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author | Anton Khirnov <anton@khirnov.net> | 2022-11-14 17:55:40 +0100 |
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committer | Anton Khirnov <anton@khirnov.net> | 2023-03-20 10:52:17 +0100 |
commit | a36ad2c649c5da5e09d6f4491c5b9e18194e7289 (patch) | |
tree | 228cb1d425c6ed725888754da1faee4d16767de7 /doc | |
parent | 27f8c9b27bce42a4a6a4c64e03fab769579c8683 (diff) | |
download | ffmpeg-a36ad2c649c5da5e09d6f4491c5b9e18194e7289.tar.gz |
doc/developer.texi: document the use of other languages than C
Diffstat (limited to 'doc')
-rw-r--r-- | doc/developer.texi | 38 |
1 files changed, 36 insertions, 2 deletions
diff --git a/doc/developer.texi b/doc/developer.texi index 1275fa4f84..db5afafa4b 100644 --- a/doc/developer.texi +++ b/doc/developer.texi @@ -56,9 +56,9 @@ and should try to fix issues their commit causes. @anchor{Coding Rules} @chapter Coding Rules -@section C language features +@section Language -FFmpeg is programmed in the ISO C99 language, extended with: +FFmpeg is mainly programmed in the ISO C99 language, extended with: @itemize @bullet @item Atomic operations from C11 @file{stdatomic.h}. They are emulated on @@ -83,6 +83,40 @@ complex numbers; mixed statements and declarations. @end itemize +@subsection SIMD/DSP +@anchor{SIMD/DSP} + +As modern compilers are unable to generate efficient SIMD or other +performance-critical DSP code from plain C, handwritten assembly is used. +Usually such code is isolated in a separate function. Then the standard approach +is writing multiple versions of this function – a plain C one that works +everywhere and may also be useful for debugging, and potentially multiple +architecture-specific optimized implementations. Initialization code then +chooses the best available version at runtime and loads it into a function +pointer; the function in question is then always called through this pointer. + +The specific syntax used for writing assembly is: +@itemize @bullet +@item +NASM on x86; + +@item +GAS on ARM. +@end itemize + +@subsection Other languages + +Other languages than C may be used in special cases: +@itemize @bullet +@item +Compiler intrinsics or inline assembly when the code in question cannot be +written in the standard way described in the @ref{SIMD/DSP} section. This +typically applies to code that needs to be inlined. + +@item +Objective-C where required for interacting with macOS-specific interfaces. +@end itemize + @section Code formatting conventions There are the following guidelines regarding the indentation in files: |