Reviewers: Sven Panne, Jakob,
Message:
Another trivial cleanup, PTAL.
Description:
Add V8_ALIGNOF() and use that in lazy-instance.h.
Also fix the inconsistent attribute naming.
Please review this at https://codereview.chromium.org/22888008/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files:
M include/v8config.h
M src/lazy-instance.h
Index: include/v8config.h
diff --git a/include/v8config.h b/include/v8config.h
index
aa24eebff50bb193543295723c9195ece613b8ec..72366fff85f99bc58ebf794e5f92a330e23e3f26
100644
--- a/include/v8config.h
+++ b/include/v8config.h
@@ -97,6 +97,7 @@
// C++11 feature detection
//
// V8_HAS_CXX11_ALIGNAS - alignas specifier supported
+// V8_HAS_CXX11_ALIGNOF - alignas operator supported
// V8_HAS_CXX11_STATIC_ASSERT - static_assert() supported
// V8_HAS_CXX11_DELETE - deleted functions supported
// V8_HAS_CXX11_FINAL - final marker supported
@@ -104,7 +105,9 @@
//
// Compiler-specific feature detection
//
-// V8_HAS_ATTRIBUTE___ALIGNED__ - __attribute__((__aligned__(n)))
supported
+// V8_HAS___ALIGNOF - __alignof(t) operator supported
+// V8_HAS___ALIGNOF__ - __alignof__(t) operator supported
+// V8_HAS_ATTRIBUTE_ALIGNED - __attribute__((aligned(n))) supported
// V8_HAS_ATTRIBUTE_ALWAYS_INLINE - __attribute__((always_inline))
supported
// V8_HAS_ATTRIBUTE_DEPRECATED - __attribute__((deprecated)) supported
// V8_HAS_ATTRIBUTE_VISIBILITY - __attribute__((visibility)) supported
@@ -122,7 +125,13 @@
# define V8_CC_CLANG 1
-# define V8_HAS_ATTRIBUTE___ALIGNED__ (__has_attribute(__aligned__))
+// If we pretend to be GCC 2.95 or newer, then we have to support
+// the GCC __alignof__ operator as well.
+#if __GNUC__ > 3 || (__GNUC__ >= 2 && __GNUC_MINOR__ >= 95)
+# define V8_HAS___ALIGNOF__ 1
+#endif
+
+# define V8_HAS_ATTRIBUTE_ALIGNED (__has_attribute(aligned))
# define V8_HAS_ATTRIBUTE_ALWAYS_INLINE (__has_attribute(always_inline))
# define V8_HAS_ATTRIBUTE_DEPRECATED (__has_attribute(deprecated))
# define V8_HAS_ATTRIBUTE_VISIBILITY (__has_attribute(visibility))
@@ -146,7 +155,9 @@
# define V8_CC_MINGW 1
# endif
-# define V8_HAS_ATTRIBUTE___ALIGNED__ (V8_GNUC_PREREQ(2, 95, 0))
+# define V8_HAS___ALIGNOF__ (V8_GNUC_PREREQ(2, 95, 0))
+
+# define V8_HAS_ATTRIBUTE_ALIGNED (V8_GNUC_PREREQ(2, 95, 0))
// always_inline is available in gcc 4.0 but not very reliable until 4.4.
// Works around "sorry, unimplemented: inlining failed" build errors with
// older compilers.
@@ -164,6 +175,7 @@
// both for forward compatibility.
# if defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L
# define V8_HAS_CXX11_ALIGNAS (V8_GNUC_PREREQ(4, 8, 0))
+# define V8_HAS_CXX11_ALIGNOF (V8_GNUC_PREREQ(4, 5, 0))
# define V8_HAS_CXX11_STATIC_ASSERT (V8_GNUC_PREREQ(4, 3, 0))
# define V8_HAS_CXX11_DELETE (V8_GNUC_PREREQ(4, 4, 0))
# define V8_HAS_CXX11_OVERRIDE (V8_GNUC_PREREQ(4, 7, 0))
@@ -188,6 +200,7 @@
# define V8_HAS_DECLSPEC_ALIGN 1
# define V8_HAS_DECLSPEC_DEPRECATED (_MSC_VER >= 1300)
+# define V8_HAS___ALIGNOF 1
# define V8_HAS___FORCEINLINE 1
#endif
@@ -279,12 +292,28 @@
// V8_ALIGNAS(32) int array[42];
#if V8_HAS_CXX11_ALIGNAS
# define V8_ALIGNAS(n) alignas(n)
-#elif V8_HAS_ATTRIBUTE___ALIGNED__
-# define V8_ALIGNAS(n) __attribute__((__aligned__(n)))
+#elif V8_HAS_ATTRIBUTE_ALIGNED
+# define V8_ALIGNAS(n) __attribute__((aligned(n)))
#elif V8_HAS_DECLSPEC_ALIGN
# define V8_ALIGNAS(n) __declspec(align(n))
#else
# define V8_ALIGNAS(n) /* NOT SUPPORTED */
#endif
+// This macro takes a type and returns the power of 2 byte boundary on
which
+// the type instances must be allocated.
+// Use like:
+// size_t alignment = V8_ALIGNOF(double);
+// V8_ALIGNAS(V8_ALIGNOF(void*)) int x;
+#if V8_HAS_CXX11_ALIGNOF
+# define V8_ALIGNOF(t) alignof(t)
+#elif V8_HAS___ALIGNOF
+# define V8_ALIGNOF(t) __alignof(t)
+#elif V8_HAS___ALIGNOF__
+# define V8_ALIGNOF(t) __alignof__(t)
+#else
+namespace v8 { template <typename T> struct AlignOfHelper { char x; T t;
}; }
+# define V8_ALIGNOF(t) (sizeof(::v8::AlignOfHelper<t>) - sizeof(t))
+#endif
+
#endif // V8CONFIG_H_
Index: src/lazy-instance.h
diff --git a/src/lazy-instance.h b/src/lazy-instance.h
index
9d68b8cacce0f0f4815f6a5940716df0ddf83bbb..cdde2255ff19be0ef92c00f40916249769449665
100644
--- a/src/lazy-instance.h
+++ b/src/lazy-instance.h
@@ -111,17 +111,9 @@ struct LeakyInstanceTrait {
// Traits that define how an instance is allocated and accessed.
-// TODO(kalmard): __alignof__ is only defined for GCC > 4.2. Fix alignment
issue
-// on MIPS with other compilers.
-#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__
2))
-#define LAZY_ALIGN(x) __attribute__((aligned(__alignof__(x))))
-#else
-#define LAZY_ALIGN(x)
-#endif
-
template <typename T>
struct StaticallyAllocatedInstanceTrait {
- typedef char StorageType[sizeof(T)] LAZY_ALIGN(T);
+ typedef char StorageType[sizeof(T)] V8_ALIGNAS(V8_ALIGNOF(T));
static T* MutableInstance(StorageType* storage) {
return reinterpret_cast<T*>(storage);
@@ -133,8 +125,6 @@ struct StaticallyAllocatedInstanceTrait {
}
};
-#undef LAZY_ALIGN
-
template <typename T>
struct DynamicallyAllocatedInstanceTrait {
--
--
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