internal/bytealg: add assembly implementation of Compare/CompareString on mips64x

internal/bytealg: add assembly implementation of Compare/CompareString on mips64x

name                         old time/op    new time/op    delta
BytesCompare/1                 28.9ns ± 4%    22.8ns ± 0%    -21.23%  (p=0.000 n=9+10)
BytesCompare/2                 34.6ns ± 0%    23.5ns ± 0%    -32.01%  (p=0.000 n=8+10)
BytesCompare/4                 54.6ns ± 0%    41.4ns ± 0%    -24.18%  (p=0.001 n=8+9)
BytesCompare/8                 73.9ns ± 0%    49.7ns ± 0%    -32.75%  (p=0.002 n=8+10)
BytesCompare/16                 113ns ± 0%      23ns ± 0%    -79.56%  (p=0.000 n=9+10)
BytesCompare/32                 190ns ± 0%      26ns ± 0%    -86.53%  (p=0.000 n=10+10)
BytesCompare/64                 345ns ± 0%      44ns ± 0%    -87.19%  (p=0.000 n=10+10)
BytesCompare/128                654ns ± 0%      52ns ± 0%    -91.97%  (p=0.000 n=9+8)
BytesCompare/256               1.27µs ± 0%    0.08µs ± 1%    -94.10%  (p=0.000 n=8+10)
BytesCompare/512               2.51µs ± 0%    0.12µs ± 0%    -95.26%  (p=0.000 n=9+9)
BytesCompare/1024              4.99µs ± 0%    0.21µs ± 1%    -95.84%  (p=0.000 n=8+10)
BytesCompare/2048              9.94µs ± 0%    0.38µs ± 0%    -96.13%  (p=0.000 n=8+10)
CompareBytesEqual               105ns ± 0%      64ns ± 0%    -39.05%  (p=0.000 n=10+9)
CompareBytesToNil              34.8ns ± 1%    39.5ns ± 3%    +13.48%  (p=0.000 n=10+10)
CompareBytesEmpty              33.6ns ± 3%    36.6ns ± 0%     +8.77%  (p=0.000 n=10+10)
CompareBytesIdentical          29.7ns ± 0%    36.6ns ± 0%    +23.23%  (p=0.000 n=10+10)
CompareBytesSameLength         69.1ns ± 0%    51.1ns ± 0%    -26.05%  (p=0.000 n=10+10)
CompareBytesDifferentLength    69.8ns ± 0%    51.1ns ± 0%    -26.79%  (p=0.000 n=10+10)
CompareBytesBigUnaligned       5.15ms ± 0%    2.18ms ± 0%    -57.62%  (p=0.000 n=9+9)
CompareBytesBig                5.28ms ± 0%    0.28ms ± 0%    -94.64%  (p=0.000 n=8+10)
CompareBytesBigIdentical       29.7ns ± 0%    36.8ns ± 0%    +23.91%  (p=0.000 n=8+8)

name                         old speed      new speed      delta
CompareBytesBigUnaligned      204MB/s ± 0%   480MB/s ± 0%   +135.94%  (p=0.000 n=9+9)
CompareBytesBig               198MB/s ± 0%  3703MB/s ± 0%  +1765.85%  (p=0.000 n=8+10)
CompareBytesBigIdentical     35.3TB/s ± 0%  28.5TB/s ± 0%    -19.31%  (p=0.000 n=8+8)

Change-Id: I112d9de2324986fd65ed237a86b11856a1c0f4a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/196837
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>