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-rw-r--r--doc/optimization.txt13
1 files changed, 9 insertions, 4 deletions
diff --git a/doc/optimization.txt b/doc/optimization.txt
index b3dca645a8..1a0b98cd0e 100644
--- a/doc/optimization.txt
+++ b/doc/optimization.txt
@@ -17,15 +17,15 @@ Understanding these overoptimized functions:
As many functions tend to be a bit difficult to understand because
of optimizations, it can be hard to optimize them further, or write
architecture-specific versions. It is recommended to look at older
-revisions of the interesting files (web frontends for the various Libav
-branches are listed at http://libav.org/download.html).
+revisions of the interesting files (web frontends for the various FFmpeg
+branches are listed at http://ffmpeg.org/download.html).
Alternatively, look into the other architecture-specific versions in
the x86/, ppc/, alpha/ subdirectories. Even if you don't exactly
comprehend the instructions, it could help understanding the functions
and how they can be optimized.
NOTE: If you still don't understand some function, ask at our mailing list!!!
-(https://lists.libav.org/mailman/listinfo/libav-devel)
+(http://lists.ffmpeg.org/mailman/listinfo/ffmpeg-devel)
When is an optimization justified?
@@ -191,11 +191,16 @@ __asm__() block.
Use external asm (nasm/yasm) or inline asm (__asm__()), do not use intrinsics.
The latter requires a good optimizing compiler which gcc is not.
+When debugging a x86 external asm compilation issue, if lost in the macro
+expansions, add DBG=1 to your make command-line: the input file will be
+preprocessed, stripped of the debug/empty lines, then compiled, showing the
+actual lines causing issues.
+
Inline asm vs. external asm
---------------------------
Both inline asm (__asm__("..") in a .c file, handled by a compiler such as gcc)
and external asm (.s or .asm files, handled by an assembler such as yasm/nasm)
-are accepted in Libav. Which one to use differs per specific case.
+are accepted in FFmpeg. Which one to use differs per specific case.
- if your code is intended to be inlined in a C function, inline asm is always
better, because external asm cannot be inlined