crypto/sha256: use const table for key loading on loong64

crypto/sha256: use const table for key loading on loong64

Load constant keys from a static memory table rather than loading immediates into registers on loong64.

Benchmark for Loongson-3A5000:
goos: linux
goarch: loong64
pkg: crypto/sha256
cpu: Loongson-3A5000-HV @ 2500.00MHz
                    │   sha256o   │              sha256n              │
                    │   sec/op    │   sec/op     vs base              │
Hash8Bytes/New-4      356.1n ± 0%   347.0n ± 0%  -2.54% (p=0.000 n=8)
Hash8Bytes/Sum224-4   368.7n ± 0%   359.5n ± 0%  -2.50% (p=0.000 n=8)
Hash8Bytes/Sum256-4   367.7n ± 0%   358.9n ± 0%  -2.41% (p=0.000 n=8)
Hash1K/New-4          4.741µ ± 0%   4.578µ ± 0%  -3.44% (p=0.000 n=8)
Hash1K/Sum224-4       4.755µ ± 0%   4.591µ ± 0%  -3.44% (p=0.000 n=8)
Hash1K/Sum256-4       4.753µ ± 0%   4.589µ ± 0%  -3.46% (p=0.000 n=8)
Hash8K/New-4          35.42µ ± 0%   34.19µ ± 0%  -3.45% (p=0.000 n=8)
Hash8K/Sum224-4       35.43µ ± 0%   34.21µ ± 0%  -3.44% (p=0.000 n=8)
Hash8K/Sum256-4       35.46µ ± 0%   34.22µ ± 0%  -3.48% (p=0.000 n=8)
Hash256K/New-4        1.138m ± 0%   1.098m ± 0%  -3.54% (p=0.000 n=8)
Hash256K/Sum224-4     1.138m ± 0%   1.098m ± 0%  -3.53% (p=0.000 n=8)
Hash256K/Sum256-4     1.139m ± 0%   1.099m ± 0%  -3.48% (p=0.000 n=8)
Hash1M/New-4          4.488m ± 0%   4.388m ± 0%  -2.22% (p=0.000 n=8)
Hash1M/Sum224-4       4.488m ± 0%   4.387m ± 0%  -2.24% (p=0.000 n=8)
Hash1M/Sum256-4       4.489m ± 0%   4.388m ± 0%  -2.25% (p=0.000 n=8)
geomean               50.02µ        48.50µ       -3.03%

                    │   sha256o    │              sha256n               │
                    │     B/s      │     B/s       vs base              │
Hash8Bytes/New-4      21.42Mi ± 0%   21.99Mi ± 0%  +2.63% (p=0.000 n=8)
Hash8Bytes/Sum224-4   20.69Mi ± 0%   21.22Mi ± 0%  +2.56% (p=0.000 n=8)
Hash8Bytes/Sum256-4   20.74Mi ± 0%   21.26Mi ± 0%  +2.48% (p=0.000 n=8)
Hash1K/New-4          206.0Mi ± 0%   213.3Mi ± 0%  +3.57% (p=0.000 n=8)
Hash1K/Sum224-4       205.4Mi ± 0%   212.7Mi ± 0%  +3.57% (p=0.000 n=8)
Hash1K/Sum256-4       205.5Mi ± 0%   212.8Mi ± 0%  +3.58% (p=0.000 n=8)
Hash8K/New-4          220.6Mi ± 0%   228.5Mi ± 0%  +3.58% (p=0.000 n=8)
Hash8K/Sum224-4       220.5Mi ± 0%   228.4Mi ± 0%  +3.56% (p=0.000 n=8)
Hash8K/Sum256-4       220.3Mi ± 0%   228.3Mi ± 0%  +3.61% (p=0.000 n=8)
Hash256K/New-4        219.7Mi ± 0%   227.7Mi ± 0%  +3.67% (p=0.000 n=8)
Hash256K/Sum224-4     219.6Mi ± 0%   227.6Mi ± 0%  +3.66% (p=0.000 n=8)
Hash256K/Sum256-4     219.6Mi ± 0%   227.5Mi ± 0%  +3.60% (p=0.000 n=8)
Hash1M/New-4          222.8Mi ± 0%   227.9Mi ± 0%  +2.27% (p=0.000 n=8)
Hash1M/Sum224-4       222.8Mi ± 0%   227.9Mi ± 0%  +2.29% (p=0.000 n=8)
Hash1M/Sum256-4       222.8Mi ± 0%   227.9Mi ± 0%  +2.30% (p=0.000 n=8)
geomean               136.0Mi        140.2Mi       +3.13%

Benchmark for Loongson-3A6000:
goos: linux
goarch: loong64
pkg: crypto/sha256
cpu: Loongson-3A6000 @ 2500.00MHz
                    │ sha256.old  │             sha256.new             │
                    │   sec/op    │   sec/op     vs base               │
Hash8Bytes/New-8      294.5n ± 0%   288.6n ± 0%  -2.00% (p=0.000 n=10)
Hash8Bytes/Sum224-8   305.0n ± 0%   299.7n ± 0%  -1.74% (p=0.000 n=10)
Hash8Bytes/Sum256-8   302.0n ± 0%   296.8n ± 0%  -1.74% (p=0.000 n=10)
Hash1K/New-8          4.186µ ± 0%   4.096µ ± 0%  -2.15% (p=0.000 n=10)
Hash1K/Sum224-8       4.193µ ± 0%   4.104µ ± 0%  -2.12% (p=0.000 n=10)
Hash1K/Sum256-8       4.194µ ± 0%   4.108µ ± 0%  -2.04% (p=0.000 n=10)
Hash8K/New-8          31.44µ ± 0%   30.76µ ± 0%  -2.17% (p=0.000 n=10)
Hash8K/Sum224-8       31.45µ ± 0%   30.79µ ± 0%  -2.10% (p=0.000 n=10)
Hash8K/Sum256-8       31.45µ ± 0%   30.78µ ± 0%  -2.12% (p=0.000 n=10)
Hash256K/New-8        996.7µ ± 0%   975.6µ ± 0%  -2.12% (p=0.000 n=10)
Hash256K/Sum224-8     996.8µ ± 0%   975.8µ ± 0%  -2.11% (p=0.000 n=10)
Hash256K/Sum256-8     996.8µ ± 0%   975.6µ ± 0%  -2.12% (p=0.000 n=10)
Hash1M/New-8          3.987m ± 0%   3.904m ± 0%  -2.08% (p=0.000 n=10)
Hash1M/Sum224-8       3.990m ± 0%   3.902m ± 0%  -2.20% (p=0.000 n=10)
Hash1M/Sum256-8       3.987m ± 0%   3.903m ± 0%  -2.10% (p=0.000 n=10)
geomean               43.59µ        42.69µ       -2.06%

                    │  sha256.old  │             sha256.new              │
                    │     B/s      │     B/s       vs base               │
Hash8Bytes/New-8      25.90Mi ± 0%   26.44Mi ± 0%  +2.06% (p=0.000 n=10)
Hash8Bytes/Sum224-8   25.01Mi ± 0%   25.46Mi ± 0%  +1.77% (p=0.000 n=10)
Hash8Bytes/Sum256-8   25.26Mi ± 0%   25.72Mi ± 0%  +1.79% (p=0.000 n=10)
Hash1K/New-8          233.3Mi ± 0%   238.5Mi ± 0%  +2.19% (p=0.000 n=10)
Hash1K/Sum224-8       232.9Mi ± 0%   238.0Mi ± 0%  +2.17% (p=0.000 n=10)
Hash1K/Sum256-8       232.9Mi ± 0%   237.7Mi ± 0%  +2.07% (p=0.000 n=10)
Hash8K/New-8          248.5Mi ± 0%   254.0Mi ± 0%  +2.22% (p=0.000 n=10)
Hash8K/Sum224-8       248.4Mi ± 0%   253.7Mi ± 0%  +2.14% (p=0.000 n=10)
Hash8K/Sum256-8       248.4Mi ± 0%   253.8Mi ± 0%  +2.17% (p=0.000 n=10)
Hash256K/New-8        250.8Mi ± 0%   256.3Mi ± 0%  +2.17% (p=0.000 n=10)
Hash256K/Sum224-8     250.8Mi ± 0%   256.2Mi ± 0%  +2.16% (p=0.000 n=10)
Hash256K/Sum256-8     250.8Mi ± 0%   256.2Mi ± 0%  +2.17% (p=0.000 n=10)
Hash1M/New-8          250.8Mi ± 0%   256.2Mi ± 0%  +2.12% (p=0.000 n=10)
Hash1M/Sum224-8       250.6Mi ± 0%   256.3Mi ± 0%  +2.25% (p=0.000 n=10)
Hash1M/Sum256-8       250.8Mi ± 0%   256.2Mi ± 0%  +2.14% (p=0.000 n=10)
geomean               156.0Mi        159.3Mi       +2.11%

Change-Id: Ib72cf3c746d4ad73e52e5d31f6b4a834fd36d934
Reviewed-on: https://go-review.googlesource.com/c/go/+/678435
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: sophie zhao <zhaoxiaolin@loongson.cn>
Reviewed-by: Mark Freeman <markfreeman@google.com>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>