Use std::piecewise_constant_distribution instead of ad-hoc binary search.

Summary:
Fix the issue with the most recently discovered unit receiving much less attention.

Note: I had to change the seed for one test to make it pass. Alternatively,
the number of runs could be increased. I believe that the average time of
'foo' discovery is not increased, just seed=1 was particularly convenient
for the previous PRNG scheme used.

Reviewers: aizatsky, kcc

Subscribers: llvm-commits, kcc

Differential Revision: http://reviews.llvm.org/D16419

llvm-svn: 258473

1 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/Fuzzer/FuzzerInterface.h b/llvm/lib/Fuzzer/FuzzerInterface.h
index 64b8f868f65..5cf0361e1e6 100644
--- a/llvm/lib/Fuzzer/FuzzerInterface.h
+++ b/llvm/lib/Fuzzer/FuzzerInterface.h
@@ -66,6 +66,18 @@ class FuzzerRandomBase {
   // Return a random number in range [0,n).
   size_t operator()(size_t n) { return n ? Rand() % n : 0; }
   bool RandBool() { return Rand() % 2; }
+
+  // The methods below is to satisfy UniformRandomNumberGenerator:
+  // http://en.cppreference.com/w/cpp/concept/UniformRandomNumberGenerator\
+
+  // Returns a random number between 0 and RAND_MAX inclusive.
+  double operator()() { return operator()(RAND_MAX); }
+
+  // Returns the smallest value that operator() may return.
+  double min() { return 0; }
+
+  // Returns the largest value that operator() may return.
+  double max() { return RAND_MAX; }
 };
 
 // Using libc's stand/rand.