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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 cl::opt<unsigned long long> | 25 cl::opt<unsigned long long> |
26 RandomSeed("rng-seed", cl::desc("Seed the random number generator"), | 26 RandomSeed("rng-seed", cl::desc("Seed the random number generator"), |
27 cl::init(time(0))); | 27 cl::init(time(0))); |
28 | 28 |
| 29 const unsigned MAX = 2147483647; |
| 30 |
29 } // end of anonymous namespace | 31 } // end of anonymous namespace |
30 | 32 |
31 // TODO(wala,stichnot): Switch to RNG implementation from LLVM or C++11. | 33 // TODO(wala,stichnot): Switch to RNG implementation from LLVM or C++11. |
32 // | 34 // |
33 // TODO(wala,stichnot): Make it possible to replay the RNG sequence in a | 35 // TODO(wala,stichnot): Make it possible to replay the RNG sequence in a |
34 // subsequent run, for reproducing a bug. Print the seed in a comment | 36 // subsequent run, for reproducing a bug. Print the seed in a comment |
35 // in the asm output. Embed the seed in the binary via metadata that an | 37 // in the asm output. Embed the seed in the binary via metadata that an |
36 // attacker can't introspect. | 38 // attacker can't introspect. |
37 RandomNumberGenerator::RandomNumberGenerator(llvm::StringRef) | 39 RandomNumberGenerator::RandomNumberGenerator(llvm::StringRef) |
38 : State(RandomSeed) {} | 40 : State(RandomSeed) {} |
39 | 41 |
40 uint64_t RandomNumberGenerator::next(uint64_t Max) { | 42 uint64_t RandomNumberGenerator::next(uint64_t Max) { |
41 // Lewis, Goodman, and Miller (1969) | 43 // Lewis, Goodman, and Miller (1969) |
42 State = (16807 * State) % 2147483647; | 44 State = (16807 * State) % MAX; |
43 return State % Max; | 45 return State % Max; |
44 } | 46 } |
45 | 47 |
| 48 bool RandomNumberGeneratorWrapper::getTrueWithProbability(float Probability) { |
| 49 return RNG.next(MAX) < Probability * MAX; |
| 50 } |
| 51 |
46 } // end of namespace Ice | 52 } // end of namespace Ice |
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