首先这是对一个LTS版本内llvm组件的升级，从7.0升级到8.0.1的话，解决了什么问题？ 如果按邮件描述的，”llvm社区对老版本不做维护，社区甚至不会做bugfix”。那升级到8.0.1不解决问题？
其次，要分析下升级的影响范围。 在当前LTS版本内，有哪些软件是直接或者依赖llvm，哪些会因为llvm的升级做相应的变动。 比如llvm升级，compiler-rt, clang不升吗？clang升级，lldb不升吗？ 这个升级的变动范围会在哪里截止？
再然后是分析下升级时需要受影响组件做什么变更？ 是直接二进制兼容？还是需要重新编译？还是需要代码上做调整？性能有什么影响？功能有什么影响？ 这个会需要扩散到本次升级影响范围内的所有包。
当前分析不能支撑TC在会议上做有效讨论。
Regards Xinwei
From: shenyangyang Sent: Monday, August 3, 2020 9:07 PM To: Huxinwei huxinwei@huawei.com; tc@openeuler.org; guoge (A) guoge1@huawei.com Subject: 答复: 请求评审LTS的LLVM升级到8.0.1
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.commailto:shenyangyang4@huawei.com>; tc@openeuler.orgmailto: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.orgmailto: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.commailto:shenyangyang4@huawei.com [cid:image001.png@01D6076C.F37B6120]
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