[llvm] [Offload][Conformance] Add `RandomGenerator` for large input spaces (PR #154252)

[Ross Brunton via llvm-commits]

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@@ -0,0 +1,49 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the definition of the RandomState class, a fast and
+/// lightweight pseudo-random number generator.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef MATHTEST_RANDOMSTATE_HPP
+#define MATHTEST_RANDOMSTATE_HPP
+
+#include <cstdint>
+
+struct SeedTy {
+  uint64_t Value;
+};
+
+class [[nodiscard]] RandomState {
+  uint64_t State;
+
+  [[nodiscard]] static constexpr uint64_t splitMix64(uint64_t X) noexcept {
+    X += 0x9E3779B97F4A7C15ULL;
+    X = (X ^ (X >> 30)) * 0xBF58476D1CE4E5B9ULL;
+    X = (X ^ (X >> 27)) * 0x94D049BB133111EBULL;
+    X = (X ^ (X >> 31));
+    return X ? X : 0x9E3779B97F4A7C15ULL;
+  }
+
+public:
+  explicit constexpr RandomState(SeedTy Seed) noexcept
+      : State(splitMix64(Seed.Value)) {}
+
+  [[nodiscard]] inline uint64_t next() noexcept {
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RossBrunton wrote:

I don't think this should be `nodiscard`. I think it's reasonable for the user to call `next()` to advance the state of the RNG without using the value.

https://github.com/llvm/llvm-project/pull/154252