cmd/compile: add rules to optimize go codes to constant 0 on loong64

cmd/compile: add rules to optimize go codes to constant 0 on loong64

goos: linux
goarch: loong64
pkg: test/bench/go1
cpu: Loongson-3A6000 @ 2500.00MHz
                      │  old.bench  │             new.bench              │
                      │   sec/op    │   sec/op     vs base               │
BinaryTree17             7.735 ± 1%    7.716 ± 1%  -0.23% (p=0.041 n=15)
Fannkuch11               2.645 ± 0%    2.646 ± 0%  +0.05% (p=0.013 n=15)
FmtFprintfEmpty         35.87n ± 0%   35.89n ± 0%  +0.06% (p=0.000 n=15)
FmtFprintfString        59.54n ± 0%   59.47n ± 0%       ~ (p=0.213 n=15)
FmtFprintfInt           62.23n ± 0%   62.06n ± 0%       ~ (p=0.212 n=15)
FmtFprintfIntInt        98.16n ± 0%   97.90n ± 0%  -0.26% (p=0.000 n=15)
FmtFprintfPrefixedInt   117.0n ± 0%   116.7n ± 0%  -0.26% (p=0.000 n=15)
FmtFprintfFloat         204.6n ± 0%   204.2n ± 0%  -0.20% (p=0.000 n=15)
FmtManyArgs             456.3n ± 0%   455.4n ± 0%  -0.20% (p=0.000 n=15)
GobDecode               7.210m ± 0%   7.156m ± 1%  -0.75% (p=0.000 n=15)
GobEncode               8.143m ± 1%   8.177m ± 1%       ~ (p=0.806 n=15)
Gzip                    280.2m ± 0%   279.7m ± 0%  -0.19% (p=0.005 n=15)
Gunzip                  32.71m ± 0%   32.65m ± 0%  -0.19% (p=0.000 n=15)
HTTPClientServer        53.76µ ± 0%   53.65µ ± 0%       ~ (p=0.083 n=15)
JSONEncode              9.297m ± 0%   9.295m ± 0%       ~ (p=0.806 n=15)
JSONDecode              46.97m ± 1%   47.07m ± 1%       ~ (p=0.683 n=15)
Mandelbrot200           4.602m ± 0%   4.600m ± 0%  -0.05% (p=0.001 n=15)
GoParse                 4.682m ± 0%   4.670m ± 1%  -0.25% (p=0.001 n=15)
RegexpMatchEasy0_32     59.80n ± 0%   59.63n ± 0%  -0.28% (p=0.000 n=15)
RegexpMatchEasy0_1K     458.3n ± 0%   457.3n ± 0%  -0.22% (p=0.001 n=15)
RegexpMatchEasy1_32     59.39n ± 0%   59.23n ± 0%  -0.27% (p=0.000 n=15)
RegexpMatchEasy1_1K     557.9n ± 0%   556.6n ± 0%  -0.23% (p=0.001 n=15)
RegexpMatchMedium_32    803.6n ± 0%   801.8n ± 0%  -0.22% (p=0.001 n=15)
RegexpMatchMedium_1K    27.32µ ± 0%   27.26µ ± 0%  -0.21% (p=0.000 n=15)
RegexpMatchHard_32      1.385µ ± 0%   1.382µ ± 0%  -0.22% (p=0.000 n=15)
RegexpMatchHard_1K      40.93µ ± 0%   40.83µ ± 0%  -0.24% (p=0.000 n=15)
Revcomp                 474.8m ± 0%   474.3m ± 0%       ~ (p=0.250 n=15)
Template                77.41m ± 1%   76.63m ± 1%  -1.01% (p=0.023 n=15)
TimeParse               271.1n ± 0%   271.2n ± 0%  +0.04% (p=0.022 n=15)
TimeFormat              290.0n ± 0%   289.8n ± 0%       ~ (p=0.118 n=15)
geomean                 51.73µ        51.64µ       -0.18%

Change-Id: I45a1e6c85bb3cea0f62766ec932432803e9af10a
Reviewed-on: https://go-review.googlesource.com/c/go/+/619315
Reviewed-by: Qiqi Huang <huangqiqi@loongson.cn>
Reviewed-by: Meidan Li <limeidan@loongson.cn>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>