Move platform abstraction to base library

src/base/macros.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_MACROS_H_
 #define V8_BASE_MACROS_H_
 
 #include "include/v8stdint.h"
 #include "src/base/build_config.h"
+#include "src/base/logging.h"
 
 
 // The expression OFFSET_OF(type, field) computes the byte-offset
 // of the specified field relative to the containing type. This
 // corresponds to 'offsetof' (in stddef.h), except that it doesn't
 // use 0 or NULL, which causes a problem with the compiler warnings
 // we have enabled (which is also why 'offsetof' doesn't seem to work).
 // Here we simply use the non-zero value 4, which seems to work.
 #define OFFSET_OF(type, field)                                          \
   (reinterpret_cast<intptr_t>(&(reinterpret_cast<type*>(4)->field)) - 4)
@@ skipping 87 matching lines @@
 
 // The USE(x) template is used to silence C++ compiler warnings
 // issued for (yet) unused variables (typically parameters).
 template <typename T>
 inline void USE(T) { }
 
 
 #define IS_POWER_OF_TWO(x) ((x) != 0 && (((x) & ((x) - 1)) == 0))
 
 
+// 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>
+inline bool IsPowerOf2(T x) {
+  return IS_POWER_OF_TWO(x);

[tfarina, 2014/07/01 16:01:32]

Do we need to have the macro version?

[Sven Panne, 2014/07/02 08:18:41]

Yes, because it is used in STATIC_ASSERTs. When we have C++ 11, we can
inline+nuke the macro...

+}
+
+
 // Define our own macros for writing 64-bit constants.  This is less fragile
 // than defining __STDC_CONSTANT_MACROS before including <stdint.h>, and it
 // works on compilers that don't have it (like MSVC).
 #if V8_CC_MSVC
 # define V8_UINT64_C(x)   (x ## UI64)
 # define V8_INT64_C(x)    (x ## I64)
 # if V8_HOST_ARCH_64_BIT
 #  define V8_INTPTR_C(x)  (x ## I64)
 #  define V8_PTR_PREFIX   "ll"
 # else
@@ skipping 30 matching lines @@
 #if V8_OS_MACOSX
 #undef V8PRIxPTR
 #define V8PRIxPTR "lx"
 #endif
 
 // The following macro works on both 32 and 64-bit platforms.
 // Usage: instead of writing 0x1234567890123456
 //      write V8_2PART_UINT64_C(0x12345678,90123456);
 #define V8_2PART_UINT64_C(a, b) (((static_cast<uint64_t>(a) << 32) + 0x##b##u))
 
+
+// Compute the 0-relative offset of some absolute value x of type T.
+// This allows conversion of Addresses and integral types into
+// 0-relative int offsets.
+template <typename T>
+inline intptr_t OffsetFrom(T x) {
+  return x - static_cast<T>(0);
+}
+
+
+// Compute the absolute value of type T for some 0-relative offset x.
+// This allows conversion of 0-relative int offsets into Addresses and
+// integral types.
+template <typename T>
+inline T AddressFrom(intptr_t x) {
+  return static_cast<T>(static_cast<T>(0) + x);
+}
+
+
+// Return the largest multiple of m which is <= x.
+template <typename T>
+inline T RoundDown(T x, intptr_t m) {
+  ASSERT(IsPowerOf2(m));
+  return AddressFrom<T>(OffsetFrom(x) & -m);
+}
+
+
+// Return the smallest multiple of m which is >= x.
+template <typename T>
+inline T RoundUp(T x, intptr_t m) {
+  return RoundDown<T>(static_cast<T>(x + m - 1), m);
+}
+
+
+// Increment a pointer until it has the specified alignment.
+// This works like RoundUp, but it works correctly on pointer types where
+// sizeof(*pointer) might not be 1.
+template<class T>
+T AlignUp(T pointer, size_t alignment) {
+  ASSERT(sizeof(pointer) == sizeof(uintptr_t));
+  uintptr_t pointer_raw = reinterpret_cast<uintptr_t>(pointer);
+  return reinterpret_cast<T>(RoundUp(pointer_raw, alignment));
+}
+
+
+template <typename T, typename U>
+inline bool IsAligned(T value, U alignment) {
+  return (value & (alignment - 1)) == 0;
+}
+
+
+// Returns the smallest power of two which is >= x. If you pass in a
+// number that is already a power of two, it is returned as is.
+// Implementation is from "Hacker's Delight" by Henry S. Warren, Jr.,
+// figure 3-3, page 48, where the function is called clp2.
+inline uint32_t RoundUpToPowerOf2(uint32_t x) {
+  ASSERT(x <= 0x80000000u);
+  x = x - 1;
+  x = x | (x >> 1);
+  x = x | (x >> 2);
+  x = x | (x >> 4);
+  x = x | (x >> 8);
+  x = x | (x >> 16);
+  return x + 1;
+}
+
+
+inline uint32_t RoundDownToPowerOf2(uint32_t x) {
+  uint32_t rounded_up = RoundUpToPowerOf2(x);
+  if (rounded_up > x) return rounded_up >> 1;
+  return rounded_up;
+}
+
 #endif   // V8_BASE_MACROS_H_