Revision: 16318
Author: [email protected]
Date: Mon Aug 26 11:18:28 2013 UTC
Log: Add V8_ALIGNAS() and V8_ALIGNOF() and use that in lazy-instance.h.
This renames the existing V8_ALIGNAS() to V8_ALIGNED(), and introduces
V8_ALIGNAS(type, alignment) which aligns according to the type and falls
back to aligning according to alignment.
Also use __attribute__((aligned(n))) instead of
__attribute__((__aligned__(n))).
[email protected]
Review URL: https://codereview.chromium.org/22999052
http://code.google.com/p/v8/source/detail?r=16318
Modified:
/branches/bleeding_edge/include/v8config.h
/branches/bleeding_edge/src/circular-queue.h
/branches/bleeding_edge/src/lazy-instance.h
=======================================
--- /branches/bleeding_edge/include/v8config.h Mon Aug 26 08:12:08 2013 UTC
+++ /branches/bleeding_edge/include/v8config.h Mon Aug 26 11:18:28 2013 UTC
@@ -97,6 +97,7 @@
// C++11 feature detection
//
// V8_HAS_CXX11_ALIGNAS - alignas specifier supported
+// V8_HAS_CXX11_ALIGNOF - alignof(type) 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(type) operator supported
+// V8_HAS___ALIGNOF__ - __alignof__(type) 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 +125,11 @@
# define V8_CC_CLANG 1
-# define V8_HAS_ATTRIBUTE___ALIGNED__ (__has_attribute(__aligned__))
+// Clang defines __alignof__ as alias for __alignof
+# define V8_HAS___ALIGNOF 1
+# define V8_HAS___ALIGNOF__ V8_HAS___ALIGNOF
+
+# 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 +153,9 @@
# define V8_CC_MINGW 1
# endif
-# define V8_HAS_ATTRIBUTE___ALIGNED__ (V8_GNUC_PREREQ(2, 95, 0))
+# define V8_HAS___ALIGNOF__ (V8_GNUC_PREREQ(4, 3, 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 +173,7 @@
// 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, 8, 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))
@@ -179,6 +189,8 @@
# define V8_CC_MSVC 1
+# define V8_HAS___ALIGNOF 1
+
// Override control was added with Visual Studio 2005, but
// Visual Studio 2010 and earlier spell "final" as "sealed".
# define V8_HAS_CXX11_FINAL (_MSC_VER >= 1700)
@@ -275,16 +287,54 @@
// This macro allows to specify memory alignment for structs, classes, etc.
// Use like:
-// class V8_ALIGNAS(16) MyClass { ... };
-// V8_ALIGNAS(32) int array[42];
+// class V8_ALIGNED(16) MyClass { ... };
+// V8_ALIGNED(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)))
+# define V8_ALIGNED(n) alignas(n)
+#elif V8_HAS_ATTRIBUTE_ALIGNED
+# define V8_ALIGNED(n) __attribute__((aligned(n)))
#elif V8_HAS_DECLSPEC_ALIGN
-# define V8_ALIGNAS(n) __declspec(align(n))
+# define V8_ALIGNED(n) __declspec(align(n))
#else
-# define V8_ALIGNAS(n) /* NOT SUPPORTED */
+# define V8_ALIGNED(n) /* NOT SUPPORTED */
+#endif
+
+
+// This macro is similar to V8_ALIGNED(), but takes a type instead of size
+// in bytes. If the compiler does not supports using the alignment of the
+// |type|, it will align according to the |alignment| instead. For example,
+// Visual Studio C++ cannot combine __declspec(align) and __alignof. The
+// |alignment| must be a literal that is used as a kind of worst-case
fallback
+// alignment.
+// Use like:
+// struct V8_ALIGNAS(AnotherClass, 16) NewClass { ... };
+// V8_ALIGNAS(double, 8) int array[100];
+#if V8_HAS_CXX11_ALIGNAS
+# define V8_ALIGNAS(type, alignment) alignas(type)
+#elif V8_HAS___ALIGNOF__ && V8_HAS_ATTRIBUTE_ALIGNED
+# define V8_ALIGNAS(type, alignment)
__attribute__((aligned(__alignof__(type))))
+#else
+# define V8_ALIGNAS(type, alignment) V8_ALIGNED(alignment)
+#endif
+
+
+// This macro returns alignment in bytes (an integer power of two)
required for
+// any instance of the given type, which is either complete type, an array
type,
+// or a reference type.
+// Use like:
+// size_t alignment = V8_ALIGNOF(double);
+#if V8_HAS_CXX11_ALIGNOF
+# define V8_ALIGNOF(type) alignof(type)
+#elif V8_HAS___ALIGNOF
+# define V8_ALIGNOF(type) __alignof(type)
+#elif V8_HAS___ALIGNOF__
+# define V8_ALIGNOF(type) __alignof__(type)
+#else
+// Note that alignment of a type within a struct can be less than the
+// alignment of the type stand-alone (because of ancient ABIs), so this
+// should only be used as a last resort.
+namespace v8 { template <typename T> class AlignOfHelper { char c; T t; };
}
+# define V8_ALIGNOF(type) (sizeof(::v8::AlignOfHelper<type>) -
sizeof(type))
#endif
#endif // V8CONFIG_H_
=======================================
--- /branches/bleeding_edge/src/circular-queue.h Fri Aug 23 08:43:57 2013
UTC
+++ /branches/bleeding_edge/src/circular-queue.h Mon Aug 26 11:18:28 2013
UTC
@@ -70,7 +70,7 @@
// completely processed by the consumer.
};
- struct V8_ALIGNAS(PROCESSOR_CACHE_LINE_SIZE) Entry {
+ struct V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry {
Entry() : marker(kEmpty) {}
T record;
Atomic32 marker;
@@ -79,8 +79,8 @@
Entry* Next(Entry* entry);
Entry buffer_[Length];
- V8_ALIGNAS(PROCESSOR_CACHE_LINE_SIZE) Entry* enqueue_pos_;
- V8_ALIGNAS(PROCESSOR_CACHE_LINE_SIZE) Entry* dequeue_pos_;
+ V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry* enqueue_pos_;
+ V8_ALIGNED(PROCESSOR_CACHE_LINE_SIZE) Entry* dequeue_pos_;
DISALLOW_COPY_AND_ASSIGN(SamplingCircularQueue);
};
=======================================
--- /branches/bleeding_edge/src/lazy-instance.h Mon Aug 26 08:12:08 2013 UTC
+++ /branches/bleeding_edge/src/lazy-instance.h Mon Aug 26 11:18:28 2013 UTC
@@ -91,12 +91,13 @@
#ifndef V8_LAZY_INSTANCE_H_
#define V8_LAZY_INSTANCE_H_
+#include "checks.h"
#include "once.h"
namespace v8 {
namespace internal {
-#define LAZY_STATIC_INSTANCE_INITIALIZER { V8_ONCE_INIT, {} }
+#define LAZY_STATIC_INSTANCE_INITIALIZER { V8_ONCE_INIT, { {} } }
#define LAZY_DYNAMIC_INSTANCE_INITIALIZER { V8_ONCE_INIT, 0 }
// Default to static mode.
@@ -111,17 +112,15 @@
// 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);
+ // 16-byte alignment fallback to be on the safe side here.
+ struct V8_ALIGNAS(T, 16) StorageType {
+ char x[sizeof(T)];
+ };
+
+ STATIC_ASSERT(V8_ALIGNOF(StorageType) >= V8_ALIGNOF(T));
static T* MutableInstance(StorageType* storage) {
return reinterpret_cast<T*>(storage);
@@ -133,8 +132,6 @@
}
};
-#undef LAZY_ALIGN
-
template <typename T>
struct DynamicallyAllocatedInstanceTrait {
--
--
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