Re-land "Clusterfuzz identified overflow check needed in dehoisting."

src/utils.h

 // Copyright 2012 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_UTILS_H_
 #define V8_UTILS_H_
 
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "src/allocation.h"
 #include "src/base/macros.h"
 #include "src/checks.h"
 #include "src/globals.h"
 #include "src/list.h"
 #include "src/platform.h"
 #include "src/vector.h"
+#include "src/base/safe_math.h"
 
 namespace v8 {
 namespace internal {
 
 // ----------------------------------------------------------------------------
 // General helper functions
 
 // Returns true iff x is a power of 2. Cannot be used with the maximally
 // negative value of the type T (the -1 overflows).
 template <typename T>
@@ skipping 216 matching lines @@
 template<> struct make_unsigned<int32_t> {
   typedef uint32_t type;
 };
 
 
 template<> struct make_unsigned<int64_t> {
   typedef uint64_t type;
 };
 
 
+template<typename T> bool MultiplyOverflows(T x, T y) {

[danno, 2014/06/18 14:55:04]

Do you really need these wrappers? It seems that they make you do the math
twice. Is there really any downside to having the CheckedNumber<T> directly at
the site where it's used... and just using the checked_result.value()?

+  v8::base::internal::CheckedNumeric<T> checked_result = x;
+  checked_result = checked_result * y;
+  return !checked_result.IsValid();
+}
+
+
+template<typename T> bool AdditionOverflows(T x, T y) {
+  v8::base::internal::CheckedNumeric<T> checked_result = x;
+  checked_result = checked_result + y;
+  return !checked_result.IsValid();
+}
+
+
 // ----------------------------------------------------------------------------
 // BitField is a help template for encoding and decode bitfield with
 // unsigned content.
 
 template<class T, int shift, int size, class U>
 class BitFieldBase {
  public:
   // A type U mask of bit field.  To use all bits of a type U of x bits
   // in a bitfield without compiler warnings we have to compute 2^x
   // without using a shift count of x in the computation.
@@ skipping 1309 matching lines @@
   // Add formatted contents like printf based on a va_list.
   void AddFormattedList(const char* format, va_list list);
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(StringBuilder);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_UTILS_H_