Revert of Implement xorshift128+ for Math.random.

src/runtime/runtime-maths.cc

Index: src/runtime/runtime-maths.cc
diff --git a/src/runtime/runtime-maths.cc b/src/runtime/runtime-maths.cc
index cb44c60113cc9c49469d39f86344627f0b8b8405..70c587d7454b401fbfe9f2fc61812b039a6a0531 100644
--- a/src/runtime/runtime-maths.cc
+++ b/src/runtime/runtime-maths.cc
@@ -247,48 +247,18 @@
 }
 
 
-RUNTIME_FUNCTION(Runtime_GenerateRandomNumbers) {
-  HandleScope scope(isolate);
-  DCHECK(args.length() == 1);
-  static const int kState0Offset = 0;
-  static const int kState1Offset = 1;
-  static const int kRandomBatchSize = 64;
-  CONVERT_ARG_HANDLE_CHECKED(Object, maybe_typed_array, 0);
-  Handle<JSTypedArray> typed_array;
-  // Allocate typed array if it does not yet exist.
-  if (maybe_typed_array->IsJSTypedArray()) {
-    typed_array = Handle<JSTypedArray>::cast(maybe_typed_array);
-  } else {
-    static const int kByteLength = kRandomBatchSize * kDoubleSize;
-    Handle<JSArrayBuffer> buffer =
-        isolate->factory()->NewJSArrayBuffer(SharedFlag::kNotShared, TENURED);
-    JSArrayBuffer::SetupAllocatingData(buffer, isolate, kByteLength, true,
-                                       SharedFlag::kNotShared);
-    typed_array = isolate->factory()->NewJSTypedArray(
-        kExternalFloat64Array, buffer, 0, kRandomBatchSize);
-  }
-
-  DisallowHeapAllocation no_gc;
-  double* array =
-      reinterpret_cast<double*>(typed_array->GetBuffer()->backing_store());
-  // Fetch existing state.
-  uint64_t state0 = double_to_uint64(array[kState0Offset]);
-  uint64_t state1 = double_to_uint64(array[kState1Offset]);
-  // Initialize state if not yet initialized.
-  while (state0 == 0 || state1 == 0) {
-    isolate->random_number_generator()->NextBytes(&state0, sizeof(state0));
-    isolate->random_number_generator()->NextBytes(&state1, sizeof(state1));
-  }
-  // Create random numbers.
-  for (int i = kState1Offset + 1; i < kRandomBatchSize; i++) {
-    // Generate random numbers using xorshift128+.
-    base::RandomNumberGenerator::XorShift128(&state0, &state1);
-    array[i] = base::RandomNumberGenerator::ToDouble(state0, state1);
-  }
-  // Persist current state.
-  array[kState0Offset] = uint64_to_double(state0);
-  array[kState1Offset] = uint64_to_double(state1);
-  return *typed_array;
+RUNTIME_FUNCTION(Runtime_InitializeRNG) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 0);
+  static const int kSize = 4;
+  Handle<FixedArray> array = isolate->factory()->NewFixedArray(kSize);
+  uint16_t seeds[kSize];
+  do {
+    isolate->random_number_generator()->NextBytes(seeds,
+                                                  kSize * sizeof(*seeds));
+  } while (!(seeds[0] && seeds[1] && seeds[2] && seeds[3]));
+  for (int i = 0; i < kSize; i++) array->set(i, Smi::FromInt(seeds[i]));
+  return *isolate->factory()->NewJSArrayWithElements(array);
 }
 }  // namespace internal
 }  // namespace v8