Create TimeBase for time related classes.

src/base/bits.h

 // Copyright 2014 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.
 
 #ifndef V8_BASE_BITS_H_
 #define V8_BASE_BITS_H_
 
 #include <stdint.h>
 #include "src/base/macros.h"
 #if V8_CC_MSVC
 #include <intrin.h>
 #endif
 #if V8_OS_WIN32
 #include "src/base/win32-headers.h"
 #endif
 
 namespace v8 {
 namespace base {
+
+namespace internal {

[jochen (gone - plz use gerrit), 2016/05/06 09:43:02]

safe_math.h has using internal::CheckedNumeric in namespace base, so why is this
needed here?

[lpy, 2016/05/06 17:23:23]

It's used in the declaration of FromCheckedNumeric.

+template <typename T>
+class CheckedNumeric;
+}
+
 namespace bits {
 
 // CountPopulation32(value) returns the number of bits set in |value|.
 inline unsigned CountPopulation32(uint32_t value) {
 #if V8_HAS_BUILTIN_POPCOUNT
   return __builtin_popcount(value);
 #else
   value = ((value >> 1) & 0x55555555) + (value & 0x55555555);
   value = ((value >> 2) & 0x33333333) + (value & 0x33333333);
   value = ((value >> 4) & 0x0f0f0f0f) + (value & 0x0f0f0f0f);
@@ skipping 260 matching lines @@
   return rhs ? lhs / rhs : 0u;
 }
 
 
 // UnsignedMod32(lhs, rhs) divides |lhs| by |rhs| and returns the remainder
 // truncated to uint32. If |rhs| is zero, then zero is returned.
 inline uint32_t UnsignedMod32(uint32_t lhs, uint32_t rhs) {
   return rhs ? lhs % rhs : 0u;
 }
 
+
+// Clamp |value| on overflow and underflow conditions.
+int64_t FromCheckedNumeric(const internal::CheckedNumeric<int64_t> value);
+
+
+// SignedSaturatedAdd64(lhs, rhs) adds |lhs| and |rhs|,
+// checks and returns the result.
+int64_t SignedSaturatedAdd64(int64_t lhs, int64_t rhs);
+
+
+// SignedSaturatedSub64(lhs, rhs) substracts |lhs| by |rhs|,
+// checks and returns the result.
+int64_t SignedSaturatedSub64(int64_t lhs, int64_t rhs);
+
+
 }  // namespace bits
 }  // namespace base
 }  // namespace v8
 
 #endif  // V8_BASE_BITS_H_