[ARMTargetParser] Adding a few more CPUs for Clang CPU detection. NFC.

[oota-llvm.git] / include / llvm / Support / RandomNumberGenerator.h

diff --git a/include/llvm/Support/RandomNumberGenerator.h b/include/llvm/Support/RandomNumberGenerator.h
index 84fcdcbc76adf840ccb62cfdc95110b612327c79..7446558f0c8811b551ef33de5548ab50b04877ac 100644 (file)
--- a/include/llvm/Support/RandomNumberGenerator.h
+++ b/include/llvm/Support/RandomNumberGenerator.h
@@ -7,9 +7,9 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file defines an abstraction for random number generation (RNG).
-// Note that the current implementation is not cryptographically secure
-// as it uses the C++11 <random> facilities.
+// This file defines an abstraction for deterministic random number
+// generation (RNG).  Note that the current implementation is not
+// cryptographically secure as it uses the C++11 <random> facilities.
 //
 //===----------------------------------------------------------------------===//
 
@@ -17,36 +17,41 @@
 #define LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_
 
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/DataTypes.h" // Needed for uint64_t on Windows.
 #include <random>
 
 namespace llvm {
 
 /// A random number generator.
-/// Instances of this class should not be shared across threads.
+///
+/// Instances of this class should not be shared across threads. The
+/// seed should be set by passing the -rng-seed=<uint64> option. Use
+/// Module::createRNG to create a new RNG instance for use with that
+/// module.
 class RandomNumberGenerator {
 public:
-  /// Seeds and salts the underlying RNG engine. The salt of type StringRef
-  /// is passed into the constructor. The seed can be set on the command
-  /// line via -rng-seed=<uint64>.
-  /// The reason for the salt is to ensure different random streams even if
-  /// the same seed is used for multiple invocations of the compiler.
-  /// A good salt value should add additional entropy and be constant across
-  /// different machines (i.e., no paths) to allow for reproducible builds.
-  /// An instance of this class can be retrieved from the current Module.
-  /// \see Module::getRNG
-  RandomNumberGenerator(StringRef Salt);
-
   /// Returns a random number in the range [0, Max).
-  uint64_t next(uint64_t Max);
+  uint_fast64_t operator()();
 
 private:
+  /// Seeds and salts the underlying RNG engine.
+  ///
+  /// This constructor should not be used directly. Instead use
+  /// Module::createRNG to create a new RNG salted with the Module ID.
+  RandomNumberGenerator(StringRef Salt);
+
   // 64-bit Mersenne Twister by Matsumoto and Nishimura, 2000
   // http://en.cppreference.com/w/cpp/numeric/random/mersenne_twister_engine
+  // This RNG is deterministically portable across C++11
+  // implementations.
   std::mt19937_64 Generator;
 
   // Noncopyable.
   RandomNumberGenerator(const RandomNumberGenerator &other) = delete;
   RandomNumberGenerator &operator=(const RandomNumberGenerator &other) = delete;
+
+  friend class Module;
 };
 }