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| 1 //===- subzero/src/IceRNG.cpp - PRNG implementation -----------------------===// | 1 //===- subzero/src/IceRNG.cpp - PRNG implementation -----------------------===// |
| 2 // | 2 // |
| 3 // The Subzero Code Generator | 3 // The Subzero Code Generator |
| 4 // | 4 // |
| 5 // This file is distributed under the University of Illinois Open Source | 5 // This file is distributed under the University of Illinois Open Source |
| 6 // License. See LICENSE.TXT for details. | 6 // License. See LICENSE.TXT for details. |
| 7 // | 7 // |
| 8 //===----------------------------------------------------------------------===// | 8 //===----------------------------------------------------------------------===// |
| 9 // | 9 // |
| 10 // This file implements the random number generator. | 10 // This file implements the random number generator. |
| 11 // | 11 // |
| 12 //===----------------------------------------------------------------------===// | 12 //===----------------------------------------------------------------------===// |
| 13 | 13 |
| 14 #include <time.h> | 14 #include <time.h> |
| 15 | 15 |
| 16 #include "llvm/Support/CommandLine.h" | 16 #include "llvm/Support/CommandLine.h" |
| 17 | 17 |
| 18 #include "IceRNG.h" | 18 #include "IceRNG.h" |
| 19 | 19 |
| 20 namespace Ice { | 20 namespace Ice { |
| 21 | 21 |
| 22 namespace { | 22 namespace { |
| 23 namespace cl = llvm::cl; | 23 namespace cl = llvm::cl; |
| 24 | 24 |
| 25 // TODO(stichnot): See if we can easily use LLVM's -rng-seed option | 25 // TODO(stichnot): See if we can easily use LLVM's -rng-seed option |
| 26 // and implementation. I expect the implementation is different and | 26 // and implementation. I expect the implementation is different and |
| 27 // therefore the tests would need to be changed. | 27 // therefore the tests would need to be changed. |
| 28 cl::opt<unsigned long long> | 28 cl::opt<unsigned long long> |
| 29 RandomSeed("sz-seed", cl::desc("Seed the random number generator"), | 29 RandomSeed("sz-seed", cl::desc("Seed the random number generator"), |
| 30 cl::init(time(0))); | 30 cl::init(time(0))); |
| 31 | 31 |
| 32 const unsigned MAX = 2147483647; | 32 const unsigned MAX = 2147483647; |
| 33 | 33 |
| 34 } // end of anonymous namespace | 34 } // end of anonymous namespace |
| 35 | 35 |
| 36 // TODO(wala,stichnot): Switch to RNG implementation from LLVM or C++11. | 36 // TODO(wala,stichnot): Switch to RNG implementation from LLVM or C++11. |
| 37 // | 37 // |
| 38 // TODO(wala,stichnot): Make it possible to replay the RNG sequence in a | 38 // TODO(wala,stichnot): Make it possible to replay the RNG sequence in a |
| 39 // subsequent run, for reproducing a bug. Print the seed in a comment | 39 // subsequent run, for reproducing a bug. Print the seed in a comment |
| 40 // in the asm output. Embed the seed in the binary via metadata that an | 40 // in the asm output. Embed the seed in the binary via metadata that an |
| 41 // attacker can't introspect. | 41 // attacker can't introspect. |
| 42 RandomNumberGenerator::RandomNumberGenerator(llvm::StringRef) | 42 RandomNumberGenerator::RandomNumberGenerator(llvm::StringRef) |
| 43 : State(RandomSeed) {} | 43 : State(RandomSeed) {} |
| 44 | 44 |
| 45 uint64_t RandomNumberGenerator::next(uint64_t Max) { | 45 uint64_t RandomNumberGenerator::next(uint64_t Max) { |
| 46 // Lewis, Goodman, and Miller (1969) | 46 // Lewis, Goodman, and Miller (1969) |
| 47 State = (16807 * State) % MAX; | 47 State = (16807 * State) % MAX; |
| 48 return State % Max; | 48 return State % Max; |
| 49 } | 49 } |
| 50 | 50 |
| 51 bool RandomNumberGeneratorWrapper::getTrueWithProbability(float Probability) { | 51 bool RandomNumberGeneratorWrapper::getTrueWithProbability(float Probability) { |
| 52 return RNG.next(MAX) < Probability * MAX; | 52 return RNG.next(MAX) < Probability * MAX; |
| 53 } | 53 } |
| 54 | 54 |
| 55 } // end of namespace Ice | 55 } // end of namespace Ice |
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