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authorGravatar Abseil Team <absl-team@google.com>2018-12-27 02:49:35 -0800
committerGravatar Gennadiy Civil <misterg@google.com>2018-12-27 11:50:39 -0500
commit7ffbe09f3d85504bd018783bbe1e2c12992fe47c (patch)
treef91fa25267d411ba91edbb8c447e9fdc2bd91881
parent01b471d9f3ebef27f5aaca14b66509099fa8cd6c (diff)
Export of internal Abseil changes.
-- 027adbb0bceda5c3908f7f4d3a911284ee407b3d by Abseil Team <absl-team@google.com>: Make ABSL_CACHELINE_ALIGNED work for Visual C++. PiperOrigin-RevId: 227007205 GitOrigin-RevId: 027adbb0bceda5c3908f7f4d3a911284ee407b3d Change-Id: I572ec7e79dda1291eb324c90a39be90e744b4b05
-rw-r--r--absl/base/optimization.h20
1 files changed, 15 insertions, 5 deletions
diff --git a/absl/base/optimization.h b/absl/base/optimization.h
index 2fddfc8..9789c2c 100644
--- a/absl/base/optimization.h
+++ b/absl/base/optimization.h
@@ -111,9 +111,9 @@
// See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0154r1.html
// for more information.
//
-// On some compilers, `ABSL_CACHELINE_ALIGNED` expands to
-// `__attribute__((aligned(ABSL_CACHELINE_SIZE)))`. For compilers where this is
-// not known to work, the macro expands to nothing.
+// On some compilers, `ABSL_CACHELINE_ALIGNED` expands to an `__attribute__`
+// or `__declspec` attribute. For compilers where this is not known to work,
+// the macro expands to nothing.
//
// No further guarantees are made here. The result of applying the macro
// to variables and types is always implementation-defined.
@@ -122,6 +122,14 @@
// of causing bugs that are difficult to diagnose, crash, etc. It does not
// of itself guarantee that objects are aligned to a cache line.
//
+// NOTE: Some compilers are picky about the locations of annotations such as
+// this attribute, so prefer to put it at the beginning of your declaration.
+// For example,
+//
+// ABSL_CACHELINE_ALIGNED static Foo* foo = ...
+//
+// class ABSL_CACHELINE_ALIGNED Bar { ...
+//
// Recommendations:
//
// 1) Consult compiler documentation; this comment is not kept in sync as
@@ -131,8 +139,10 @@
// 3) Prefer applying this attribute to individual variables. Avoid
// applying it to types. This tends to localize the effect.
#define ABSL_CACHELINE_ALIGNED __attribute__((aligned(ABSL_CACHELINE_SIZE)))
-
-#else // not GCC
+#elif defined(_MSC_VER)
+#define ABSL_CACHELINE_SIZE 64
+#define ABSL_CACHELINE_ALIGNED __declspec(align(ABSL_CACHELINE_SIZE))
+#else
#define ABSL_CACHELINE_SIZE 64
#define ABSL_CACHELINE_ALIGNED
#endif