runtime: improve memmove performance on arm64

runtime: improve memmove performance on arm64

Replace the memmove implementation for moves of 17 bytes or larger
with an implementation from ARM optimized software. The moves of 16
bytes or fewer are unchanged, but the registers used are updated to
match the rest of the implementation.

This implementation makes use of new optimizations:
 - software pipelined loop for large (>128 byte) moves
 - medium size moves (17..128 bytes) have a new implementation
 - address realignment when src or dst is unaligned
 - preference for aligned src (loads) or dst (stores) depending on CPU

To support preference for aligned loads or aligned stores, a new CPU
flag is added. This flag indicates that the detected micro
architecture performs better with aligned loads. Some tested CPUs did
not exhibit a significant difference and are left with the default
behavior of realigning based on the destination address (stores).

Neoverse N1 (Tested on Graviton 2)
name                               old time/op    new time/op     delta
Memmove/0-4                          1.88ns ± 1%     1.87ns ± 1%   -0.58%  (p=0.020 n=10+10)
Memmove/1-4                          4.40ns ± 0%     4.40ns ± 0%     ~     (all equal)
Memmove/8-4                          3.88ns ± 3%     3.80ns ± 0%   -1.97%  (p=0.001 n=10+9)
Memmove/16-4                         3.90ns ± 3%     3.80ns ± 0%   -2.49%  (p=0.000 n=10+9)
Memmove/32-4                         4.80ns ± 0%     4.40ns ± 0%   -8.33%  (p=0.000 n=9+8)
Memmove/64-4                         5.86ns ± 0%     5.00ns ± 0%  -14.76%  (p=0.000 n=8+8)
Memmove/128-4                        8.46ns ± 0%     8.06ns ± 0%   -4.62%  (p=0.000 n=10+10)
Memmove/256-4                        12.4ns ± 0%     12.2ns ± 0%   -1.61%  (p=0.000 n=10+10)
Memmove/512-4                        19.5ns ± 0%     19.1ns ± 0%   -2.05%  (p=0.000 n=10+10)
Memmove/1024-4                       33.7ns ± 0%     33.5ns ± 0%   -0.59%  (p=0.000 n=10+10)
Memmove/2048-4                       62.1ns ± 0%     59.0ns ± 0%   -4.99%  (p=0.000 n=10+10)
Memmove/4096-4                        117ns ± 1%      110ns ± 0%   -5.66%  (p=0.000 n=10+10)
MemmoveUnalignedDst/64-4             6.41ns ± 0%     5.62ns ± 0%  -12.32%  (p=0.000 n=10+7)
MemmoveUnalignedDst/128-4            9.40ns ± 0%     8.34ns ± 0%  -11.24%  (p=0.000 n=10+10)
MemmoveUnalignedDst/256-4            12.8ns ± 0%     12.8ns ± 0%     ~     (all equal)
MemmoveUnalignedDst/512-4            20.4ns ± 0%     19.7ns ± 0%   -3.43%  (p=0.000 n=9+10)
MemmoveUnalignedDst/1024-4           34.1ns ± 0%     35.1ns ± 0%   +2.93%  (p=0.000 n=9+9)
MemmoveUnalignedDst/2048-4           61.5ns ± 0%     60.4ns ± 0%   -1.77%  (p=0.000 n=10+10)
MemmoveUnalignedDst/4096-4            122ns ± 0%      113ns ± 0%   -7.38%  (p=0.002 n=8+10)
MemmoveUnalignedSrc/64-4             7.25ns ± 1%     6.26ns ± 0%  -13.64%  (p=0.000 n=9+9)
MemmoveUnalignedSrc/128-4            10.5ns ± 0%      9.7ns ± 0%   -7.52%  (p=0.000 n=10+10)
MemmoveUnalignedSrc/256-4            17.1ns ± 0%     17.3ns ± 0%   +1.17%  (p=0.000 n=10+10)
MemmoveUnalignedSrc/512-4            27.0ns ± 0%     27.0ns ± 0%     ~     (all equal)
MemmoveUnalignedSrc/1024-4           46.7ns ± 0%     35.7ns ± 0%  -23.55%  (p=0.000 n=10+9)
MemmoveUnalignedSrc/2048-4           85.2ns ± 0%     61.2ns ± 0%  -28.17%  (p=0.000 n=10+8)
MemmoveUnalignedSrc/4096-4            162ns ± 0%      113ns ± 0%  -30.25%  (p=0.000 n=10+10)

name                               old speed      new speed       delta
Memmove/4096-4                     35.2GB/s ± 0%   37.1GB/s ± 0%   +5.56%  (p=0.000 n=10+9)
MemmoveUnalignedSrc/1024-4         21.9GB/s ± 0%   28.7GB/s ± 0%  +30.90%  (p=0.000 n=10+10)
MemmoveUnalignedSrc/2048-4         24.0GB/s ± 0%   33.5GB/s ± 0%  +39.18%  (p=0.000 n=10+9)
MemmoveUnalignedSrc/4096-4         25.3GB/s ± 0%   36.2GB/s ± 0%  +43.50%  (p=0.000 n=10+7)

Cortex-A72 (Graviton 1)
name                               old time/op    new time/op    delta
Memmove/0-4                          3.06ns ± 3%    3.08ns ± 1%     ~     (p=0.958 n=10+9)
Memmove/1-4                          8.72ns ± 0%    7.85ns ± 0%   -9.98%  (p=0.002 n=8+10)
Memmove/8-4                          8.29ns ± 0%    8.29ns ± 0%     ~     (all equal)
Memmove/16-4                         8.29ns ± 0%    8.29ns ± 0%     ~     (all equal)
Memmove/32-4                         8.19ns ± 2%    8.29ns ± 0%     ~     (p=0.114 n=10+10)
Memmove/64-4                         18.3ns ± 4%    10.0ns ± 0%  -45.36%  (p=0.000 n=10+10)
Memmove/128-4                        14.8ns ± 0%    17.4ns ± 0%  +17.77%  (p=0.000 n=10+10)
Memmove/256-4                        21.8ns ± 0%    23.1ns ± 0%   +5.96%  (p=0.000 n=10+10)
Memmove/512-4                        35.8ns ± 0%    37.2ns ± 0%   +3.91%  (p=0.000 n=10+10)
Memmove/1024-4                       63.7ns ± 0%    67.2ns ± 0%   +5.49%  (p=0.000 n=10+10)
Memmove/2048-4                        126ns ± 0%     123ns ± 0%   -2.38%  (p=0.000 n=10+10)
Memmove/4096-4                        238ns ± 1%     243ns ± 1%   +1.93%  (p=0.000 n=10+10)
MemmoveUnalignedDst/64-4             19.3ns ± 1%    12.0ns ± 1%  -37.49%  (p=0.000 n=10+10)
MemmoveUnalignedDst/128-4            17.2ns ± 0%    17.4ns ± 0%   +1.16%  (p=0.000 n=10+10)
MemmoveUnalignedDst/256-4            28.2ns ± 8%    29.2ns ± 0%     ~     (p=0.352 n=10+10)
MemmoveUnalignedDst/512-4            49.8ns ± 3%    48.9ns ± 0%     ~     (p=1.000 n=10+10)
MemmoveUnalignedDst/1024-4           89.5ns ± 0%    80.5ns ± 1%  -10.02%  (p=0.000 n=10+10)
MemmoveUnalignedDst/2048-4            180ns ± 0%     127ns ± 0%  -29.44%  (p=0.000 n=9+10)
MemmoveUnalignedDst/4096-4            347ns ± 0%     244ns ± 0%  -29.59%  (p=0.000 n=10+9)
MemmoveUnalignedSrc/128-4            16.1ns ± 0%    21.8ns ± 0%  +35.40%  (p=0.000 n=10+10)
MemmoveUnalignedSrc/256-4            24.9ns ± 8%    26.6ns ± 0%   +6.70%  (p=0.015 n=10+10)
MemmoveUnalignedSrc/512-4            39.4ns ± 6%    40.6ns ± 0%     ~     (p=0.352 n=10+10)
MemmoveUnalignedSrc/1024-4           72.5ns ± 0%    83.0ns ± 1%  +14.44%  (p=0.000 n=9+10)
MemmoveUnalignedSrc/2048-4            129ns ± 1%     128ns ± 1%     ~     (p=0.179 n=10+10)
MemmoveUnalignedSrc/4096-4            241ns ± 0%     253ns ± 1%   +4.99%  (p=0.000 n=9+9)

Cortex-A53 (Raspberry Pi 3)
name                               old time/op    new time/op    delta
Memmove/0-4                          11.0ns ± 0%    11.0ns ± 1%     ~     (p=0.294 n=8+10)
Memmove/1-4                          29.6ns ± 0%    28.0ns ± 1%   -5.41%  (p=0.000 n=9+10)
Memmove/8-4                          23.5ns ± 0%    22.1ns ± 0%   -6.11%  (p=0.000 n=8+8)
Memmove/16-4                         23.7ns ± 1%    22.1ns ± 0%   -6.59%  (p=0.000 n=10+8)
Memmove/32-4                         27.9ns ± 0%    27.1ns ± 0%   -3.13%  (p=0.000 n=8+8)
Memmove/64-4                         33.8ns ± 0%    31.5ns ± 1%   -6.99%  (p=0.000 n=8+10)
Memmove/128-4                        45.6ns ± 0%    44.2ns ± 1%   -3.23%  (p=0.000 n=9+10)
Memmove/256-4                        69.3ns ± 0%    69.3ns ± 0%     ~     (p=0.072 n=8+8)
Memmove/512-4                         127ns ± 0%     110ns ± 0%  -13.39%  (p=0.000 n=8+8)
Memmove/1024-4                        222ns ± 0%     205ns ± 1%   -7.66%  (p=0.000 n=7+10)
Memmove/2048-4                        411ns ± 0%     366ns ± 0%  -10.98%  (p=0.000 n=8+9)
Memmove/4096-4                        795ns ± 1%     695ns ± 1%  -12.63%  (p=0.000 n=10+10)
MemmoveUnalignedDst/64-4             44.0ns ± 0%    40.5ns ± 0%   -7.93%  (p=0.000 n=8+8)
MemmoveUnalignedDst/128-4            59.6ns ± 0%    54.9ns ± 0%   -7.85%  (p=0.000 n=9+9)
MemmoveUnalignedDst/256-4            98.2ns ±11%    90.0ns ± 1%     ~     (p=0.130 n=10+10)
MemmoveUnalignedDst/512-4             161ns ± 2%     145ns ± 1%   -9.96%  (p=0.000 n=10+10)
MemmoveUnalignedDst/1024-4            281ns ± 0%     265ns ± 0%   -5.65%  (p=0.000 n=9+8)
MemmoveUnalignedDst/2048-4            528ns ± 0%     482ns ± 0%   -8.73%  (p=0.000 n=8+9)
MemmoveUnalignedDst/4096-4           1.02µs ± 1%    0.92µs ± 0%  -10.00%  (p=0.000 n=10+8)
MemmoveUnalignedSrc/64-4             42.4ns ± 1%    40.5ns ± 0%   -4.39%  (p=0.000 n=10+8)
MemmoveUnalignedSrc/128-4            57.4ns ± 0%    57.0ns ± 1%   -0.75%  (p=0.048 n=9+10)
MemmoveUnalignedSrc/256-4            88.1ns ± 1%    89.6ns ± 0%   +1.70%  (p=0.000 n=9+8)
MemmoveUnalignedSrc/512-4             160ns ± 2%     144ns ± 0%   -9.89%  (p=0.000 n=10+8)
MemmoveUnalignedSrc/1024-4            286ns ± 0%     266ns ± 1%   -6.69%  (p=0.000 n=8+10)
MemmoveUnalignedSrc/2048-4            525ns ± 0%     483ns ± 1%   -7.96%  (p=0.000 n=9+10)
MemmoveUnalignedSrc/4096-4           1.01µs ± 0%    0.92µs ± 1%   -9.40%  (p=0.000 n=8+10)

Change-Id: Ia1144e9d4dfafdece6e167c5e576bf80f254c8ab
Reviewed-on: https://go-review.googlesource.com/c/go/+/243357
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>
Reviewed-by: eric fang <eric.fang@arm.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>