Subzero: Add a random number generator.

src/IceRNG.h

+//===- subzero/src/IceRNG.h - Random number generator -----------*- C++ -*-===//
+//
+//                        The Subzero Code Generator
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares a random number generator.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SUBZERO_SRC_ICERNG_H
+#define SUBZERO_SRC_ICERNG_H
+
+#include <stdint.h>
+
+namespace Ice {
+
+// TODO: Replace with a cryptographically secure PRNG.
+class RandomNumberGenerator {
+public:
+  RandomNumberGenerator(uint64_t Seed) : State(Seed) {}
+
+  uint64_t next(uint64_t Bound) {
+    // Lewis, Goodman, and Miller (1969)
+    State = (16807 * State) % 2147483647;
+    return State % Bound;
+  }
+
+private:
+  uint64_t State;
+};
+
+}
+
+#endif // SUBZERO_SRC_ICERNG_H