runtime: using wyrand for fastrand on linux/loong64

Benchmarks on linux/loong64:
name               old time/op    new time/op    delta
Fastrand           4.06ns ± 0%    3.60ns ± 0%    -11.29%  (p=0.000 n=32+27)
Fastrand64         7.20ns ± 0%    7.16ns ± 0%     -0.52%  (p=0.000 n=23+31)
FastrandHashiter   49.5ns ± 1%    48.9ns ± 2%     -1.24%  (p=0.000 n=32+32)
Fastrandn/2        4.45ns ± 0%    3.81ns ± 0%    -14.37%  (p=0.000 n=32+32)
Fastrandn/3        4.45ns ± 0%    3.81ns ± 0%    -14.32%  (p=0.000 n=32+32)
Fastrandn/4        4.45ns ± 0%    3.81ns ± 0%    -14.33%  (p=0.000 n=31+32)
Fastrandn/5        4.44ns ± 0%    3.81ns ± 0%    -14.26%  (p=0.000 n=31+30)

Change-Id: I0aba7d2331221426c44cc0d0dddecca3b585fda4
Reviewed-on: https://go-review.googlesource.com/c/go/+/446896
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Wayne Zuo <wdvxdr@golangcn.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

Author: abner-chenc

src/runtime/stubs.go

@@ -131,7 +131,7 @@ func fastrand() uint32 {
 	// by the compiler should be in this list.
 	if goarch.IsAmd64|goarch.IsArm64|goarch.IsPpc64|
 		goarch.IsPpc64le|goarch.IsMips64|goarch.IsMips64le|
-		goarch.IsS390x|goarch.IsRiscv64 == 1 {
+		goarch.IsS390x|goarch.IsRiscv64|goarch.IsLoong64 == 1 {
 		mp.fastrand += 0xa0761d6478bd642f
 		hi, lo := math.Mul64(mp.fastrand, mp.fastrand^0xe7037ed1a0b428db)
 		return uint32(hi ^ lo)