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Wilco Dijkstra c86063bdc0 Optimized memcmp
This is an optimized memcmp for AArch64.  This is a complete rewrite
using a different algorithm.  The previous version split into cases
where both inputs were aligned, the inputs were mutually aligned and
unaligned using a byte loop.  The new version combines all these cases,
while small inputs of less than 8 bytes are handled separately.

This allows the main code to be sped up using unaligned loads since
there are now at least 8 bytes to be compared.  After the first 8 bytes,
align the first input.  This ensures each iteration does at most one
unaligned access and mutually aligned inputs behave as aligned.
After the main loop, process the last 8 bytes using unaligned accesses.

This improves performance of (mutually) aligned cases by 25% and
unaligned by >500% (yes >6 times faster) on large inputs.

ChangeLog:
2017-06-28  Wilco Dijkstra  <wdijkstr@arm.com>

        * newlib/libc/machine/aarch64/memcmp.S (memcmp):
        Rewrite of optimized memcmp.

GLIBC benchtests/bench-memcmp.c performance comparison for Cortex-A53:

Length    1, alignment  1/ 1:		153%
Length    1, alignment  1/ 1:		119%
Length    1, alignment  1/ 1:		154%
Length    2, alignment  2/ 2:		121%
Length    2, alignment  2/ 2:		140%
Length    2, alignment  2/ 2:		121%
Length    3, alignment  3/ 3:		105%
Length    3, alignment  3/ 3:		105%
Length    3, alignment  3/ 3:		105%
Length    4, alignment  4/ 4:		155%
Length    4, alignment  4/ 4:		154%
Length    4, alignment  4/ 4:		161%
Length    5, alignment  5/ 5:		173%
Length    5, alignment  5/ 5:		173%
Length    5, alignment  5/ 5:		173%
Length    6, alignment  6/ 6:		145%
Length    6, alignment  6/ 6:		145%
Length    6, alignment  6/ 6:		145%
Length    7, alignment  7/ 7:		125%
Length    7, alignment  7/ 7:		125%
Length    7, alignment  7/ 7:		125%
Length    8, alignment  8/ 8:		111%
Length    8, alignment  8/ 8:		130%
Length    8, alignment  8/ 8:		124%
Length    9, alignment  9/ 9:		160%
Length    9, alignment  9/ 9:		160%
Length    9, alignment  9/ 9:		150%
Length   10, alignment 10/10:		170%
Length   10, alignment 10/10:		137%
Length   10, alignment 10/10:		150%
Length   11, alignment 11/11:		160%
Length   11, alignment 11/11:		160%
Length   11, alignment 11/11:		160%
Length   12, alignment 12/12:		146%
Length   12, alignment 12/12:		168%
Length   12, alignment 12/12:		156%
Length   13, alignment 13/13:		167%
Length   13, alignment 13/13:		167%
Length   13, alignment 13/13:		173%
Length   14, alignment 14/14:		167%
Length   14, alignment 14/14:		168%
Length   14, alignment 14/14:		168%
Length   15, alignment 15/15:		168%
Length   15, alignment 15/15:		173%
Length   15, alignment 15/15:		173%
Length    1, alignment  0/ 0:		134%
Length    1, alignment  0/ 0:		127%
Length    1, alignment  0/ 0:		119%
Length    2, alignment  0/ 0:		94%
Length    2, alignment  0/ 0:		94%
Length    2, alignment  0/ 0:		106%
Length    3, alignment  0/ 0:		82%
Length    3, alignment  0/ 0:		87%
Length    3, alignment  0/ 0:		82%
Length    4, alignment  0/ 0:		115%
Length    4, alignment  0/ 0:		115%
Length    4, alignment  0/ 0:		122%
Length    5, alignment  0/ 0:		127%
Length    5, alignment  0/ 0:		119%
Length    5, alignment  0/ 0:		127%
Length    6, alignment  0/ 0:		103%
Length    6, alignment  0/ 0:		100%
Length    6, alignment  0/ 0:		100%
Length    7, alignment  0/ 0:		82%
Length    7, alignment  0/ 0:		91%
Length    7, alignment  0/ 0:		87%
Length    8, alignment  0/ 0:		111%
Length    8, alignment  0/ 0:		124%
Length    8, alignment  0/ 0:		124%
Length    9, alignment  0/ 0:		136%
Length    9, alignment  0/ 0:		136%
Length    9, alignment  0/ 0:		136%
Length   10, alignment  0/ 0:		136%
Length   10, alignment  0/ 0:		135%
Length   10, alignment  0/ 0:		136%
Length   11, alignment  0/ 0:		136%
Length   11, alignment  0/ 0:		136%
Length   11, alignment  0/ 0:		135%
Length   12, alignment  0/ 0:		136%
Length   12, alignment  0/ 0:		136%
Length   12, alignment  0/ 0:		136%
Length   13, alignment  0/ 0:		135%
Length   13, alignment  0/ 0:		136%
Length   13, alignment  0/ 0:		136%
Length   14, alignment  0/ 0:		136%
Length   14, alignment  0/ 0:		136%
Length   14, alignment  0/ 0:		136%
Length   15, alignment  0/ 0:		136%
Length   15, alignment  0/ 0:		136%
Length   15, alignment  0/ 0:		136%
Length    4, alignment  0/ 0:		115%
Length    4, alignment  0/ 0:		115%
Length    4, alignment  0/ 0:		115%
Length   32, alignment  0/ 0:		127%
Length   32, alignment  7/ 2:		395%
Length   32, alignment  0/ 0:		127%
Length   32, alignment  0/ 0:		127%
Length    8, alignment  0/ 0:		111%
Length    8, alignment  0/ 0:		124%
Length    8, alignment  0/ 0:		124%
Length   64, alignment  0/ 0:		128%
Length   64, alignment  6/ 4:		475%
Length   64, alignment  0/ 0:		131%
Length   64, alignment  0/ 0:		134%
Length   16, alignment  0/ 0:		128%
Length   16, alignment  0/ 0:		119%
Length   16, alignment  0/ 0:		128%
Length  128, alignment  0/ 0:		129%
Length  128, alignment  5/ 6:		475%
Length  128, alignment  0/ 0:		130%
Length  128, alignment  0/ 0:		129%
Length   32, alignment  0/ 0:		126%
Length   32, alignment  0/ 0:		126%
Length   32, alignment  0/ 0:		126%
Length  256, alignment  0/ 0:		127%
Length  256, alignment  4/ 8:		545%
Length  256, alignment  0/ 0:		126%
Length  256, alignment  0/ 0:		128%
Length   64, alignment  0/ 0:		171%
Length   64, alignment  0/ 0:		171%
Length   64, alignment  0/ 0:		174%
Length  512, alignment  0/ 0:		126%
Length  512, alignment  3/10:		585%
Length  512, alignment  0/ 0:		126%
Length  512, alignment  0/ 0:		127%
Length  128, alignment  0/ 0:		129%
Length  128, alignment  0/ 0:		128%
Length  128, alignment  0/ 0:		129%
Length 1024, alignment  0/ 0:		125%
Length 1024, alignment  2/12:		611%
Length 1024, alignment  0/ 0:		126%
Length 1024, alignment  0/ 0:		126%
Length  256, alignment  0/ 0:		128%
Length  256, alignment  0/ 0:		127%
Length  256, alignment  0/ 0:		128%
Length 2048, alignment  0/ 0:		125%
Length 2048, alignment  1/14:		625%
Length 2048, alignment  0/ 0:		125%
Length 2048, alignment  0/ 0:		125%
Length  512, alignment  0/ 0:		126%
Length  512, alignment  0/ 0:		127%
Length  512, alignment  0/ 0:		127%
Length 4096, alignment  0/ 0:		125%
Length 4096, alignment  0/16:		125%
Length 4096, alignment  0/ 0:		125%
Length 4096, alignment  0/ 0:		125%
Length 1024, alignment  0/ 0:		126%
Length 1024, alignment  0/ 0:		126%
Length 1024, alignment  0/ 0:		126%
Length 8192, alignment  0/ 0:		125%
Length 8192, alignment 63/18:		636%
Length 8192, alignment  0/ 0:		125%
Length 8192, alignment  0/ 0:		125%
Length   16, alignment  1/ 2:		317%
Length   16, alignment  1/ 2:		317%
Length   16, alignment  1/ 2:		317%
Length   32, alignment  2/ 4:		395%
Length   32, alignment  2/ 4:		395%
Length   32, alignment  2/ 4:		398%
Length   64, alignment  3/ 6:		475%
Length   64, alignment  3/ 6:		475%
Length   64, alignment  3/ 6:		477%
Length  128, alignment  4/ 8:		479%
Length  128, alignment  4/ 8:		479%
Length  128, alignment  4/ 8:		479%
Length  256, alignment  5/10:		543%
Length  256, alignment  5/10:		539%
Length  256, alignment  5/10:		543%
Length  512, alignment  6/12:		585%
Length  512, alignment  6/12:		585%
Length  512, alignment  6/12:		585%
Length 1024, alignment  7/14:		611%
Length 1024, alignment  7/14:		611%
Length 1024, alignment  7/14:		611%
2017-06-29 20:36:35 +02:00
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newlib Optimized memcmp 2017-06-29 20:36:35 +02:00
texinfo * texinfo/texinfo.tex: Update to version 2009-03-28.05. 2009-04-21 12:36:46 +00:00
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