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| -rw-r--r-- | Doc/c-api/intro.rst | 19 | ||||
| -rw-r--r-- | Include/pyport.h | 22 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/C API/2021-09-16-18-05-20.bpo-45116.WxXewl.rst | 3 |
3 files changed, 44 insertions, 0 deletions
diff --git a/Doc/c-api/intro.rst b/Doc/c-api/intro.rst index 83824bb..aac28b1 100644 --- a/Doc/c-api/intro.rst +++ b/Doc/c-api/intro.rst @@ -111,6 +111,25 @@ complete listing. .. versionadded:: 3.3 +.. c:macro:: Py_ALWAYS_INLINE + + Ask the compiler to always inline a static inline function. The compiler can + ignore it and decides to not inline the function. + + It can be used to inline performance critical static inline functions when + building Python in debug mode with function inlining disabled. For example, + MSC disables function inlining when building in debug mode. + + Marking blindly a static inline function with Py_ALWAYS_INLINE can result in + worse performances (due to increased code size for example). The compiler is + usually smarter than the developer for the cost/benefit analysis. + + It must be specified before the function return type. Usage:: + + static inline Py_ALWAYS_INLINE int random(void) { return 4; } + + .. versionadded:: 3.11 + .. c:macro:: Py_CHARMASK(c) Argument must be a character or an integer in the range [-128, 127] or [0, diff --git a/Include/pyport.h b/Include/pyport.h index 0aaa4ee..af7fbe7 100644 --- a/Include/pyport.h +++ b/Include/pyport.h @@ -557,6 +557,28 @@ extern "C" { #define _Py_HOT_FUNCTION #endif +// Ask the compiler to always inline a static inline function. The compiler can +// ignore it and decides to not inline the function. +// +// It can be used to inline performance critical static inline functions when +// building Python in debug mode with function inlining disabled. For example, +// MSC disables function inlining when building in debug mode. +// +// Marking blindly a static inline function with Py_ALWAYS_INLINE can result in +// worse performances (due to increased code size for example). The compiler is +// usually smarter than the developer for the cost/benefit analysis. +// +// It must be specified before the function return type. Usage: +// +// static inline Py_ALWAYS_INLINE int random(void) { return 4; } +#if defined(__GNUC__) || defined(__clang__) || defined(__INTEL_COMPILER) +# define Py_ALWAYS_INLINE __attribute__((always_inline)) +#elif defined(_MSC_VER) +# define Py_ALWAYS_INLINE __forceinline +#else +# define Py_ALWAYS_INLINE +#endif + // Py_NO_INLINE // Disable inlining on a function. For example, it reduces the C stack // consumption: useful on LTO+PGO builds which heavily inline code (see diff --git a/Misc/NEWS.d/next/C API/2021-09-16-18-05-20.bpo-45116.WxXewl.rst b/Misc/NEWS.d/next/C API/2021-09-16-18-05-20.bpo-45116.WxXewl.rst new file mode 100644 index 0000000..cf3db5c --- /dev/null +++ b/Misc/NEWS.d/next/C API/2021-09-16-18-05-20.bpo-45116.WxXewl.rst @@ -0,0 +1,3 @@ +Add the :c:macro:`Py_ALWAYS_INLINE` macro to ask the compiler to always +inline a static inline function. The compiler can ignore it and decides to +not inline the function. Patch by Victor Stinner. |