[PATCH v5 4/7] hash: simplify key comparison across architectures

Stephen Hemminger
2026-01-30T20:23:58Z

Refactor hash key comparison functions to reduce code duplication
and improve portability:

- Keep optimized 16-byte and 32-byte comparisons for x86 (SSE) and
ARM64 (NEON), but remove the larger size-specific functions (48,
64, 80, 96, 112, 128 bytes) from the architecture headers
- Add generic implementation using XOR for platforms without SIMD
- Move larger key comparison functions into rte_cuckoo_hash.c where
they build upon the 16-byte primitives
- Enable optimized key comparisons on all architectures, not just
x86 and ARM64

The rte_hash_k32_cmp_eq() function remains exposed because it is
used internally by the IP fragmentation library.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
lib/hash/rte_cmp_arm64.h | 62 +++------------------------
lib/hash/rte_cmp_generic.h | 35 ++++++++++++++++
lib/hash/rte_cmp_x86.h | 62 +++------------------------
lib/hash/rte_cuckoo_hash.c | 86 +++++++++++++++++++++++++++++++++-----
4 files changed, 120 insertions(+), 125 deletions(-)
create mode 100644 lib/hash/rte_cmp_generic.h

diff --git a/lib/hash/rte_cmp_arm64.h b/lib/hash/rte_cmp_arm64.h
index a3e85635eb..f209aaf474 100644
--- a/lib/hash/rte_cmp_arm64.h
+++ b/lib/hash/rte_cmp_arm64.h
@@ -2,7 +2,7 @@
* Copyright(c) 2015 Cavium, Inc
*/

-/* Functions to compare multiple of 16 byte keys (up to 128 bytes) */
+/* Functions to compare multiple of 16 byte keys */
static inline int
rte_hash_k16_cmp_eq(const void *key1, const void *key2,
size_t key_len __rte_unused)
@@ -25,61 +25,9 @@ rte_hash_k16_cmp_eq(const void *key1, const void *key2,
}

static inline int
-rte_hash_k32_cmp_eq(const void *key1, const void *key2, size_t key_len)
+rte_hash_k32_cmp_eq(const void *key1, const void *key2, size_t key_len __rte_unused)
{
- return rte_hash_k16_cmp_eq(key1, key2, key_len) ||
- rte_hash_k16_cmp_eq((const char *) key1 + 16,
- (const char *) key2 + 16, key_len);
-}
-
-static inline int
-rte_hash_k48_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k16_cmp_eq(key1, key2, key_len) ||
- rte_hash_k16_cmp_eq((const char *) key1 + 16,
- (const char *) key2 + 16, key_len) ||
- rte_hash_k16_cmp_eq((const char *) key1 + 32,
- (const char *) key2 + 32, key_len);
-}
-
-static inline int
-rte_hash_k64_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k32_cmp_eq(key1, key2, key_len) ||
- rte_hash_k32_cmp_eq((const char *) key1 + 32,
- (const char *) key2 + 32, key_len);
-}
-
-static inline int
-rte_hash_k80_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k64_cmp_eq(key1, key2, key_len) ||
- rte_hash_k16_cmp_eq((const char *) key1 + 64,
- (const char *) key2 + 64, key_len);
-}
-
-static inline int
-rte_hash_k96_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k64_cmp_eq(key1, key2, key_len) ||
- rte_hash_k32_cmp_eq((const char *) key1 + 64,
- (const char *) key2 + 64, key_len);
-}
-
-static inline int
-rte_hash_k112_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k64_cmp_eq(key1, key2, key_len) ||
- rte_hash_k32_cmp_eq((const char *) key1 + 64,
- (const char *) key2 + 64, key_len) ||
- rte_hash_k16_cmp_eq((const char *) key1 + 96,
- (const char *) key2 + 96, key_len);
-}
-
-static inline int
-rte_hash_k128_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k64_cmp_eq(key1, key2, key_len) ||
- rte_hash_k64_cmp_eq((const char *) key1 + 64,
- (const char *) key2 + 64, key_len);
+ return rte_hash_k16_cmp_eq(key1, key2, 16) |
+ rte_hash_k16_cmp_eq((const uint8_t *)key1 + 16,
+ (const uint8_t *)key2 + 16, 16);
}
diff --git a/lib/hash/rte_cmp_generic.h b/lib/hash/rte_cmp_generic.h
new file mode 100644
index 0000000000..771180e97a
--- /dev/null
+++ b/lib/hash/rte_cmp_generic.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2026 Stephen Hemminger
+ */
+
+#ifndef _RTE_CMP_GENERIC_H_
+#define _RTE_CMP_GENERIC_H_
+
+/* Function to compare 16 byte keys */
+static inline int
+rte_hash_k16_cmp_eq(const void *key1, const void *key2, size_t key_len __rte_unused)
+{
+#ifdef RTE_ARCH_64
+ const unaligned_uint64_t *k1 = key1;
+ const unaligned_uint64_t *k2 = key2;
+
+ return !!((k1[0] ^ k2[0]) | (k1[1] ^ k2[1]));
+#else
+ const unaligned_uint32_t *k1 = key1;
+ const unaligned_uint32_t *k2 = key2;
+
+ return !!((k1[0] ^ k2[0]) | (k1[1] ^ k2[1]) |
+ (k1[2] ^ k2[2]) | (k1[3] ^ k2[3]));
+#endif
+}
+
+/* Function to compare 32 byte keys */
+static inline int
+rte_hash_k32_cmp_eq(const void *key1, const void *key2, size_t key_len)
+{
+ return rte_hash_k16_cmp_eq(key1, key2, key_len) |
+ rte_hash_k16_cmp_eq((const uint8_t *) key1 + 16,
+ (const uint8_t *) key2 + 16, key_len);
+}
+
+#endif /* _RTE_CMP_GENERIC_H_ */
diff --git a/lib/hash/rte_cmp_x86.h b/lib/hash/rte_cmp_x86.h
index ddfbef462f..b450150d6d 100644
--- a/lib/hash/rte_cmp_x86.h
+++ b/lib/hash/rte_cmp_x86.h
@@ -4,7 +4,7 @@

#include <rte_vect.h>

-/* Functions to compare multiple of 16 byte keys (up to 128 bytes) */
+/* Function to compare multiple of 16 byte keys */
static inline int
rte_hash_k16_cmp_eq(const void *key1, const void *key2, size_t key_len __rte_unused)
{
@@ -16,61 +16,9 @@ rte_hash_k16_cmp_eq(const void *key1, const void *key2, size_t key_len __rte_unu
}

static inline int
-rte_hash_k32_cmp_eq(const void *key1, const void *key2, size_t key_len)
+rte_hash_k32_cmp_eq(const void *key1, const void *key2, size_t key_len __rte_unused)
{
- return rte_hash_k16_cmp_eq(key1, key2, key_len) ||
- rte_hash_k16_cmp_eq((const char *) key1 + 16,
- (const char *) key2 + 16, key_len);
-}
-
-static inline int
-rte_hash_k48_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k16_cmp_eq(key1, key2, key_len) ||
- rte_hash_k16_cmp_eq((const char *) key1 + 16,
- (const char *) key2 + 16, key_len) ||
- rte_hash_k16_cmp_eq((const char *) key1 + 32,
- (const char *) key2 + 32, key_len);
-}
-
-static inline int
-rte_hash_k64_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k32_cmp_eq(key1, key2, key_len) ||
- rte_hash_k32_cmp_eq((const char *) key1 + 32,
- (const char *) key2 + 32, key_len);
-}
-
-static inline int
-rte_hash_k80_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k64_cmp_eq(key1, key2, key_len) ||
- rte_hash_k16_cmp_eq((const char *) key1 + 64,
- (const char *) key2 + 64, key_len);
-}
-
-static inline int
-rte_hash_k96_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k64_cmp_eq(key1, key2, key_len) ||
- rte_hash_k32_cmp_eq((const char *) key1 + 64,
- (const char *) key2 + 64, key_len);
-}
-
-static inline int
-rte_hash_k112_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k64_cmp_eq(key1, key2, key_len) ||
- rte_hash_k32_cmp_eq((const char *) key1 + 64,
- (const char *) key2 + 64, key_len) ||
- rte_hash_k16_cmp_eq((const char *) key1 + 96,
- (const char *) key2 + 96, key_len);
-}
-
-static inline int
-rte_hash_k128_cmp_eq(const void *key1, const void *key2, size_t key_len)
-{
- return rte_hash_k64_cmp_eq(key1, key2, key_len) ||
- rte_hash_k64_cmp_eq((const char *) key1 + 64,
- (const char *) key2 + 64, key_len);
+ return rte_hash_k16_cmp_eq(key1, key2, 16) |
+ rte_hash_k16_cmp_eq((const uint8_t *) key1 + 16,
+ (const uint8_t *) key2 + 16, 16);
}
diff --git a/lib/hash/rte_cuckoo_hash.c b/lib/hash/rte_cuckoo_hash.c
index 619fe0c691..ce66308c5e 100644
--- a/lib/hash/rte_cuckoo_hash.c
+++ b/lib/hash/rte_cuckoo_hash.c
@@ -42,13 +42,6 @@ RTE_LOG_REGISTER_DEFAULT(hash_logtype, INFO);
#define RETURN_IF_TRUE(cond, retval)
#endif

-#if defined(RTE_ARCH_X86)
-#include "rte_cmp_x86.h"
-#endif
-
-#if defined(RTE_ARCH_ARM64)
-#include "rte_cmp_arm64.h"
-#endif

/*
* All different options to select a key compare function,
@@ -57,7 +50,6 @@ RTE_LOG_REGISTER_DEFAULT(hash_logtype, INFO);
*/
enum cmp_jump_table_case {
KEY_CUSTOM = 0,
-#if defined(RTE_ARCH_X86) || defined(RTE_ARCH_ARM64)
KEY_16_BYTES,
KEY_32_BYTES,
KEY_48_BYTES,
@@ -66,11 +58,85 @@ enum cmp_jump_table_case {
KEY_96_BYTES,
KEY_112_BYTES,
KEY_128_BYTES,
-#endif
KEY_OTHER_BYTES,
NUM_KEY_CMP_CASES,
};

+/*
+ * Comparison functions for different key sizes.
+ * Each function is only called with a specific fixed key size.
+ *
+ * Return value is 0 on equality to allow direct use of memcmp.
+ * Recommend using XOR and | operator to avoid branching
+ * as long as key is smaller than cache line size.
+ *
+ * Key1 always points to key[] in rte_hash_key which is aligned.
+ * Key2 is parameter to insert which might not be.
+ *
+ * Special cases for 16 and 32 bytes to allow for architecture
+ * specific optimizations.
+ */
+
+#if defined(RTE_ARCH_X86)
+#include "rte_cmp_x86.h"
+#elif defined(RTE_ARCH_ARM64)
+#include "rte_cmp_arm64.h"
+#else
+#include "rte_cmp_generic.h"
+#endif
+
+static int
+rte_hash_k48_cmp_eq(const void *key1, const void *key2, size_t key_len)
+{
+ return rte_hash_k16_cmp_eq(key1, key2, key_len) |
+ rte_hash_k16_cmp_eq((const uint8_t *) key1 + 16,
+ (const uint8_t *) key2 + 16, key_len) |
+ rte_hash_k16_cmp_eq((const uint8_t *) key1 + 32,
+ (const uint8_t *) key2 + 32, key_len);
+}
+
+static int
+rte_hash_k64_cmp_eq(const void *key1, const void *key2, size_t key_len)
+{
+ return rte_hash_k32_cmp_eq(key1, key2, key_len) |
+ rte_hash_k32_cmp_eq((const uint8_t *) key1 + 32,
+ (const uint8_t *) key2 + 32, key_len);
+}
+
+static int
+rte_hash_k80_cmp_eq(const void *key1, const void *key2, size_t key_len)
+{
+ return rte_hash_k64_cmp_eq(key1, key2, key_len) |
+ rte_hash_k16_cmp_eq((const uint8_t *) key1 + 64,
+ (const uint8_t *) key2 + 64, key_len);
+}
+
+static int
+rte_hash_k96_cmp_eq(const void *key1, const void *key2, size_t key_len)
+{
+ return rte_hash_k64_cmp_eq(key1, key2, key_len) |
+ rte_hash_k32_cmp_eq((const uint8_t *) key1 + 64,
+ (const uint8_t *) key2 + 64, key_len);
+}
+
+static int
+rte_hash_k112_cmp_eq(const void *key1, const void *key2, size_t key_len)
+{
+ return rte_hash_k64_cmp_eq(key1, key2, key_len) |
+ rte_hash_k32_cmp_eq((const uint8_t *) key1 + 64,
+ (const uint8_t *) key2 + 64, key_len) |
+ rte_hash_k16_cmp_eq((const uint8_t *) key1 + 96,
+ (const uint8_t *) key2 + 96, key_len);
+}
+
+static int
+rte_hash_k128_cmp_eq(const void *key1, const void *key2, size_t key_len)
+{
+ return rte_hash_k64_cmp_eq(key1, key2, key_len) |
+ rte_hash_k64_cmp_eq((const uint8_t *) key1 + 64,
+ (const uint8_t *) key2 + 64, key_len);
+}
+
/* Enum used to select the implementation of the signature comparison function to use
* eg: a system supporting SVE might want to use a NEON or scalar implementation.
*/
@@ -160,7 +226,6 @@ void rte_hash_set_cmp_func(struct rte_hash *h, rte_hash_cmp_eq_t func)
*/
static const rte_hash_cmp_eq_t cmp_jump_table[NUM_KEY_CMP_CASES] = {
[KEY_CUSTOM] = NULL,
-#if defined(RTE_ARCH_X86) || defined(RTE_ARCH_ARM64)
[KEY_16_BYTES] = rte_hash_k16_cmp_eq,
[KEY_32_BYTES] = rte_hash_k32_cmp_eq,
[KEY_48_BYTES] = rte_hash_k48_cmp_eq,
@@ -169,7 +234,6 @@ static const rte_hash_cmp_eq_t cmp_jump_table[NUM_KEY_CMP_CASES] = {
[KEY_96_BYTES] = rte_hash_k96_cmp_eq,
[KEY_112_BYTES] = rte_hash_k112_cmp_eq,
[KEY_128_BYTES] = rte_hash_k128_cmp_eq,
-#endif
[KEY_OTHER_BYTES] = memcmp,
};

--
2.51.0