[builtins] Introduce proper base::ieee754::log.

src/profiler/sampling-heap-profiler.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/profiler/sampling-heap-profiler.h"
 
 #include <stdint.h>
 #include <memory>
 #include "src/api.h"
+#include "src/base/ieee754.h"
 #include "src/base/utils/random-number-generator.h"
 #include "src/frames-inl.h"
 #include "src/heap/heap.h"
 #include "src/isolate.h"
 #include "src/profiler/strings-storage.h"
 
 namespace v8 {
 namespace internal {
 
 // We sample with a Poisson process, with constant average sampling interval.
 // This follows the exponential probability distribution with parameter
 // λ = 1/rate where rate is the average number of bytes between samples.
 //
 // Let u be a uniformly distributed random number between 0 and 1, then
 // next_sample = (- ln u) / λ
 intptr_t SamplingAllocationObserver::GetNextSampleInterval(uint64_t rate) {
   if (FLAG_sampling_heap_profiler_suppress_randomness) {
     return static_cast<intptr_t>(rate);
   }
   double u = random_->NextDouble();
-  double next = (-std::log(u)) * rate;
+  double next = (-base::ieee754::log(u)) * rate;
   return next < kPointerSize
              ? kPointerSize
              : (next > INT_MAX ? INT_MAX : static_cast<intptr_t>(next));
 }
 
 // Samples were collected according to a poisson process. Since we have not
 // recorded all allocations, we must approximate the shape of the underlying
 // space of allocations based on the samples we have collected. Given that
 // we sample at rate R, the probability that an allocation of size S will be
 // sampled is 1-exp(-S/R). This function uses the above probability to
@@ skipping 230 matching lines @@
     }
   }
   auto profile = new v8::internal::AllocationProfile();
   TranslateAllocationNode(profile, &profile_root_, scripts);
   return profile;
 }
 
 
 }  // namespace internal
 }  // namespace v8