[PATCH v6 09/39] hash: 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>
---
 lib/hash/rte_cuckoo_hash.h | 16 +++++++++-------
 lib/hash/rte_thash.c       |  4 +++-
 lib/hash/rte_thash.h       |  8 ++++----
 3 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/lib/hash/rte_cuckoo_hash.h b/lib/hash/rte_cuckoo_hash.h
index 8ea793c..a528f1d 100644
--- a/lib/hash/rte_cuckoo_hash.h
+++ b/lib/hash/rte_cuckoo_hash.h
@@ -11,6 +11,8 @@
 #ifndef _RTE_CUCKOO_HASH_H_
 #define _RTE_CUCKOO_HASH_H_
 
+#include <stdalign.h>
+
 #if defined(RTE_ARCH_X86)
 #include "rte_cmp_x86.h"
 #endif
@@ -117,10 +119,10 @@ enum cmp_jump_table_case {
 
 #define RTE_HASH_TSX_MAX_RETRY  10
 
-struct lcore_cache {
+struct __rte_cache_aligned lcore_cache {
 	unsigned len; /**< Cache len */
 	uint32_t objs[LCORE_CACHE_SIZE]; /**< Cache objects */
-} __rte_cache_aligned;
+};
 
 /* Structure that stores key-value pair */
 struct rte_hash_key {
@@ -141,7 +143,7 @@ enum rte_hash_sig_compare_function {
 };
 
 /** Bucket structure */
-struct rte_hash_bucket {
+struct __rte_cache_aligned rte_hash_bucket {
 	uint16_t sig_current[RTE_HASH_BUCKET_ENTRIES];
 
 	RTE_ATOMIC(uint32_t) key_idx[RTE_HASH_BUCKET_ENTRIES];
@@ -149,10 +151,10 @@ struct rte_hash_bucket {
 	uint8_t flag[RTE_HASH_BUCKET_ENTRIES];
 
 	void *next;
-} __rte_cache_aligned;
+};
 
 /** A hash table structure. */
-struct rte_hash {
+struct __rte_cache_aligned rte_hash {
 	char name[RTE_HASH_NAMESIZE];   /**< Name of the hash. */
 	uint32_t entries;               /**< Total table entries. */
 	uint32_t num_buckets;           /**< Number of buckets in table. */
@@ -170,7 +172,7 @@ struct rte_hash {
 
 	/* Fields used in lookup */
 
-	uint32_t key_len __rte_cache_aligned;
+	alignas(RTE_CACHE_LINE_SIZE) uint32_t key_len;
 	/**< Length of hash key. */
 	uint8_t hw_trans_mem_support;
 	/**< If hardware transactional memory is used. */
@@ -220,7 +222,7 @@ struct rte_hash {
 	uint32_t *ext_bkt_to_free;
 	RTE_ATOMIC(uint32_t) *tbl_chng_cnt;
 	/**< Indicates if the hash table changed from last read. */
-} __rte_cache_aligned;
+};
 
 struct queue_node {
 	struct rte_hash_bucket *bkt; /* Current bucket on the bfs search */
diff --git a/lib/hash/rte_thash.c b/lib/hash/rte_thash.c
index e8de071..6464fd3 100644
--- a/lib/hash/rte_thash.c
+++ b/lib/hash/rte_thash.c
@@ -2,6 +2,8 @@
  * Copyright(c) 2021 Intel Corporation
  */
 
+#include <stdalign.h>
+
 #include <sys/queue.h>
 
 #include <rte_thash.h>
@@ -80,7 +82,7 @@ struct rte_thash_subtuple_helper {
 	uint32_t	tuple_offset;	/** < Offset in bits of the subtuple */
 	uint32_t	tuple_len;	/** < Length in bits of the subtuple */
 	uint32_t	lsb_msk;	/** < (1 << reta_sz_log) - 1 */
-	__extension__ uint32_t	compl_table[0] __rte_cache_aligned;
+	__extension__ alignas(RTE_CACHE_LINE_SIZE) uint32_t	compl_table[0];
 	/** < Complementary table */
 };
 
diff --git a/lib/hash/rte_thash.h b/lib/hash/rte_thash.h
index 2681b1b..30b657e 100644
--- a/lib/hash/rte_thash.h
+++ b/lib/hash/rte_thash.h
@@ -99,14 +99,14 @@ struct rte_ipv6_tuple {
 	};
 };
 
+#ifdef RTE_ARCH_X86
+union __rte_aligned(XMM_SIZE) rte_thash_tuple {
+#else
 union rte_thash_tuple {
+#endif
 	struct rte_ipv4_tuple	v4;
 	struct rte_ipv6_tuple	v6;
-#ifdef RTE_ARCH_X86
-} __rte_aligned(XMM_SIZE);
-#else
 };
-#endif
 
 /**
  * Prepare special converted key to use with rte_softrss_be()
-- 
1.8.3.1