doc: Check standalone compilation before submitting new components.

[ffmpeg] / doc / optimization.txt

diff --git a/doc/optimization.txt b/doc/optimization.txt
index 3a5d85e62a1dc278991a72af4ee749ce48111a95..78e0077e3054653c888b2bcf91042fd8fde5d9b2 100644 (file)
--- 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 (for a web frontend try ViewVC at
-http://svn.ffmpeg.org/ffmpeg/trunk/).
+revisions of the interesting files (web frontends for the various Libav
+branches are listed at http://libav.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!!!
-(http://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel)
+(https://lists.libav.org/mailman/listinfo/libav-devel)
 
 
 When is an optimization justified?
@@ -172,6 +172,12 @@ yasm), you do this by using:
 cglobal functon_name, num_args, num_regs, num_xmm_regs
 In inline asm, you specify clobbered registers at the end of your asm:
 __asm__(".." ::: "%eax").
+If gcc is not set to support sse (-msse) it will not accept xmm registers
+in the clobber list. For that we use two macros to declare the clobbers.
+XMM_CLOBBERS should be used when there are other clobbers, for example:
+__asm__(".." ::: XMM_CLOBBERS("xmm0",) "eax");
+and XMM_CLOBBERS_ONLY should be used when the only clobbers are xmm registers:
+__asm__(".." :: XMM_CLOBBERS_ONLY("xmm0"));
 
 Do not expect a compiler to maintain values in your registers between separate
 (inline) asm code blocks. It is not required to. For example, this is bad:
@@ -195,7 +201,7 @@ 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 FFmpeg. Which one to use differs per specific case.
+are accepted in Libav. 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