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@@ -1,6 +1,8 @@
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optimization Tips (for libavcodec):
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+===================================
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What to optimize:
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+-----------------
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If you plan to do non-x86 architecture specific optimizations (SIMD normally),
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then take a look in the i386/ directory, as most important functions are
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already optimized for MMX.
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@@ -9,7 +11,9 @@ If you want to do x86 optimizations then you can either try to finetune the
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stuff in the i386 directory or find some other functions in the C source to
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optimize, but there aren't many left.
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+
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Understanding these overoptimized functions:
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+--------------------------------------------
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As many functions tend to be a bit difficult to understand because
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of optimizations, it can be hard to optimize them further, or write
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architecture-specific versions. It is recommened to look at older
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@@ -23,7 +27,9 @@ and how they can be optimized.
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NOTE: If you still don't understand some function, ask at our mailing list!!!
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(http://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel)
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+
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What speedup justifies an optimizetion?
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+---------------------------------------
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Normaly with clean&simple optimizations and widely used codecs a overall
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speedup of the affected codec of 0.1% is enough. These speedups accumulate
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and can make a big difference after a while ...
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@@ -35,6 +41,7 @@ small and readable than to make it 1% faster.
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WTF is that function good for ....:
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+-----------------------------------
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The primary purpose of that list is to avoid wasting time to optimize functions
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which are rarely used
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@@ -145,9 +152,11 @@ The minimum guaranteed alignment is written in the .h files, for example:
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Links:
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+======
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http://www.aggregate.org/MAGIC/
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x86-specific:
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+-------------
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http://developer.intel.com/design/pentium4/manuals/248966.htm
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The IA-32 Intel Architecture Software Developer's Manual, Volume 2:
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@@ -161,7 +170,7 @@ http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/22007.pd
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ARM-specific:
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-
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+-------------
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ARM Architecture Reference Manual (up to ARMv5TE):
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http://www.arm.com/community/university/eulaarmarm.html
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@@ -176,7 +185,7 @@ Optimization guide for Intel XScale (used in Sharp Zaurus PDA):
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http://download.intel.com/design/intelxscale/27347302.pdf
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PowerPC-specific:
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-
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+-----------------
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PowerPC32/AltiVec PIM:
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www.freescale.com/files/32bit/doc/ref_manual/ALTIVECPEM.pdf
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@@ -188,6 +197,7 @@ http://www-01.ibm.com/chips/techlib/techlib.nsf/techdocs/30B3520C93F437AB8725706
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http://www-01.ibm.com/chips/techlib/techlib.nsf/techdocs/9F820A5FFA3ECE8C8725716A0062585F/$file/CBE_Handbook_v1.1_24APR2007_pub.pdf
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SPARC-specific:
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+---------------
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SPARC Joint Programming Specification (JPS1): Commonality
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http://www.fujitsu.com/downloads/PRMPWR/JPS1-R1.0.4-Common-pub.pdf
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@@ -198,6 +208,7 @@ VIS Whitepaper (contains optimization guidelines)
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http://www.sun.com/processors/vis/download/vis/vis_whitepaper.pdf
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GCC asm links:
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+--------------
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official doc but quite ugly
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http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
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Michael Niedermayer