From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yerden Zhumabekov Subject: [PATCH] hash: fix breaking strict-aliasing rules Date: Wed, 18 Mar 2015 22:51:12 +0600 Message-ID: Mime-Version: 1.0 Content-Type: text/plain To: Return-path: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" Fix rte_hash_crc() function. Casting uint64_t pointer to uin32_t may trigger a compiler warning about breaking strict-aliasing rules. To avoid that, introduce a lookup table which is used to mask out a remainder of data. See issue #1, http://dpdk.org/ml/archives/dev/2015-March/015174.html Signed-off-by: Yerden Zhumabekov --- lib/librte_hash/rte_hash_crc.h | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-) diff --git a/lib/librte_hash/rte_hash_crc.h b/lib/librte_hash/rte_hash_crc.h index 3dcd362..e81920f 100644 --- a/lib/librte_hash/rte_hash_crc.h +++ b/lib/librte_hash/rte_hash_crc.h @@ -323,6 +323,16 @@ static const uint32_t crc32c_tables[8][256] = {{ 0xE54C35A1, 0xAC704886, 0x7734CFEF, 0x3E08B2C8, 0xC451B7CC, 0x8D6DCAEB, 0x56294D82, 0x1F1530A5 }}; +static const uint64_t odd_8byte_mask[] = { + 0x00FFFFFFFFFFFFFF, + 0x0000FFFFFFFFFFFF, + 0x000000FFFFFFFFFF, + 0x00000000FFFFFFFF, + 0x0000000000FFFFFF, + 0x000000000000FFFF, + 0x00000000000000FF, +}; + #define CRC32_UPD(crc, n) \ (crc32c_tables[(n)][(crc) & 0xFF] ^ \ crc32c_tables[(n)-1][((crc) >> 8) & 0xFF]) @@ -535,38 +545,27 @@ static inline uint32_t rte_hash_crc(const void *data, uint32_t data_len, uint32_t init_val) { unsigned i; - uint64_t temp = 0; + uint64_t temp; const uint64_t *p64 = (const uint64_t *)data; for (i = 0; i < data_len / 8; i++) { init_val = rte_hash_crc_8byte(*p64++, init_val); } - switch (7 - (data_len & 0x07)) { + i = 7 - (data_len & 0x07); + switch (i) { case 0: - temp |= (uint64_t) *((const uint8_t *)p64 + 6) << 48; - /* Fallthrough */ case 1: - temp |= (uint64_t) *((const uint8_t *)p64 + 5) << 40; - /* Fallthrough */ case 2: - temp |= (uint64_t) *((const uint8_t *)p64 + 4) << 32; - temp |= *((const uint32_t *)p64); + temp = odd_8byte_mask[i] & *p64; init_val = rte_hash_crc_8byte(temp, init_val); break; case 3: - init_val = rte_hash_crc_4byte(*(const uint32_t *)p64, init_val); - break; case 4: - temp |= *((const uint8_t *)p64 + 2) << 16; - /* Fallthrough */ case 5: - temp |= *((const uint8_t *)p64 + 1) << 8; - /* Fallthrough */ case 6: - temp |= *((const uint8_t *)p64); + temp = odd_8byte_mask[i] & *p64; init_val = rte_hash_crc_4byte(temp, init_val); - /* Fallthrough */ default: break; } -- 1.7.9.5