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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 |
| 26 // and implementation. I expect the implementation is different and |
| 27 // therefore the tests would need to be changed. |
25 cl::opt<unsigned long long> | 28 cl::opt<unsigned long long> |
26 RandomSeed("rng-seed", cl::desc("Seed the random number generator"), | 29 RandomSeed("sz-seed", cl::desc("Seed the random number generator"), |
27 cl::init(time(0))); | 30 cl::init(time(0))); |
28 | 31 |
29 const unsigned MAX = 2147483647; | 32 const unsigned MAX = 2147483647; |
30 | 33 |
31 } // end of anonymous namespace | 34 } // end of anonymous namespace |
32 | 35 |
33 // 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. |
34 // | 37 // |
35 // 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 |
36 // 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 |
37 // 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 |
38 // attacker can't introspect. | 41 // attacker can't introspect. |
39 RandomNumberGenerator::RandomNumberGenerator(llvm::StringRef) | 42 RandomNumberGenerator::RandomNumberGenerator(llvm::StringRef) |
40 : State(RandomSeed) {} | 43 : State(RandomSeed) {} |
41 | 44 |
42 uint64_t RandomNumberGenerator::next(uint64_t Max) { | 45 uint64_t RandomNumberGenerator::next(uint64_t Max) { |
43 // Lewis, Goodman, and Miller (1969) | 46 // Lewis, Goodman, and Miller (1969) |
44 State = (16807 * State) % MAX; | 47 State = (16807 * State) % MAX; |
45 return State % Max; | 48 return State % Max; |
46 } | 49 } |
47 | 50 |
48 bool RandomNumberGeneratorWrapper::getTrueWithProbability(float Probability) { | 51 bool RandomNumberGeneratorWrapper::getTrueWithProbability(float Probability) { |
49 return RNG.next(MAX) < Probability * MAX; | 52 return RNG.next(MAX) < Probability * MAX; |
50 } | 53 } |
51 | 54 |
52 } // end of namespace Ice | 55 } // end of namespace Ice |
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