LLVM初探
LLVM是编译器的框架系统,以C++编写而成,用于优化以任意程序语言编写的程序编译时间,链接时间,运行时间,以及空闲时间,对开发这保持开放,并兼容已有的脚本(来自百度百科),它的全称是Low Level Virtual Machine
LLVM的优势
- 以下来自机翻
- LLVM使用具有严格定义语义的简单低级语言。
- 它包括C和C++前端。Java、Scheme和其他语言的前端正在开发中。
- 它包括一个积极的优化器，包括标量、过程间、概要文件驱动和一些简单的循环优化。
- 它支持编译模型，包括链接时间、安装时间、运行时和脱机优化。
- LLVM完全支持精确的垃圾收集。
- LLVM代码生成器相对容易重定目标，并且使用了强大的目标描述语言。
- LLVM有大量的文档，并且托管了各种各样的项目。
- 此外，LLVM还提供了使开发更容易的工具。
- LLVM正在积极发展，并在不断扩展、增强和改进。
- LLVM在OSI批准的“Apache许可证版本2.0”许可证下免费提供。
LLVM适合人群
1.对C和C ++程序的编译时，链接时（过程间）和运行时转换感兴趣的编译器研究人员；
2.对可移植的，与语言无关的指令集和编译框架感兴趣的虚拟机研究人员
3.对编译器/硬件技术感兴趣的架构研究员
4.对静态分析或插桩技术感兴趣的安全研究人员
5.想要快速开发编译器原型的教师或开发人员
6.希望获得更好性能的最终用户开发者
LLVM架构
clang介绍
前面提到过LLVM项目的一个子项目，基于LLVM架构的C/C++/Objective-C编译器前端,它具有以下优点。
- 编译速度快,在部分平台上，Clang的编译速度显著的快过GCC(Debug模式下编译OC速度比GGC快3倍)
- 占用内存小:Clang生成的AST所占用的内存是GCC的五分之一左右
- 模块化设计:Clang采用基于库的模块化设计，易于 IDE 集成及其他用途的重用,如Xcode集成了Clang的很多命令
- 诊断信息可读性强:在编译过程中，Clang 创建并保留了大量详细的元数据 (metadata)，有利于调试和错误报告,类比Xcode编译时生成的中间产物文件,如诊断信息。
- 设计清晰简单，容易理解，易于扩展增强.
Clang与LLVM之间的关系
在LLVM整体架构，前端用的是clang，广义的LLVM是指整个LLVM架构，一般狭义的LLVM指的是LLVM后端（包含代码优化和目标代码生成）,在iOS的构建中,一般把clang作为编译器的前端,LLVM作为后端,负责优化代码,生成不同的平台的目标代码。
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工作流程:
1.目标代码经过clang,进行词法,语法分析,语议分析,生成出版的中间代码
2.然后经过LLVM后端对代码结构进行优化,最终生成目标代码
在Xcode中新建一个OC工程,使用如下命令编译main.c文件
- 查看工作流程
shell xxx@xxxx Test % clang -ccc-print-phases main.m
0: input, "main.m", objective-c. 输入`main.m`文件
1: preprocessor, {0}, objective-c-cpp-output //预备编译，宏定义的代码替换
2: compiler, {1}, ir //编译器编译,生成中间代码
3: backend, {2}, assembler //后端生成目标代码
4: assembler, {3}, object //汇编
5: linker, {4}, image //链接镜像文件(动态库)
6: bind-arch, "x86_64", {5}, image //编译成指定架构,这里采用的是模拟器测试 - 词法分析测试: 代码会被分割为一个个很小的单元,检测语法格式,如匹配大括号是否配对,是否缺少分号结尾。
执行clang -fmodules -E -Xclang -dump-tokens main.m - 语法树-AST: (Abstract Syntax Tree)
执行clang -fmodules -fsyntax-only -Xclang -ast-dump main.m,这里按照递归的方式列出了每个函数和变量的解析(翻译)过程。
LLVM IR
- LLVM的中间代码(IR)有以下3种表示方式,
- text:便于阅读的文本格式，类似于汇编语言，拓展名.ll， $ clang -S -emit-llvm main.m
- memory:内存格式
- bitcode:二进制格式，拓展名.bc，
clang -c -emit-llvm main.m
LLVM和Clang在Xcode中的应用
LLVM overview
Clang overview
LLVM Optimize
LLVM Code generate overview
其他工具的扩展支持
- 可以通过
man clang来查看它的帮助命令,在Xcode点击三角形Run的时候也可以在控制台看到构建的各个步骤.
LLVM LTO Optimize
- LTO:(link Time Optimize), 优化方式主要有以下三种
- 不同文件的inline函数优化
- 清理不需要的代码
- 对程序全局进行优化
- 传统的link方式,多个文件有交集
LTO优化: 相比传统的link,主要是对
.o文件进行优化后,附加一些优化信息,再进行link
Apple内部的构建已经开始广泛使用
- 通常比常规版本中的可执行文件快10%(官方数据提供)
- 通过文件引导优化,Profile Guide Optimize(PGO),按照配置进行优化
- 将频繁调用且依赖性较强的函数专为内联函数
- 虚函数的调用推测,改为直接调用
- 寄存器分配优化
- 条件分支的优化,如switch,将高概率出现的值单独拧出来处理
- 函数布局,将类似指令,功能相关的函数放到相同的section,尽量安排在一起
- 总的来说，就是提高CPU的的缓存命中率和分支预测的成功率。
- 优化大小时减少代码大小
LTO优化需在编译时间和运行性能之间做权衡,优化过度会造成,在debug info的时候非常不方便
- 编译时大量的内存开销
- 优化不是并行运行的
- 增量构建的重复的工作
新的LTO又进行了如下改进,可以看到上面的lto.o文件被拆分了多个,避免了局部修改带来的开销
- 分析和内联函数不合并对象文件
- 提升编译速度
- 二次编译有链接器缓存,避免再次重新链接。如Xcode中的Module Cache
开启LTO优化
一般使用incremental增量式的LTO,优化会影响debug效率,最好不要在开发环境下启用
如果需要在debug环境下开启,则建议将Debug Information Level改成Line tables only
Code Size Improvements
指定LLVM/clang的优化级别
根据官方推荐,使用
-Os具有最大收益,代码执行效率的提升和可执行文件的体积最优
设置参数
SWIFT_OPTIMIZATION_LEVEL = "-O" GCC_OPTIMIZATION_LEVEL = s
sizecommand检测优化的结果
__TEXT具体包含的内容
更加详细的信息
组合优化
LLVM bitcode
- 它是一种特殊的中间代码,让应用支持
Bitcode,将多个arm架构发布到AppStore,当用户在下载ipa包的时候,appStore根据用户手机的具体arm架构将ipa的的bitcode转换成用户手机目标平台的机器码,减少内存。
- 编译过程
参考链接
https://devstreaming-cdn.apple.com/videos/wwdc/2019/409t7ah0xy3ocqab4a/409/409_whats_new_in_clang_and_llvm.pdf?dl=1
https://devstreaming-cdn.apple.com/videos/wwdc/2016/405i2ilotov3bazyei1/405/405_whats_new_in_llvm.pdf?dl=1
https://llvm.zcopy.site/
https://gclxry.com/visual-studio-profile-guided-optimization/
https://www.jianshu.com/p/1367dad95445
https://llvm.zcopy.site/post/61090.html
https://llvm.org/
https://llvm.org/docs/
clang命令速查表
OVERVIEW: clang LLVM compiler
USAGE: clang [options] file...
OPTIONS:
-### Print (but do not run) the commands to run for this compilation
--analyzer-output <value>
静态分析器报告输出格式 (html|plist|plist-multi-file|plist-html|text).
--analyze 运行静态分析仪
-arcmt-migrate-emit-errors 提交arc错误,尽管迁移可以解决错误
-arcmt-migrate-report-output <value> 报告输出
-B <dir> 将文件`dir`隐式的添加到搜索路径中,方便二进制查找
-CC 在预处理中包含内部宏的注释
-cfguard 发出windows控制流所需要的保护表
-cl-denorms-are-zero OpenCL only. Allow denormals to be flushed to zero.
-cl-fast-relaxed-math OpenCL only. Sets -cl-finite-math-only and -cl-unsafe-math-optimizations, and defines __FAST_RELAXED_MATH__.
-cl-finite-math-only OpenCL only. Allow floating-point optimizations that assume arguments and results are not NaNs or +-Inf.
-cl-fp32-correctly-rounded-divide-sqrt
OpenCL only. Specify that single precision floating-point divide and sqrt used in the program source are correctly rounded.
-cl-kernel-arg-info OpenCL only. Generate kernel argument metadata.
-cl-mad-enable OpenCL only. Allow use of less precise MAD computations in the generated binary.
-cl-no-signed-zeros OpenCL only. Allow use of less precise no signed zeros computations in the generated binary.
-cl-opt-disable OpenCL only. This option disables all optimizations. By default optimizations are enabled.
-cl-single-precision-constant
OpenCL only. Treat double precision floating-point constant as single precision constant.
-cl-std=<value> OpenCL language standard to compile for.
-cl-strict-aliasing OpenCL only. This option is added for compatibility with OpenCL 1.0.
-cl-uniform-work-group-size
OpenCL only. Defines that the global work-size be a multiple of the work-group size specified to clEnqueueNDRangeKernel
-cl-unsafe-math-optimizations
OpenCL only. Allow unsafe floating-point optimizations. Also implies -cl-no-signed-zeros and -cl-mad-enable.
--config <value> Specifies configuration file
--cuda-compile-host-device
Compile CUDA code for both host and device (default). Has no effect on non-CUDA compilations.
--cuda-device-only Compile CUDA code for device only
--cuda-gpu-arch=<value> CUDA GPU architecture (e.g. sm_35). May be specified more than once.
--cuda-host-only Compile CUDA code for host only. Has no effect on non-CUDA compilations.
--cuda-include-ptx=<value>
Include PTX for the following GPU architecture (e.g. sm_35) or 'all'. May be specified more than once.
--cuda-noopt-device-debug
Enable device-side debug info generation. Disables ptxas optimizations.
--cuda-path-ignore-env Ignore environment variables to detect CUDA installation
--cuda-path=<value> CUDA installation path
-cxx-isystem <directory>
向C++系统添加目录包括搜索路径
-C 在预处理输出中包含注释
-c 只运行预处理、编译和组装步骤
-dD 除正常输出外，以-E模式打印宏定义
-dependency-dot <value> 要写入点格式标头依赖项的文件名 -依赖文件<value>
-dI 除了正常输出外，在-E模式下打印include指令
-dM 以-E模式而不是正常输出打印宏定义
-D <macro>=<value> 定义宏变量
-emit-ast ***搜集输入源文件的语法分析树文****
-emit-llvm 对汇编程序和对象文件使用LLVM表示
-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang<value>
Trivial automatic variable initialization to zero is only here for benchmarks, it'll eventually be removed, and I'm OK with that because I'm only using it to benchmark
-E 只运行预处理器
-faddrsig 发出地址重要性表
-faligned-allocation 启用C++ 17对齐的分配函数
-fallow-editor-placeholders 将编辑器占位符视为有效源代码
-fansi-escape-codes 使用ANSI转义代码进行诊断
-fapinotes-cache-path=<directory> 不执行任何操作；API注释不再与模块分开缓存
-fapinotes-modules 启用基于模块的外部API notes支持
-fapinotes-swift-version=<version> 指定筛选API注释时要使用的Swift版本
-fapinotes 启用外部API notes支持
-fapple-kext 使用苹果的内核扩展ABI
-fapple-link-rtlib 强制链接clang builtins运行库
-fapple-pragma-pack 启用Apple gcc兼容的pragma包处理
-fapplication-extension 将代码限制为可用于应用程序扩展的代码
-fblocks 启用“块”语言功能
-fborland-extensions 接受Borland编译器支持的非标准构造
-fbuild-session-file=<file>
***使用<file>的最后修改时间作为构建会话时间戳 ***
-fbuild-session-timestamp=<time since Epoch in seconds>
当前生成会话开始的时间
-fbuiltin-module-map ***加载clang 内置的模块映射文件***
-fc++-static-destructors 启用C++静态析构函数注册（默认）
-fcall-saved-x10 Make the x10 register call-saved (AArch64 only)
-fcall-saved-x11 Make the x11 register call-saved (AArch64 only)
-fcall-saved-x12 Make the x12 register call-saved (AArch64 only)
-fcall-saved-x13 Make the x13 register call-saved (AArch64 only)
-fcall-saved-x14 Make the x14 register call-saved (AArch64 only)
-fcall-saved-x15 Make the x15 register call-saved (AArch64 only)
-fcall-saved-x18 Make the x18 register call-saved (AArch64 only)
-fcall-saved-x8 Make the x8 register call-saved (AArch64 only)
-fcall-saved-x9 Make the x9 register call-saved (AArch64 only)
-fcf-protection=<value> 控制流程结构保护。选项：return、branch、full、none。
-fcf-protection 允许 cf-protection 在 'full' 模式
-fchar8_t 允许 C++ 内置的类型 char8_t
-fclang-abi-compat=<version>
尝试匹配Clang<version>
-fcolor-diagnostics 在诊断中使用颜色
-fcomment-block-commands=<arg>
将<arg>中的每个逗号分隔参数视为文档注释块命令
-fcomplete-member-pointers
如果成员指针基类型在Microsoft ABI下是重要的，则要求它们是完整的
-fcoroutines-ts 启用对C++协同程序TS的支持
-fcoverage-mapping 生成覆盖率映射以启用代码覆盖率分析
-fcs-profile-generate=<directory>
生成插入指令的代码以将上下文相关的执行计数收集到<directory>/默认值.proflow（被LLVM_PROFILE_FILE env var覆盖）
-fcuda-approx-transcendentals
Use approximate transcendental functions
-fcuda-flush-denormals-to-zero
Flush denormal floating point values to zero in CUDA device mode.
-fcuda-short-ptr 使用32位指针访问常量/本地/共享地址空间。
-fcxx-exceptions 启用C++异常
-fdata-sections 将每个数据放入自己的部分（仅限ELF）
-fdebug-compilation-dir <value>
要嵌入调试信息中的编译目录。
-fdebug-info-for-profiling
发出额外的调试信息以使示例配置文件更准确。
-fdebug-macro 发出宏调试信息
-fdebug-prefix-map=<value>
在调试信息中重新映射文件源路径
-fdebug-ranges-base-address
在调试范围中使用DWARF基地址选择项
-fdebug-types-section 将调试类型放入它们自己的部分（仅限ELF）
-fdeclspec 允许declspec作为关键字
-fdelayed-template-parsing
解析翻译单元末尾的模板化函数定义
-fdelete-null-pointer-checks
将空指针的使用视为未定义的行为。
-fdiagnostics-absolute-paths
在诊断中打印绝对路径
-fdiagnostics-hotness-threshold=<number>
如果优化备注没有至少此配置文件计数，则阻止输出优化备注
-fdiagnostics-parseable-fixits
以机器可解析的形式打印修复它
-fdiagnostics-print-source-range-info
以数字形式打印源范围跨度
-fdiagnostics-show-hotness
Enable profile hotness information in diagnostic line
-fdiagnostics-show-note-include-stack
*** 显示诊断注释的包含堆栈 ***
-fdiagnostics-show-option
使用可映射诊断打印选项名称
-fdiagnostics-show-template-tree
打印不同模板的模板比较树
-fdigraphs 启用替代令牌表示 '<:', ':>', '<%', '%>', '%:', '%:%:' (default)
-fdiscard-value-names 丢弃LLVM-IR中的值名称
-fdollars-in-identifiers
Allow '$' in identifiers
-fdouble-square-bracket-attributes
Enable '[[]]' attributes in all C and C++ language modes
-fdwarf-exceptions Use DWARF style exceptions
-fembed-bitcode-marker 嵌入占位符LLVM IR数据作为标记
-fembed-bitcode=<option>
*** 嵌入LLVM位代码,(用于翻译不同平台目标代码）*** (option: off, all, bitcode, marker)
-fembed-bitcode 嵌入LLVM-IR位码作为数据
-femit-all-decls 提交所有声明，即使未使用
-fc-tls 使用emutls函数访问线程本地变量
-fenable-matrix Enable matrix data type and related builtin functions
-fexceptions 启用对异常处理的支持
-fexperimental-isel Enables the experimental global instruction selector
-fexperimental-new-pass-manager
Enables an experimental new pass manager in LLVM.
-ffast-math *** 允许激进的、有损的浮点优化 ***
-ffine-grained-bitfield-accesses
Use separate accesses for consecutive bitfield runs with legal widths and alignments.
-ffixed-point Enable fixed point types
-ffixed-r19 Reserve register r19 (Hexagon only)
-ffixed-r9 Reserve the r9 register (ARM only)
-ffixed-x10 Reserve the 10 register (AArch64 only)
-ffixed-x11 Reserve the 11 register (AArch64 only)
-ffixed-x12 Reserve the 12 register (AArch64 only)
-ffixed-x13 Reserve the 13 register (AArch64 only)
-ffixed-x14 Reserve the 14 register (AArch64 only)
-ffixed-x15 Reserve the 15 register (AArch64 only)
-ffixed-x18 Reserve the 18 register (AArch64 only)
-ffixed-x1 Reserve the 1 register (AArch64 only)
-ffixed-x20 Reserve the 20 register (AArch64 only)
-ffixed-x21 Reserve the 21 register (AArch64 only)
-ffixed-x22 Reserve the 22 register (AArch64 only)
-ffixed-x23 Reserve the 23 register (AArch64 only)
-ffixed-x24 Reserve the 24 register (AArch64 only)
-ffixed-x25 Reserve the 25 register (AArch64 only)
-ffixed-x26 Reserve the 26 register (AArch64 only)
-ffixed-x27 Reserve the 27 register (AArch64 only)
-ffixed-x28 Reserve the 28 register (AArch64 only)
-ffixed-x2 Reserve the 2 register (AArch64 only)
-ffixed-x3 Reserve the 3 register (AArch64 only)
-ffixed-x4 Reserve the 4 register (AArch64 only)
-ffixed-x5 Reserve the 5 register (AArch64 only)
-ffixed-x6 Reserve the 6 register (AArch64 only)
-ffixed-x7 Reserve the 7 register (AArch64 only)
-ffixed-x9 Reserve the 9 register (AArch64 only)
-fforce-emit-vtables 发出更多的虚拟表来改善去虚拟化
-fforce-enable-int128 允许int128_t类型
-ffp-contract=<value> Form fused FP ops (e.g. FMAs): fast (everywhere) | on (according to FP_CONTRACT pragma, default) | off (never fuse)
-ffreestanding 断言编译发生在独立环境中
-ffunction-sections 将每个函数放在自己的节中（仅限ELF）
-fgnu-keywords 不管语言标准如何，都允许GNU扩展关键字
-fgnu-runtime 生成与标准GNU Objective-C运行时兼容的输出
-fgnu89-inline ***使用gnu89内联语义***
-fgpu-rdc 生成可重定位设备代码，也称为独立编译模式。
-fimplicit-module-maps 隐式地在文件系统中搜索模块映射文件。
-finline-functions 内联适当函数
-finline-hint-functions 显式或隐式）标记为内联的内联函数
-finstrument-function-entry-bare 仅在内联后插入函数项，不带插入调用的参数
-finstrument-functions Generate calls to instrument function entry and exit
-fintegrated-as Enable the integrated assembler
-fkeep-static-consts Keep static const variables even if unused
-flto-jobs=<value> Controls the backend parallelism of -flto=thin (default of 0 means the number of threads will be derived from the number of CPUs detected)
-flto=<value> 将LTO模式设置为“full”或“thin”
-flto 在“完全”模式下启用LTO
-fmath-errno 需要数学函数通过设置errno来指示错误
-fmax-type-align=<value>
指定要对缺少显式对齐的指针强制执行的最大对齐方式
-fmerge-all-constants 允许合并常量
-fmodule-file=[<name>=]<file>
指定模块名到预编译模块文件的映射，或者在省略名称的情况下加载模块文件。
-fmodule-map-file=<file>
加载此模块映射文件***
-fmodule-name=<name> 指定要生成的模块的名称***
-fmodules-cache-path=<directory>
指定模块缓存路径***
-fmodules-decluse 要求声明模块中使用的模块 ***
-fmodules-disable-diagnostic-validation 加载模块时禁用诊断选项验证 ***
-fmodules-ignore-macro=<value> 生成和加载模块时忽略给定宏的定义 ***
-fmodules-prune-after=<seconds>
指定将认为模块文件未使用的间隔（以秒为单位） ***
-fmodules-prune-interval=<seconds>
指定尝试修剪模块缓存的间隔（秒） ***
-fmodules-search-all Search even non-imported modules to resolve references
-fmodules-strict-decluse
Like -fmodules-decluse 但要求所有头都在模块中 -fmodules-ts 启用对C++模块TS的支持
-fmodules-user-build-path <directory>
指定模块用户生成路径
-fmodules-validate-input-files-content
Validate PCM input files based on content if mtime differs
-fmodules-validate-once-per-build-session
如果模块在此生成会话期间已成功验证或加载，则不要验证模块的输入文件***
-fmodules-validate-system-headers
加载模块时验证模块所依赖的系统头 ***
-fmodules 启用“模块”语言功能 ***
-fms-compatibility-version=<value>
Dot-separated value representing the Microsoft compiler version number to report in _MSC_VER (0 = don't define it (default))
-fms-compatibility Enable full Microsoft Visual C++ compatibility
-fms-extensions 接受Microsoft编译器支持的一些非标准构造
-fmsc-version=<value> Microsoft compiler version number to report in _MSC_VER (0 = don't define it (default))
-fnew-alignment=<align> Specifies the largest alignment guaranteed by '::operator new(size_t)'
-fno-access-control 禁用C++访问控制 ***
-fno-addrsig 不发出地址重要性表 ***
-fno-apinotes-modules 禁用基于模块的外部API notes支持***
-fno-apinotes 禁用外部API注解支持
-fno-assume-sane-operator-new 不要假定C++的全局运算符new不能别名指针
-fno-autolink 禁用为自动库链接生成链接器指令
-fno-builtin-<value> 禁用特定函数的隐式内置知识
-fno-builtin 禁用函数的隐式内置知识
-fno-c++-static-destructors
Disable C++ static destructor registration
-fno-char8_t Disable C++ builtin type char8_t
-fno-common Compile common globals like normal definitions
-fno-complete-member-pointers
Do not require member pointer base types to be complete if they would be significant under the Microsoft ABI
-fno-constant-cfstrings 禁用创建CodeFoundation类型常量字符串 ****
-fno-constant-nsarray-literals
禁用从数组文本创建CodeFoundation类型常量初始值设定项“NSArray” ****
-fno-constant-nsdictionary-literals
禁用从字典文本创建CodeFoundation类型常量初始值设定项`NSDictionary`s
无法从数字文本创建CodeFoundation类型常量初始值设定项“NSNumber”
-fno-coverage-mapping 禁用代码覆盖率分析
-fno-crash-diagnostics 禁用自动生成预处理的源文件和脚本，以便在clang崩溃期间进行复制
-fno-debug-info-for-profiling
不要为示例探查器发出额外的调试信息。
-fno-debug-macro 不发出宏调试信息
-fno-declspec 不允许作为关键字
-fno-delayed-template-parsing
禁用延迟模板分析
-fno-delete-null-pointer-checks
不要将空指针的使用视为未定义的行为。
-fno-diagnostics-fixit-info
不包括诊断信息
-fno-digraphs 不允许替代令牌表示'<:', ':>', '<%', '%>', '%:', '%:%:'
-fno-discard-value-names 不要丢弃LLVM-IR中的值名
-fno-dollars-in-identifiers 在标识符中不允许使用“$”
-fno-double-square-bracket-attributes 在所有C和C++语言模式中禁用'[]]属性
-fno-elide-constructors 禁用C++复制构造器删除
-fno-elide-type Do not elide types when printing diagnostics
-fno-experimental-isel Disables the experimental global instruction selector
-fno-experimental-new-pass-manager
Disables an experimental new pass manager in LLVM.
-fno-fine-grained-bitfield-accesses
Use large-integer access for consecutive bitfield runs.
-fno-fixed-point Disable fixed point types
-fno-force-enable-int128
Disable support for int128_t type
-fno-gnu-inline-asm Disable GNU style inline asm
-fno-integrated-as Disable the integrated assembler
-fno-jump-tables Do not use jump tables for lowering switches
-fno-lax-vector-conversions
Disallow implicit conversions between vectors with a different number of elements or different element types
-fno-lto Disable LTO mode (default)
-fno-merge-all-constants
Disallow merging of constants
-fno-objc-infer-related-result-type
do not infer Objective-C related result type based on method family
-fno-operator-names Do not treat C++ operator name keywords as synonyms for operators
-fno-plt Do not use the PLT to make function calls
-fno-preserve-as-comments
Do not preserve comments in inline assembly
-fno-profile-generate Disable generation of profile instrumentation.
-fno-profile-instr-generate
Disable generation of profile instrumentation.
-fno-profile-instr-use Disable using instrumentation data for profile-guided optimization
-fno-register-global-dtors-with-atexit
Don't use atexit or __cxa_atexit to register global destructors
-fno-reroll-loops Turn off loop reroller
-fno-rtlib-add-rpath Do not add -rpath with architecture-specific resource directory to the linker flags
-fno-rtti-data Control emission of RTTI data
-fno-rtti Disable generation of rtti information
-fno-sanitize-address-poison-custom-array-cookie
Disable poisoning array cookies when using custom operator new[] in AddressSanitizer
-fno-sanitize-address-use-after-scope
在AddressSanitizer中禁用作用域检测后使用
-fno-sanitize-address-use-odr-indicator
Disable ODR indicator globals
-fno-sanitize-blacklist Don't use blacklist file for sanitizers
-fno-sanitize-cfi-cross-dso
Disable control flow integrity (CFI) checks for cross-DSO calls.
-fno-sanitize-coverage=<value>
Disable specified features of coverage instrumentation for Sanitizers
-fno-sanitize-memory-track-origins
Disable origins tracking in MemorySanitizer
-fno-sanitize-memory-use-after-dtor
Disable use-after-destroy detection in MemorySanitizer
-fno-sanitize-recover=<value>
Disable recovery for specified sanitizers
-fno-sanitize-stats Disable sanitizer statistics gathering.
-fno-sanitize-thread-atomics
Disable atomic operations instrumentation in ThreadSanitizer
-fno-sanitize-thread-func-entry-exit
Disable function entry/exit instrumentation in ThreadSanitizer
-fno-sanitize-thread-memory-access
Disable memory access instrumentation in ThreadSanitizer
-fno-sanitize-trap=<value>
Disable trapping for specified sanitizers
-fno-short-wchar Force wchar_t to be an unsigned int
-fno-show-column Do not include column number on diagnostics
-fno-show-source-location
Do not include source location information with diagnostics
-fno-signed-char Char is unsigned
-fno-signed-zeros Allow optimizations that ignore the sign of floating point zeros
-fno-spell-checking Disable spell-checking
-fno-stack-check Disable stack checking
-fno-stack-protector Disable the use of stack protectors
-fno-stack-size-section Don't emit section containing metadata on function stack sizes
-fno-standalone-debug Limit debug information produced to reduce size of debug binary
-fno-strict-float-cast-overflow
Relax language rules and try to match the behavior of the target's native float-to-int conversion instructions
-fno-temp-file Directly create compilation output files. This may lead to incorrect incremental builds if the compiler crashes
-fno-threadsafe-statics Do not emit code to make initialization of local statics thread safe
-fno-trigraphs Do not process trigraph sequences
-fno-unroll-loops Turn off loop unroller
-fno-use-cxa-atexit Don't use __cxa_atexit for calling destructors
-fno-use-init-array Don't use .init_array instead of .ctors
-fobjc-arc-exceptions Use EH-safe code when synthesizing retains and releases in -fobjc-arc
-fobjc-arc Synthesize retain and release calls for Objective-C pointers
-fobjc-exceptions Enable Objective-C exceptions
-fobjc-runtime=<value> Specify the target Objective-C runtime kind and version
-fobjc-weak Enable ARC-style weak references in Objective-C
-fopenmp-simd Emit OpenMP code only for SIMD-based constructs.
-fopenmp-targets=<value>
Specify comma-separated list of triples OpenMP offloading targets to be supported
-fopenmp Parse OpenMP pragmas and generate parallel code.
-foptimization-record-file=<file>
Specify the output name of the file containing the optimization remarks. Implies -fsave-optimization-record. On Darwin platforms, this cannot be used with multiple -arch <arch> options.
-foptimization-record-passes=<regex>
Only include passes which match a specified regular expression in the generated optimization record (by default, include all passes)
-forder-file-instrumentation
Generate instrumented code to collect order file into default.profraw file (overridden by '=' form of option or LLVM_PROFILE_FILE env var)
-fpack-struct=<value> Specify the default maximum struct packing alignment
-fpascal-strings Recognize and construct Pascal-style string literals
-fpass-plugin=<dsopath> Load pass plugin from a dynamic shared object file (only with new pass manager).
-fpcc-struct-return Override the default ABI to return all structs on the stack
-fpch-validate-input-files-content
Validate PCH input files based on content if mtime differs
-fplt Use the PLT to make function calls
-fplugin=<dsopath> Load the named plugin (dynamic shared object)
-fprebuilt-module-path=<directory>
Specify the prebuilt module path
-fprofile-exclude-files=<value>
Instrument only functions from files where names don't match all the regexes separated by a semi-colon
-fprofile-filter-files=<value>
Instrument only functions from files where names match any regex separated by a semi-colon
-fprofile-generate=<directory>
Generate instrumented code to collect execution counts into <directory>/default.profraw (overridden by LLVM_PROFILE_FILE env var)
-fprofile-generate Generate instrumented code to collect execution counts into default.profraw (overridden by LLVM_PROFILE_FILE env var)
-fprofile-instr-generate=<file>
Generate instrumented code to collect execution counts into <file> (overridden by LLVM_PROFILE_FILE env var)
-fprofile-instr-generate
Generate instrumented code to collect execution counts into default.profraw file (overridden by '=' form of option or LLVM_PROFILE_FILE env var)
-fprofile-instr-use=<value>
Use instrumentation data for profile-guided optimization
-fprofile-remapping-file=<file>
Use the remappings described in <file> to match the profile data against names in the program
-fprofile-sample-accurate
Specifies that the sample profile is accurate
-fprofile-sample-use=<value>
Enable sample-based profile guided optimizations
-fprofile-use=<pathname>
Use instrumentation data for profile-guided optimization. If pathname is a directory, it reads from <pathname>/default.profdata. Otherwise, it reads from file <pathname>.
-fptrauth-auth-traps Enable traps on authentication failures
-fptrauth-calls Enable signing and authentication of all indirect calls
-fptrauth-indirect-gotos
Enable signing and authentication of indirect goto targets
-fptrauth-intrinsics Enable pointer-authentication intrinsics
-fptrauth-returns Enable signing and authentication of return addresses
-fptrauth-soft Enable software lowering of pointer authentication
-freciprocal-math Allow division operations to be reassociated
-freg-struct-return Override the default ABI to return small structs in registers
-fregister-global-dtors-with-atexit
Use atexit or __cxa_atexit to register global destructors
-frelaxed-template-template-args
Enable C++17 relaxed template template argument matching
-freroll-loops Turn on loop reroller
-frtlib-add-rpath Add -rpath with architecture-specific resource directory to the linker flags
-fsanitize-address-field-padding=<value>
Level of field padding for AddressSanitizer
-fsanitize-address-globals-dead-stripping
Enable linker dead stripping of globals in AddressSanitizer
-fsanitize-address-poison-custom-array-cookie
Enable poisoning array cookies when using custom operator new[] in AddressSanitizer
-fsanitize-address-use-after-scope
Enable use-after-scope detection in AddressSanitizer
-fsanitize-address-use-odr-indicator
Enable ODR indicator globals to avoid false ODR violation reports in partially sanitized programs at the cost of an increase in binary size
-fsanitize-blacklist=<value>
Path to blacklist file for sanitizers
-fsanitize-cfi-cross-dso
Enable control flow integrity (CFI) checks for cross-DSO calls.
-fsanitize-cfi-icall-generalize-pointers
Generalize pointers in CFI indirect call type signature checks
-fsanitize-coverage=<value>
Specify the type of coverage instrumentation for Sanitizers
-fsanitize-hwaddress-abi=<value>
Select the HWAddressSanitizer ABI to target (interceptor or platform, default interceptor)
-fsanitize-memory-track-origins=<value>
Enable origins tracking in MemorySanitizer
-fsanitize-memory-track-origins
Enable origins tracking in MemorySanitizer
-fsanitize-memory-use-after-dtor
Enable use-after-destroy detection in MemorySanitizer
-fsanitize-recover=<value>
Enable recovery for specified sanitizers
-fsanitize-stats Enable sanitizer statistics gathering.
-fsanitize-system-blacklist=<value>
Path to system blacklist file for sanitizers
-fsanitize-thread-atomics
Enable atomic operations instrumentation in ThreadSanitizer (default)
-fsanitize-thread-func-entry-exit
Enable function entry/exit instrumentation in ThreadSanitizer (default)
-fsanitize-thread-memory-access
Enable memory access instrumentation in ThreadSanitizer (default)
-fsanitize-trap=<value> Enable trapping for specified sanitizers
-fsanitize-undefined-strip-path-components=<number>
Strip (or keep only, if negative) a given number of path components when emitting check metadata.
-fsanitize=<check> Turn on runtime checks for various forms of undefined or suspicious behavior. See user manual for available checks
-fsave-optimization-record=<format>
Generate an optimization record file in a specific format
-fsave-optimization-record
Generate a YAML optimization record file
-fseh-exceptions Use SEH style exceptions
-fshort-enums Allocate to an enum type only as many bytes as it needs for the declared range of possible values
-fshort-wchar Force wchar_t to be a short unsigned int
-fshow-overloads=<value>
Which overload candidates to show when overload resolution fails: best|all; defaults to all
-fsized-deallocation Enable C++14 sized global deallocation functions
-fsjlj-exceptions Use SjLj style exceptions
-fslp-vectorize Enable the superword-level parallelism vectorization passes
-fsplit-dwarf-inlining Provide minimal debug info in the object/executable to facilitate online symbolication/stack traces in the absence of .dwo/.dwp files when using Split DWARF
-fsplit-lto-unit Enables splitting of the LTO unit.
-fstack-check Enable stack checking
-fstack-protector-all Enable stack protectors for all functions
-fstack-protector-strong
Enable stack protectors for some functions vulnerable to stack smashing. Compared to -fstack-protector, this uses a stronger heuristic that includes functions containing arrays of any size (and any type), as well as any calls to alloca or the taking of an address from a local variable
-fstack-protector Enable stack protectors for some functions vulnerable to stack smashing. This uses a loose heuristic which considers functions vulnerable if they contain a char (or 8bit integer) array or constant sized calls to alloca, which are of greater size than ssp-buffer-size (default: 8 bytes). All variable sized calls to alloca are considered vulnerable
-fstack-size-section Emit section containing metadata on function stack sizes
-fstandalone-debug Emit full debug info for all types used by the program
-fstrict-enums Enable optimizations based on the strict definition of an enum's value range
-fstrict-float-cast-overflow
Assume that overflowing float-to-int casts are undefined (default)
-fstrict-return Always treat control flow paths that fall off the end of a non-void function as unreachable
-fstrict-vtable-pointers
Enable optimizations based on the strict rules for overwriting polymorphic C++ objects
-ftarget-variant-availability-checks
Enable availability checks for the target variant platform
-fthinlto-index=<value> Perform ThinLTO importing using provided function summary index
-ftrap-function=<value> Issue call to specified function rather than a trap instruction
-ftrapv-handler=<function name>
Specify the function to be called on overflow
-ftrapv Trap on integer overflow
-ftrigraphs Process trigraph sequences
-ftrivial-auto-var-init=<value>
Initialize trivial automatic stack variables: uninitialized (default) | pattern
-funique-section-names Use unique names for text and data sections (ELF Only)
-funroll-loops Turn on loop unroller
-fuse-init-array Use .init_array instead of .ctors
-fvalidate-ast-input-files-content
Compute and store the hash of input files used to build an AST. Files with mismatching mtime's are considered valid if both contents is identical
-fveclib=<value> Use the given vector functions library
-fvectorize Enable the loop vectorization passes
-fvisibility-global-new-delete-hidden
Give global C++ operator new and delete declarations hidden visibility
-fvisibility-inlines-hidden
Give inline C++ member functions hidden visibility by default
-fvisibility-ms-compat Give global types 'default' visibility and global functions and variables 'hidden' visibility by default
-fvisibility=<value> Set the default symbol visibility for all global declarations
-fwhole-program-vtables Enables whole-program vtable optimization. Requires -flto
-fwrapv Treat signed integer overflow as two's complement
-fwritable-strings Store string literals as writable data
-fxray-always-emit-customevents
Determine whether to always emit __xray_customevent(...) calls even if the function it appears in is not always instrumented.
-fxray-always-emit-typedevents
Determine whether to always emit __xray_typedevent(...) calls even if the function it appears in is not always instrumented.
-fxray-always-instrument= <value>
DEPRECATED: Filename defining the whitelist for imbuing the 'always instrument' XRay attribute.
-fxray-attr-list= <value>
Filename defining the list of functions/types for imbuing XRay attributes.
-fxray-instruction-threshold= <value>
Sets the minimum function size to instrument with XRay
-fxray-instrumentation-bundle= <value>
Select which XRay instrumentation points to emit. Options: all, none, function, custom. Default is 'all'.
-fxray-instrument Generate XRay instrumentation sleds on function entry and exit
-fxray-link-deps Tells clang to add the link dependencies for XRay.
-fxray-modes= <value> List of modes to link in by default into XRay instrumented binaries.
-fxray-never-instrument= <value>
DEPRECATED: Filename defining the whitelist for imbuing the 'never instrument' XRay attribute.
-fzvector Enable System z vector language extension
-F <value> Add directory to framework include search path
--gcc-toolchain=<value> Use the gcc toolchain at the given directory
-gcodeview-ghash Emit type record hashes in a .debug$H section
-gcodeview Generate CodeView debug information
-gdwarf-2 Generate source-level debug information with dwarf version 2
-gdwarf-3 Generate source-level debug information with dwarf version 3
-gdwarf-4 Generate source-level debug information with dwarf version 4
-gdwarf-5 Generate source-level debug information with dwarf version 5
-gembed-source Embed source text in DWARF debug sections
-gline-directives-only Emit debug line info directives only
-gline-tables-only Emit debug line number tables only
-gmodules Generate debug info with external references to clang modules or precompiled headers
-gno-embed-source Restore the default behavior of not embedding source text in DWARF debug sections
-gsplit-dwarf=<value> Set DWARF fission mode to either 'split' or 'single'
-gz=<value> DWARF debug sections compression type
-gz DWARF debug sections compression type
-G <size> Put objects of at most <size> bytes into small data section (MIPS / Hexagon)
-g Generate source-level debug information
--help-hidden Display help for hidden options
-help Display available options
--hip-device-lib-path=<value>
HIP device library path
--hip-device-lib=<value>
HIP device library
--hip-link Link clang-offload-bundler bundles for HIP
-H Show header includes and nesting depth
-I- Restrict all prior -I flags to double-quoted inclusion and remove current directory from include path
-iapinotes-modules <directory>
Add directory to the API notes search path referenced by module name
-idirafter <value> Add directory to AFTER include search path
-iframeworkwithsysroot <directory>
Add directory to SYSTEM framework search path, absolute paths are relative to -isysroot
-iframework <value> Add directory to SYSTEM framework search path
-imacros <file> Include macros from file before parsing
-include-pch <file> Include precompiled header file
-include <file> Include file before parsing
-index-header-map Make the next included directory (-I or -F) an indexer header map
-index-ignore-system-symbols
Ignore symbols from system headers
-index-record-codegen-name
Record the codegen name for symbols
-index-store-path <value>
Enable indexing with the specified data store path
-iprefix <dir> Set the -iwithprefix/-iwithprefixbefore prefix
-iquote <directory> Add directory to QUOTE include search path
-isysroot <dir> Set the system root directory (usually /)
-isystem-after <directory>
Add directory to end of the SYSTEM include search path
-isystem <directory> Add directory to SYSTEM include search path
-ivfsoverlay <value> Overlay the virtual filesystem described by file over the real file system
-iwithprefixbefore <dir>
Set directory to include search path with prefix
-iwithprefix <dir> Set directory to SYSTEM include search path with prefix
-iwithsysroot <directory>
Add directory to SYSTEM include search path, absolute paths are relative to -isysroot
-I <dir> Add directory to include search path
--libomptarget-nvptx-path=<value>
Path to libomptarget-nvptx libraries
-L <dir> Add directory to library search path
-mabicalls Enable SVR4-style position-independent code (Mips only)
-malign-double Align doubles to two words in structs (x86 only)
-mbackchain Link stack frames through backchain on System Z
-mbranch-protection=<value>
Enforce targets of indirect branches and function returns
-mcmse Allow use of CMSE (Armv8-M Security Extensions)
-mcode-object-v3 Enable code object v3 (AMDGPU only)
-mcrc Allow use of CRC instructions (ARM/Mips only)
-mcumode CU wavefront execution mode is used (AMDGPU only)
-MD Write a depfile containing user and system headers
-meabi <value> Set EABI type, e.g. 4, 5 or gnu (default depends on triple)
-membedded-data Place constants in the .rodata section instead of the .sdata section even if they meet the -G <size> threshold (MIPS)
-mexecute-only Disallow generation of data access to code sections (ARM only)
-mextern-sdata Assume that externally defined data is in the small data if it meets the -G <size> threshold (MIPS)
-mfentry Insert calls to fentry at function entry (x86 only)
-mfix-cortex-a53-835769 Workaround Cortex-A53 erratum 835769 (AArch64 only)
-mfp32 Use 32-bit floating point registers (MIPS only)
-mfp64 Use 64-bit floating point registers (MIPS only)
-MF <file> Write depfile output from -MMD, -MD, -MM, or -M to <file>
-mgeneral-regs-only Generate code which only uses the general purpose registers (AArch64 only)
-mglobal-merge Enable merging of globals
-mgpopt Use GP relative accesses for symbols known to be in a small data section (MIPS)
-MG Add missing headers to depfile
-mhvx-length=<value> Set Hexagon Vector Length
-mhvx=<value> Enable Hexagon Vector eXtensions
-mhvx Enable Hexagon Vector eXtensions
-miamcu Use Intel MCU ABI
--migrate Run the migrator
-mincremental-linker-compatible
(integrated-as) Emit an object file which can be used with an incremental linker
-mindirect-jump=<value> Change indirect jump instructions to inhibit speculation
-mios-version-min=<value>
Set iOS deployment target
-MJ <value> Write a compilation database entry per input
-mllvm <value> Additional arguments to forward to LLVM's option processing
-mlocal-sdata Extend the -G behaviour to object local data (MIPS)
-mlong-calls Generate branches with extended addressability, usually via indirect jumps.
-mmacosx-version-min=<value>
Set Mac OS X deployment target
-mmadd4 Enable the generation of 4-operand madd.s, madd.d and related instructions.
-MMD Write a depfile containing user headers
-mmemops Enable generation of memop instructions
-mms-bitfields Set the default structure layout to be compatible with the Microsoft compiler standard
-mmsa Enable MSA ASE (MIPS only)
-mmt Enable MT ASE (MIPS only)
-MM Like -MMD, but also implies -E and writes to stdout by default
-mno-abicalls Disable SVR4-style position-independent code (Mips only)
-mno-code-object-v3 Disable code object v3 (AMDGPU only)
-mno-crc Disallow use of CRC instructions (Mips only)
-mno-cumode WGP wavefront execution mode is used (AMDGPU only)
-mno-embedded-data Do not place constants in the .rodata section instead of the .sdata if they meet the -G <size> threshold (MIPS)
-mno-execute-only Allow generation of data access to code sections (ARM only)
-mno-extern-sdata Do not assume that externally defined data is in the small data if it meets the -G <size> threshold (MIPS)
-mno-fix-cortex-a53-835769
Don't workaround Cortex-A53 erratum 835769 (AArch64 only)
-mno-global-merge Disable merging of globals
-mno-gpopt Do not use GP relative accesses for symbols known to be in a small data section (MIPS)
-mno-hvx Disable Hexagon Vector eXtensions
-mno-implicit-float Don't generate implicit floating point instructions
-mno-incremental-linker-compatible
(integrated-as) Emit an object file which cannot be used with an incremental linker
-mno-local-sdata Do not extend the -G behaviour to object local data (MIPS)
-mno-long-calls Restore the default behaviour of not generating long calls
-mno-madd4 Disable the generation of 4-operand madd.s, madd.d and related instructions.
-mno-memops Disable generation of memop instructions
-mno-movt Disallow use of movt/movw pairs (ARM only)
-mno-ms-bitfields Do not set the default structure layout to be compatible with the Microsoft compiler standard
-mno-msa Disable MSA ASE (MIPS only)
-mno-mt Disable MT ASE (MIPS only)
-mno-neg-immediates Disallow converting instructions with negative immediates to their negation or inversion.
-mno-nvj Disable generation of new-value jumps
-mno-nvs Disable generation of new-value stores
-mno-outline Disable function outlining (AArch64 only)
-mno-packets Disable generation of instruction packets
-mno-relax Disable linker relaxation
-mno-restrict-it Allow generation of deprecated IT blocks for ARMv8. It is off by default for ARMv8 Thumb mode
-mno-sram-ecc Disable SRAM ECC (AMDGPU only)
-mno-stack-arg-probe Disable stack probes which are enabled by default
-mno-tls-direct-seg-refs
Disable direct TLS access through segment registers
-mno-unaligned-access Force all memory accesses to be aligned (AArch32/AArch64 only)
-mno-wavefrontsize64 Wavefront size 32 is used
-mno-xnack Disable XNACK (AMDGPU only)
-mnocrc Disallow use of CRC instructions (ARM only)
-mnvj Enable generation of new-value jumps
-mnvs Enable generation of new-value stores
-module-dependency-dir <value>
Directory to dump module dependencies to
-module-file-info Provide information about a particular module file
-momit-leaf-frame-pointer
Omit frame pointer setup for leaf functions
-moutline Enable function outlining (AArch64 only)
-mpackets Enable generation of instruction packets
-mpie-copy-relocations Use copy relocations support for PIE builds
-mprefer-vector-width=<value>
Specifies preferred vector width for auto-vectorization. Defaults to 'none' which allows target specific decisions.
-MP Create phony target for each dependency (other than main file)
-mqdsp6-compat Enable hexagon-qdsp6 backward compatibility
-MQ <value> Specify name of main file output to quote in depfile
-mrelax-all (integrated-as) Relax all machine instructions
-mrelax Enable linker relaxation
-mrestrict-it Disallow generation of deprecated IT blocks for ARMv8. It is on by default for ARMv8 Thumb mode.
-mrtd Make StdCall calling convention the default
-msign-return-address=<value>
Select return address signing scope
-msoft-float Use software floating point
-msram-ecc Enable SRAM ECC (AMDGPU only)
-mstack-alignment=<value>
Set the stack alignment
-mstack-arg-probe Enable stack probes
-mstack-probe-size=<value>
Set the stack probe size
-mstackrealign Force realign the stack at entry to every function
-mthread-model <value> The thread model to use, e.g. posix, single (posix by default)
-mtls-direct-seg-refs Enable direct TLS access through segment registers (default)
-mtp=<value> Thread pointer access method (AArch32/AArch64 only)
-MT <value> Specify name of main file output in depfile
-munaligned-access Allow memory accesses to be unaligned (AArch32/AArch64 only)
-MV Use NMake/Jom format for the depfile
-mwavefrontsize64 Wavefront size 64 is used
-mxnack Enable XNACK (AMDGPU only)
-M Like -MD, but also implies -E and writes to stdout by default
--no-cuda-gpu-arch=<value>
Remove GPU architecture (e.g. sm_35) from the list of GPUs to compile for. 'all' resets the list to its default value.
--no-cuda-include-ptx=<value>
Do not include PTX for the following GPU architecture (e.g. sm_35) or 'all'. May be specified more than once.
--no-cuda-version-check Don't error out if the detected version of the CUDA install is too low for the requested CUDA gpu architecture.
--no-system-header-prefix=<prefix>
Treat all #include paths starting with <prefix> as not including a system header.
-nobuiltininc Disable builtin #include directories
-nostdinc++ Disable standard #include directories for the C++ standard library
-ObjC++ Treat source input files as Objective-C++ inputs
-objcmt-atomic-property Make migration to 'atomic' properties
-objcmt-migrate-all Enable migration to modern ObjC
-objcmt-migrate-annotation
Enable migration to property and method annotations
-objcmt-migrate-designated-init
Enable migration to infer NS_DESIGNATED_INITIALIZER for initializer methods
-objcmt-migrate-instancetype
Enable migration to infer instancetype for method result type
-objcmt-migrate-literals
Enable migration to modern ObjC literals
-objcmt-migrate-ns-macros
Enable migration to NS_ENUM/NS_OPTIONS macros
-objcmt-migrate-property-dot-syntax
Enable migration of setter/getter messages to property-dot syntax
-objcmt-migrate-property
Enable migration to modern ObjC property
-objcmt-migrate-protocol-conformance
Enable migration to add protocol conformance on classes
-objcmt-migrate-readonly-property
Enable migration to modern ObjC readonly property
-objcmt-migrate-readwrite-property
Enable migration to modern ObjC readwrite property
-objcmt-migrate-subscripting
Enable migration to modern ObjC subscripting
-objcmt-ns-nonatomic-iosonly
Enable migration to use NS_NONATOMIC_IOSONLY macro for setting property's 'atomic' attribute
-objcmt-returns-innerpointer-property
Enable migration to annotate property with NS_RETURNS_INNER_POINTER
-objcmt-whitelist-dir-path=<value>
Only modify files with a filename contained in the provided directory path
-ObjC Treat source input files as Objective-C inputs
-o <file> Write output to <file>
-pg Enable mcount instrumentation
-pipe Use pipes between commands, when possible
--precompile Only precompile the input
-print-effective-triple Print the effective target triple
-print-file-name=<file> Print the full library path of <file>
-print-ivar-layout Enable Objective-C Ivar layout bitmap print trace
-print-libgcc-file-name Print the library path for the currently used compiler runtime library ("libgcc.a" or "libclang_rt.builtins.*.a")
-print-prog-name=<name> Print the full program path of <name>
-print-resource-dir Print the resource directory pathname
-print-search-dirs Print the paths used for finding libraries and programs
-print-supported-cpus Print supported cpu models for the given target (if target is not specified, it will print the supported cpus for the default target)
-print-target-triple Print the normalized target triple
-pthread Support POSIX threads in generated code
--ptxas-path=<value> Path to ptxas (used for compiling CUDA code)
-P Disable linemarker output in -E mode
-Qn Do not emit metadata containing compiler name and version
-Qunused-arguments Don't emit warning for unused driver arguments
-Qy Emit metadata containing compiler name and version
-relocatable-pch Whether to build a relocatable precompiled header
-rewrite-legacy-objc Rewrite Legacy Objective-C source to C++
-rewrite-objc Rewrite Objective-C source to C++
-Rpass-analysis=<value> Report transformation analysis from optimization passes whose name matches the given POSIX regular expression
-Rpass-missed=<value> Report missed transformations by optimization passes whose name matches the given POSIX regular expression
-Rpass=<value> Report transformations performed by optimization passes whose name matches the given POSIX regular expression
-rtlib=<value> Compiler runtime library to use
-R<remark> Enable the specified remark
-save-stats=<value> Save llvm statistics.
-save-stats Save llvm statistics.
-save-temps=<value> Save intermediate compilation results.
-save-temps Save intermediate compilation results
-serialize-diagnostics <value>
Serialize compiler diagnostics to a file
-shared-libsan Dynamically link the sanitizer runtime
-static-libsan Statically link the sanitizer runtime
-std=<value> Language standard to compile for
-stdlib=<value> C++ standard library to use
--system-header-prefix=<prefix>
Treat all #include paths starting with <prefix> as including a system header.
-S Only run preprocess and compilation steps
-target-variant <value> Generate code that may run on a particular variant of the deployment target
--target=<value> Generate code for the given target
-Tbss <addr> Set starting address of BSS to <addr>
-Tdata <addr> Set starting address of DATA to <addr>
-time Time individual commands
-traditional-cpp Enable some traditional CPP emulation
-trigraphs Process trigraph sequences
-Ttext <addr> Set starting address of TEXT to <addr>
-T <script> Specify <script> as linker script
-undef undef all system defines
-unwindlib=<value> Unwind library to use
-U <macro> Undefine macro <macro>
--verify-debug-info Verify the binary representation of debug output
-verify-pch Load and verify that a pre-compiled header file is not stale
--version Print version information
-v Show commands to run and use verbose output
-Wa,<arg> Pass the comma separated arguments in <arg> to the assembler
-Wdeprecated Enable warnings for deprecated constructs and define __DEPRECATED
-Wl,<arg> Pass the comma separated arguments in <arg> to the linker
-working-directory <value>
Resolve file paths relative to the specified directory
-Wp,<arg> Pass the comma separated arguments in <arg> to the preprocessor
-W<warning> Enable the specified warning
-w Suppress all warnings
-Xanalyzer <arg> Pass <arg> to the static analyzer
-Xassembler <arg> Pass <arg> to the assembler
-Xclang <arg> Pass <arg> to the clang compiler
-Xcuda-fatbinary <arg> Pass <arg> to fatbinary invocation
-Xcuda-ptxas <arg> Pass <arg> to the ptxas assembler
-Xlinker <arg> Pass <arg> to the linker
-Xopenmp-target=<triple> <arg>
Pass <arg> to the target offloading toolchain identified by <triple>.
-Xopenmp-target <arg> Pass <arg> to the target offloading toolchain.
-Xpreprocessor <arg> Pass <arg> to the preprocessor
-x <language> Treat subsequent input files as having type <language>
-z <arg> Pass -z <arg> to the linker
