[PATCH v7 27/39] mempool: use C11 alignas

[Tyler Retzlaff <roretzla@linux.microsoft.com>]

The current location used for __rte_aligned(a) for alignment of types
and variables is not compatible with MSVC. There is only a single
location accepted by both toolchains.

For variables standard C11 offers alignas(a) supported by conformant
compilers i.e. both MSVC and GCC.

For types the standard offers no alignment facility that compatibly
interoperates with C and C++ but may be achieved by relocating the
placement of __rte_aligned(a) to the aforementioned location accepted
by all currently supported toolchains.

To allow alignment for both compilers do the following:

* Move __rte_aligned from the end of {struct,union} definitions to
  be between {struct,union} and tag.

  The placement between {struct,union} and the tag allows the desired
  alignment to be imparted on the type regardless of the toolchain being
  used for all of GCC, LLVM, MSVC compilers building both C and C++.

* Replace use of __rte_aligned(a) on variables/fields with alignas(a).

Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
Acked-by: Morten Brørup <mb@smartsharesystems.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@huawei.com>
---
 lib/mempool/rte_mempool.h | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/lib/mempool/rte_mempool.h b/lib/mempool/rte_mempool.h
index 6fa4d48..23fd5c8 100644
--- a/lib/mempool/rte_mempool.h
+++ b/lib/mempool/rte_mempool.h
@@ -34,6 +34,7 @@
  * user cache created with rte_mempool_cache_create().
  */
 
+#include <stdalign.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <inttypes.h>
@@ -66,7 +67,7 @@
  * captured since they can be calculated from other stats.
  * For example: put_cache_objs = put_objs - put_common_pool_objs.
  */
-struct rte_mempool_debug_stats {
+struct __rte_cache_aligned rte_mempool_debug_stats {
 	uint64_t put_bulk;             /**< Number of puts. */
 	uint64_t put_objs;             /**< Number of objects successfully put. */
 	uint64_t put_common_pool_bulk; /**< Number of bulks enqueued in common pool. */
@@ -80,13 +81,13 @@ struct rte_mempool_debug_stats {
 	uint64_t get_success_blks;     /**< Successful allocation number of contiguous blocks. */
 	uint64_t get_fail_blks;        /**< Failed allocation number of contiguous blocks. */
 	RTE_CACHE_GUARD;
-} __rte_cache_aligned;
+};
 #endif
 
 /**
  * A structure that stores a per-core object cache.
  */
-struct rte_mempool_cache {
+struct __rte_cache_aligned rte_mempool_cache {
 	uint32_t size;	      /**< Size of the cache */
 	uint32_t flushthresh; /**< Threshold before we flush excess elements */
 	uint32_t len;	      /**< Current cache count */
@@ -109,8 +110,8 @@ struct rte_mempool_cache {
 	 * Cache is allocated to this size to allow it to overflow in certain
 	 * cases to avoid needless emptying of cache.
 	 */
-	void *objs[RTE_MEMPOOL_CACHE_MAX_SIZE * 2] __rte_cache_aligned;
-} __rte_cache_aligned;
+	alignas(RTE_CACHE_LINE_SIZE) void *objs[RTE_MEMPOOL_CACHE_MAX_SIZE * 2];
+};
 
 /**
  * A structure that stores the size of mempool elements.
@@ -218,15 +219,15 @@ struct rte_mempool_memhdr {
  * The structure is cache-line aligned to avoid ABI breakages in
  * a number of cases when something small is added.
  */
-struct rte_mempool_info {
+struct __rte_cache_aligned rte_mempool_info {
 	/** Number of objects in the contiguous block */
 	unsigned int contig_block_size;
-} __rte_cache_aligned;
+};
 
 /**
  * The RTE mempool structure.
  */
-struct rte_mempool {
+struct __rte_cache_aligned rte_mempool {
 	char name[RTE_MEMPOOL_NAMESIZE]; /**< Name of mempool. */
 	union {
 		void *pool_data;         /**< Ring or pool to store objects. */
@@ -268,7 +269,7 @@ struct rte_mempool {
 	 */
 	struct rte_mempool_debug_stats stats[RTE_MAX_LCORE + 1];
 #endif
-}  __rte_cache_aligned;
+};
 
 /** Spreading among memory channels not required. */
 #define RTE_MEMPOOL_F_NO_SPREAD		0x0001
@@ -688,7 +689,7 @@ typedef int (*rte_mempool_get_info_t)(const struct rte_mempool *mp,
 
 
 /** Structure defining mempool operations structure */
-struct rte_mempool_ops {
+struct __rte_cache_aligned rte_mempool_ops {
 	char name[RTE_MEMPOOL_OPS_NAMESIZE]; /**< Name of mempool ops struct. */
 	rte_mempool_alloc_t alloc;       /**< Allocate private data. */
 	rte_mempool_free_t free;         /**< Free the external pool. */
@@ -713,7 +714,7 @@ struct rte_mempool_ops {
 	 * Dequeue a number of contiguous object blocks.
 	 */
 	rte_mempool_dequeue_contig_blocks_t dequeue_contig_blocks;
-} __rte_cache_aligned;
+};
 
 #define RTE_MEMPOOL_MAX_OPS_IDX 16  /**< Max registered ops structs */
 
@@ -726,14 +727,14 @@ struct rte_mempool_ops {
  * any function pointers stored directly in the mempool struct would not be.
  * This results in us simply having "ops_index" in the mempool struct.
  */
-struct rte_mempool_ops_table {
+struct __rte_cache_aligned rte_mempool_ops_table {
 	rte_spinlock_t sl;     /**< Spinlock for add/delete. */
 	uint32_t num_ops;      /**< Number of used ops structs in the table. */
 	/**
 	 * Storage for all possible ops structs.
 	 */
 	struct rte_mempool_ops ops[RTE_MEMPOOL_MAX_OPS_IDX];
-} __rte_cache_aligned;
+};
 
 /** Array of registered ops structs. */
 extern struct rte_mempool_ops_table rte_mempool_ops_table;
-- 
1.8.3.1