[dpdk-dev,v6,5/7] hash: add fallback to software CRC32 implementation
Commit Message
Initially, SSE4.2 support is detected via the constructor function.
Added rte_hash_crc_set_alg() function to detect and set CRC32
implementation if necessary. SSE4.2 is allowed by default.
rte_hash_crc_*byte() functions reworked so they choose available
CRC32 implementation in the runtime.
Signed-off-by: Yerden Zhumabekov <e_zhumabekov@sts.kz>
---
lib/librte_hash/rte_hash_crc.h | 61 ++++++++++++++++++++++++++++++++++++++--
1 file changed, 59 insertions(+), 2 deletions(-)
@@ -45,6 +45,8 @@ extern "C" {
#endif
#include <stdint.h>
+#include <rte_cpuflags.h>
+#include <rte_branch_prediction.h>
/* Lookup tables for software implementation of CRC32C */
static const uint32_t crc32c_tables[8][256] = {{
@@ -396,8 +398,52 @@ crc32c_sse42_u64_mimic(uint64_t data, uint64_t init_val)
return init_val;
}
+#define CRC32_SW (1U << 0)
+#define CRC32_SSE42 (1U << 1)
+#define CRC32_x64 (1U << 2)
+#define CRC32_SSE42_x64 (CRC32_x64|CRC32_SSE42)
+
+static uint8_t crc32_alg = CRC32_SW;
+
+/**
+ * Allow or disallow use of SSE4.2 instrinsics for CRC32 hash
+ * calculation.
+ *
+ * @param flag
+ * An OR of following flags:
+ * - (CRC32_SW) Don't use SSE4.2 intrinsics
+ * - (CRC32_SSE42) Use SSE4.2 intrinsics if available
+ * - (CRC32_SSE42_x64) Use 64-bit SSE4.2 intrinsic if available (default)
+ *
+ */
+static inline void
+rte_hash_crc_set_alg(uint8_t alg)
+{
+ switch (alg) {
+ case CRC32_SSE42_x64:
+ if (! rte_cpu_get_flag_enabled(RTE_CPUFLAG_EM64T))
+ alg = CRC32_SSE42;
+ case CRC32_SSE42:
+ if (! rte_cpu_get_flag_enabled(RTE_CPUFLAG_SSE4_2))
+ alg = CRC32_SW;
+ case CRC32_SW:
+ crc32_alg = alg;
+ default:
+ break;
+ }
+}
+
+/* Setting the best available algorithm */
+static inline void __attribute__((constructor))
+rte_hash_crc_init_alg(void)
+{
+ rte_hash_crc_set_alg(CRC32_SSE42_x64);
+}
+
/**
* Use single crc32 instruction to perform a hash on a 4 byte value.
+ * Fall back to software crc32 implementation in case SSE4.2 is
+ * not supported
*
* @param data
* Data to perform hash on.
@@ -409,11 +455,16 @@ crc32c_sse42_u64_mimic(uint64_t data, uint64_t init_val)
static inline uint32_t
rte_hash_crc_4byte(uint32_t data, uint32_t init_val)
{
- return crc32c_sse42_u32(data, init_val);
+ if (likely(crc32_alg & CRC32_SSE42))
+ return crc32c_sse42_u32(data, init_val);
+
+ return crc32c_1word(data, init_val);
}
/**
* Use single crc32 instruction to perform a hash on a 8 byte value.
+ * Fall back to software crc32 implementation in case SSE4.2 is
+ * not supported
*
* @param data
* Data to perform hash on.
@@ -425,7 +476,13 @@ rte_hash_crc_4byte(uint32_t data, uint32_t init_val)
static inline uint32_t
rte_hash_crc_8byte(uint64_t data, uint32_t init_val)
{
- return crc32c_sse42_u64(data, init_val);
+ if (likely(crc32_alg == CRC32_SSE42_x64))
+ return crc32c_sse42_u64(data, init_val);
+
+ if (likely(crc32_alg & CRC32_SSE42))
+ return crc32c_sse42_u64_mimic(data, init_val);
+
+ return crc32c_2words(data, init_val);
}
/**