Check in missing xoroshiro header from amo_ops testcase

test/sim/sw_testcases/include/xoroshiro.h

@@ -0,0 +1,50 @@
+#ifndef _XOROSHIRO256_H
+#define _XOROSHIRO256_H
+
+// xoroshiro256++ pseudorandom number generator.
+// Adapted from: https://prng.di.unimi.it/xoshiro256plusplus.c
+// Original copyright notice:
+
+/*  Written in 2019 by David Blackman and Sebastiano Vigna (vigna@acm.org)
+
+To the extent possible under law, the author has dedicated all copyright
+and related and neighboring rights to this software to the public domain
+worldwide. This software is distributed without any warranty.
+
+See <http://creativecommons.org/publicdomain/zero/1.0/>. */
+
+#include <stdint.h>
+
+/* This is xoshiro256++ 1.0, one of our all-purpose, rock-solid generators.
+   It has excellent (sub-ns) speed, a state (256 bits) that is large
+   enough for any parallel application, and it passes all tests we are
+   aware of.
+
+   For generating just floating-point numbers, xoshiro256+ is even faster.
+
+   The state must be seeded so that it is not everywhere zero. If you have
+   a 64-bit seed, we suggest to seed a splitmix64 generator and use its
+   output to fill s. */
+
+static inline uint64_t xr256_rotl(const uint64_t x, int k) {
+	return (x << k) | (x >> (64 - k));
+}
+
+uint64_t xr256_next(uint64_t s[4]) {
+	const uint64_t result = xr256_rotl(s[0] + s[3], 23) + s[0];
+
+	const uint64_t t = s[1] << 17;
+
+	s[2] ^= s[0];
+	s[3] ^= s[1];
+	s[1] ^= s[2];
+	s[0] ^= s[3];
+
+	s[2] ^= t;
+
+	s[3] = xr256_rotl(s[3], 45);
+
+	return result;
+}
+
+#endif