function void thinlto_codegen_dispose()'    {thinlto_codegen_dispose@@LLVM_7}

  'function void thinlto_codegen_process()'    {thinlto_codegen_process@@LLVM_7}

  'function void thinlto_codegen_set_cache_dir()'    {thinlto_codegen_set_cache_dir@@LLVM_7}

  'function void thinlto_codegen_set_cache_entry_expiration()'    {thinlto_codegen_set_cache_entry_expiration@@LLVM_7}

  'function void thinlto_codegen_set_cache_pruning_interval()'    {thinlto_codegen_set_cache_pruning_interval@@LLVM_7}

  'function void thinlto_codegen_set_cache_size_bytes()'    {thinlto_codegen_set_cache_size_bytes@@LLVM_7}

  'function void thinlto_codegen_set_cache_size_files()'    {thinlto_codegen_set_cache_size_files@@LLVM_7}

  'function void thinlto_codegen_set_codegen_only()'    {thinlto_codegen_set_codegen_only@@LLVM_7}

  'function void thinlto_codegen_set_cpu()'    {thinlto_codegen_set_cpu@@LLVM_7}

  'function void thinlto_codegen_set_final_cache_size_relative_to_available_space()'    {thinlto_codegen_set_final_cache_size_relative_to_available_space@@LLVM_7}

  'function void thinlto_codegen_set_pic_model()'    {thinlto_codegen_set_pic_model@@LLVM_7}

  'function void thinlto_codegen_set_savetemps_dir()'    {thinlto_codegen_set_savetemps_dir@@LLVM_7}

  'function void thinlto_create_codegen()'    {thinlto_create_codegen@@LLVM_7}

  'function void thinlto_debug_options()'    {thinlto_debug_options@@LLVM_7}

  'function void thinlto_module_get_num_object_files()'    {thinlto_module_get_num_object_files@@LLVM_7}

  'function void thinlto_module_get_num_objects()'    {thinlto_module_get_num_objects@@LLVM_7}

  'function void thinlto_module_get_object()'    {thinlto_module_get_object@@LLVM_7}

  'function void thinlto_module_get_object_file()'    {thinlto_module_get_object_file@@LLVM_7}

  'function void thinlto_set_generated_objects_dir()'    {thinlto_set_generated_objects_dir@@LLVM_7}，

新增一个函数

'function void thinlto_codegen_set_cache_size_megabytes()'    {thinlto_codegen_set_cache_size_megabytes@@LLVM_8}"

从openEuler社区maintainer得知，llvm社区对于老版本是不做维护的，社区甚至不会做bugfix，所以LTS对于llvm应该是需要有演进的，但是从分析来看，确实llvm对外头文件的变更较多，如果一下升级到10.0.0版本，跨度较大，对外兼容性也较差，所以我是建议升级到8.0.1中间版本，该版本对于aarch64有新增一些特性支持。也请llvm openEuler maintainer进行讨论。

发件人:

Huxinwei
发送时间: 2020年8月3日 15:44
收件人: shenyangyang <shenyangyang4@huawei.com>; tc@openeuler.org
主题: RE: 请求评审LTS的LLVM升级到8.0.1

选型议题需要给出具体的技术理由

只是版本信息的话，对做出技术抉择没有什么帮助。

From: shenyangyang [mailto:shenyangyang4@huawei.com]
Sent: Monday, August 3, 2020 1:13 PM
To: tc@openeuler.org
Subject: [Tc] 请求评审LTS的LLVM升级到8.0.1

当前lts llvm为7.0.0，为2018年9月19日发布版本，较为老旧，希望能够升级到2019年7月19日的8.0.1的版本，到最新版本的话跨度较大，且差异也较多，故而选择中间版本8.0.1。

沈洋洋

庞加莱实验室 [2012实验室]

Tel : +86 18958088172 

Email : shenyangyang4@huawei.com

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