| 1 | This is a patched version of zlib modified to use
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| 2 | Pentium-optimized assembly code in the deflation algorithm. The files
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| 3 | changed/added by this patch are:
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| 4 |
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| 5 | README.586
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| 6 | match.S
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| 7 |
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| 8 | The effectiveness of these modifications is a bit marginal, as the the
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| 9 | program's bottleneck seems to be mostly L1-cache contention, for which
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| 10 | there is no real way to work around without rewriting the basic
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| 11 | algorithm. The speedup on average is around 5-10% (which is generally
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| 12 | less than the amount of variance between subsequent executions).
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| 13 | However, when used at level 9 compression, the cache contention can
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| 14 | drop enough for the assembly version to achieve 10-20% speedup (and
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| 15 | sometimes more, depending on the amount of overall redundancy in the
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| 16 | files). Even here, though, cache contention can still be the limiting
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| 17 | factor, depending on the nature of the program using the zlib library.
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| 18 | This may also mean that better improvements will be seen on a Pentium
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| 19 | with MMX, which suffers much less from L1-cache contention, but I have
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| 20 | not yet verified this.
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| 21 |
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| 22 | Note that this code has been tailored for the Pentium in particular,
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| 23 | and will not perform well on the Pentium Pro (due to the use of a
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| 24 | partial register in the inner loop).
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| 25 |
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| 26 | If you are using an assembler other than GNU as, you will have to
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| 27 | translate match.S to use your assembler's syntax. (Have fun.)
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| 28 |
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| 29 | Brian Raiter
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| 30 | breadbox@muppetlabs.com
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| 31 | April, 1998
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| 32 |
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| 33 |
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| 34 | Added for zlib 1.1.3:
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| 35 |
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| 36 | The patches come from
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| 37 | http://www.muppetlabs.com/~breadbox/software/assembly.html
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| 38 |
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| 39 | To compile zlib with this asm file, copy match.S to the zlib directory
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| 40 | then do:
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| 41 |
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| 42 | CFLAGS="-O3 -DASMV" ./configure
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| 43 | make OBJA=match.o
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