commit ed0832b66b44d3d6367c1e51d83ccea8a8a5d506
author Willy Tarreau <w@1wt.eu> Sat Feb 22 15:51:39 2020 +0100
committer Christopher Faulet <cfaulet@haproxy.com> Fri Feb 28 11:24:45 2020 +0100
tree 7776ff57f3428e6a883ae5a23896d83af7d3395a
parent 52d0ed904f97b85d846416ae9cb20798b7452770

MINOR: compiler: add new alignment macros

This commit adds ALWAYS_ALIGN(), MAYBE_ALIGN() and ATOMIC_ALIGN() to
be placed as delimitors inside structures to force alignment to a
given size. These depend on the architecture's capabilities so that
it is possible to always align, align only on archs not supporting
unaligned accesses at all, or only on those not supporting them for
atomic accesses (e.g. before a lock).

(cherry picked from commit 226ef26056d9e6151c9838e70a3e2f4db5068cd8)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 8959ef33693442bfe9256e0c07a5768a86c4ab5d)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>

include/common/compiler.h

diff --git a/include/common/compiler.h b/include/common/compiler.h
index 179b318..e5fcf38 100644
--- a/include/common/compiler.h
+++ b/include/common/compiler.h
@@ -183,4 +183,55 @@
 #define HA_HAVE_CAS_DW
 #endif
 
+
+/* sets alignment for current field or variable */
+#ifndef ALIGNED
+#define ALIGNED(x) __attribute__((aligned(x)))
+#endif
+
+/* sets alignment only on architectures preventing unaligned atomic accesses */
+#ifndef MAYBE_ALIGNED
+#ifndef HA_UNALIGNED
+#define MAYBE_ALIGNED(x)  ALIGNED(x)
+#else
+#define MAYBE_ALIGNED(x)
+#endif
+#endif
+
+/* sets alignment only on architectures preventing unaligned atomic accesses */
+#ifndef ATOMIC_ALIGNED
+#ifndef HA_UNALIGNED_ATOMIC
+#define ATOMIC_ALIGNED(x)  ALIGNED(x)
+#else
+#define ATOMIC_ALIGNED(x)
+#endif
+#endif
+
+/* add a mandatory alignment for next fields in a structure */
+#ifndef ALWAYS_ALIGN
+#define ALWAYS_ALIGN(x)  union { } ALIGNED(x)
+#endif
+
+/* add an optional alignment for next fields in a structure, only for archs
+ * which do not support unaligned accesses.
+ */
+#ifndef MAYBE_ALIGN
+#ifndef HA_UNALIGNED
+#define MAYBE_ALIGN(x)  union { } ALIGNED(x)
+#else
+#define MAYBE_ALIGN(x)
+#endif
+#endif
+
+/* add an optional alignment for next fields in a structure, only for archs
+ * which do not support unaligned accesses for atomic operations.
+ */
+#ifndef ATOMIC_ALIGN
+#ifndef HA_UNALIGNED_ATOMIC
+#define ATOMIC_ALIGN(x)  union { } ALIGNED(x)
+#else
+#define ATOMIC_ALIGN(x)
+#endif
+#endif
+
 #endif /* _COMMON_COMPILER_H */