[FFmpeg-cvslog] doc/developer.texi: document the use of other languages than C

[Anton Khirnov]

ffmpeg | branch: master | Anton Khirnov <anton at khirnov.net> | Mon Nov 14 17:55:40 2022 +0100| [a36ad2c649c5da5e09d6f4491c5b9e18194e7289] | committer: Anton Khirnov

doc/developer.texi: document the use of other languages than C

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=a36ad2c649c5da5e09d6f4491c5b9e18194e7289
---

 doc/developer.texi | 38 ++++++++++++++++++++++++++++++++++++--
 1 file 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
 
- at section C language features
+ at 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
 
+ at subsection SIMD/DSP
+ at 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:
+ at itemize @bullet
+ at item
+NASM on x86;
+
+ at item
+GAS on ARM.
+ at end itemize
+
+ at subsection Other languages
+
+Other languages than C may be used in special cases:
+ at itemize @bullet
+ at 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.
+
+ at item
+Objective-C where required for interacting with macOS-specific interfaces.
+ at end itemize
+
 @section Code formatting conventions
 
 There are the following guidelines regarding the indentation in files: