ipriyanshi1708 created this revision. Herald added a project: All. ipriyanshi1708 added reviewers: samtebbs, aaron.ballman. ipriyanshi1708 published this revision for review. Herald added a project: clang.
Fixes https://github.com/llvm/llvm-project/issues/53681 . Optimization flags are not documented in the Clang documentation. So I have added information about Optimization flags in the documentation. Repository: rG LLVM Github Monorepo https://reviews.llvm.org/D147141 Files: clang/docs/UsersManual.rst Index: clang/docs/UsersManual.rst =================================================================== --- clang/docs/UsersManual.rst +++ clang/docs/UsersManual.rst @@ -2199,6 +2199,41 @@ link-time optimizations like whole program inter-procedural basic block reordering. +Optimization Flags +------------------ + +The optimization flags control the level of optimization that the compiler performs on the code. For example, ``-O1`` enables a set of optimizations that are designed to improve code performance while still maintaining debugging capabilities. ``-Og`` enables optimizations that do not interfere with debugging, while ``-Ofast`` enables more aggressive optimizations that may sacrifice some debugging capabilities in exchange for maximum performance. + +You can use these optimization flags with the Clang compiler by specifying them on the command line when invoking the compiler. For example, to compile a C++ source file with the ``-O2`` optimization level, you would run the following command: + + .. code-block:: console + + $ clang++ -O2 myfile.cpp -o myfile + +Here are some common optimization flags with basic descriptions for different versions of the Clang compiler: + +Clang 3.8 and earlier: +"""""""""""""""""""""" + +1. ``-O0``: no optimization +2. ``-O1``: basic optimization, such as function inlining and constant propagation +3. ``-O2``: more aggressive optimization, such as loop unrolling and instruction scheduling +4. ``-O3``: even more aggressive optimization, such as loop vectorization and function cloning +5. ``-Os``: optimize for code size rather than execution speed +6. ``-Ofast``: enable all optimizations that do not violate strict standards compliance + +Clang 3.9 and later: +"""""""""""""""""""" + +1. ``-O0``: no optimization +2. ``-O1``: basic optimization, such as function inlining and constant propagation +3. ``-O2``: more aggressive optimization, such as loop unrolling and instruction scheduling +4. ``-O3``: even more aggressive optimization, such as loop vectorization and function cloning +5. ``-Os``: optimize for code size rather than execution speed +6. ``-Ofast``: enable all optimizations that do not violate strict standards compliance +7. ``-Oz``: like -Os, but with more aggressive optimization for code size +8. ``-Og``: optimize for debuggability, with minimal optimization that does not interfere with debugging + Profile Guided Optimization ---------------------------
Index: clang/docs/UsersManual.rst =================================================================== --- clang/docs/UsersManual.rst +++ clang/docs/UsersManual.rst @@ -2199,6 +2199,41 @@ link-time optimizations like whole program inter-procedural basic block reordering. +Optimization Flags +------------------ + +The optimization flags control the level of optimization that the compiler performs on the code. For example, ``-O1`` enables a set of optimizations that are designed to improve code performance while still maintaining debugging capabilities. ``-Og`` enables optimizations that do not interfere with debugging, while ``-Ofast`` enables more aggressive optimizations that may sacrifice some debugging capabilities in exchange for maximum performance. + +You can use these optimization flags with the Clang compiler by specifying them on the command line when invoking the compiler. For example, to compile a C++ source file with the ``-O2`` optimization level, you would run the following command: + + .. code-block:: console + + $ clang++ -O2 myfile.cpp -o myfile + +Here are some common optimization flags with basic descriptions for different versions of the Clang compiler: + +Clang 3.8 and earlier: +"""""""""""""""""""""" + +1. ``-O0``: no optimization +2. ``-O1``: basic optimization, such as function inlining and constant propagation +3. ``-O2``: more aggressive optimization, such as loop unrolling and instruction scheduling +4. ``-O3``: even more aggressive optimization, such as loop vectorization and function cloning +5. ``-Os``: optimize for code size rather than execution speed +6. ``-Ofast``: enable all optimizations that do not violate strict standards compliance + +Clang 3.9 and later: +"""""""""""""""""""" + +1. ``-O0``: no optimization +2. ``-O1``: basic optimization, such as function inlining and constant propagation +3. ``-O2``: more aggressive optimization, such as loop unrolling and instruction scheduling +4. ``-O3``: even more aggressive optimization, such as loop vectorization and function cloning +5. ``-Os``: optimize for code size rather than execution speed +6. ``-Ofast``: enable all optimizations that do not violate strict standards compliance +7. ``-Oz``: like -Os, but with more aggressive optimization for code size +8. ``-Og``: optimize for debuggability, with minimal optimization that does not interfere with debugging + Profile Guided Optimization ---------------------------
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