[PATCH 1/1] lpm: add a scalar version of lookupx4 function

[Stanislaw Kardach <kda@semihalf.com>]

From: Michal Mazurek <maz@semihalf.com>

Add an implementation of the rte_lpm_lookupx4() function for platforms
without support for vector operations.

This will be useful in the upcoming RISC-V port as well as any platform
which may want to start with a basic level of LPM support.

Signed-off-by: Michal Mazurek <maz@semihalf.com>
Signed-off-by: Stanislaw Kardach <kda@semihalf.com>
---
 doc/guides/rel_notes/release_22_07.rst |   5 +
 lib/lpm/meson.build                    |   1 +
 lib/lpm/rte_lpm.h                      |   4 +-
 lib/lpm/rte_lpm_scalar.h               | 122 +++++++++++++++++++++++++
 4 files changed, 131 insertions(+), 1 deletion(-)
 create mode 100644 lib/lpm/rte_lpm_scalar.h

diff --git a/doc/guides/rel_notes/release_22_07.rst b/doc/guides/rel_notes/release_22_07.rst
index 4ae91dd94d..73e8d632f2 100644
--- a/doc/guides/rel_notes/release_22_07.rst
+++ b/doc/guides/rel_notes/release_22_07.rst
@@ -70,6 +70,11 @@ New Features
   * Added AH mode support in lookaside protocol (IPsec) for CN9K & CN10K.
   * Added AES-GMAC support in lookaside protocol (IPsec) for CN9K & CN10K.
 
+* **Added scalar version of the LPM library.**
+
+  * Added scalar implementation of ``rte_lpm_lookupx4``. This is a fall-back
+    implementation for platforms that don't support vector operations.
+
 
 Removed Items
 -------------
diff --git a/lib/lpm/meson.build b/lib/lpm/meson.build
index 78d91d3421..6b47361fce 100644
--- a/lib/lpm/meson.build
+++ b/lib/lpm/meson.build
@@ -14,6 +14,7 @@ headers = files('rte_lpm.h', 'rte_lpm6.h')
 indirect_headers += files(
         'rte_lpm_altivec.h',
         'rte_lpm_neon.h',
+        'rte_lpm_scalar.h',
         'rte_lpm_sse.h',
         'rte_lpm_sve.h',
 )
diff --git a/lib/lpm/rte_lpm.h b/lib/lpm/rte_lpm.h
index eb91960e81..b5db6a353a 100644
--- a/lib/lpm/rte_lpm.h
+++ b/lib/lpm/rte_lpm.h
@@ -405,8 +405,10 @@ rte_lpm_lookupx4(const struct rte_lpm *lpm, xmm_t ip, uint32_t hop[4],
 #endif
 #elif defined(RTE_ARCH_PPC_64)
 #include "rte_lpm_altivec.h"
-#else
+#elif defined(RTE_ARCH_X86)
 #include "rte_lpm_sse.h"
+#else
+#include "rte_lpm_scalar.h"
 #endif
 
 #ifdef __cplusplus
diff --git a/lib/lpm/rte_lpm_scalar.h b/lib/lpm/rte_lpm_scalar.h
new file mode 100644
index 0000000000..991b94e687
--- /dev/null
+++ b/lib/lpm/rte_lpm_scalar.h
@@ -0,0 +1,122 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2022 StarFive
+ * Copyright(c) 2022 SiFive
+ * Copyright(c) 2022 Semihalf
+ */
+
+#ifndef _RTE_LPM_SCALAR_H_
+#define _RTE_LPM_SCALAR_H_
+
+#include <rte_branch_prediction.h>
+#include <rte_byteorder.h>
+#include <rte_common.h>
+#include <rte_vect.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static inline void
+rte_lpm_lookupx4(const struct rte_lpm *lpm, xmm_t ip, uint32_t hop[4],
+		uint32_t defv)
+{
+	rte_xmm_t i24;
+	rte_xmm_t i8;
+	uint32_t tbl[4];
+	uint64_t pt, pt2;
+	const uint32_t *ptbl;
+
+	const rte_xmm_t mask8 = {
+		.u32 = {UINT8_MAX, UINT8_MAX, UINT8_MAX, UINT8_MAX}};
+
+	/*
+	 * RTE_LPM_VALID_EXT_ENTRY_BITMASK for 2 LPM entries
+	 * as one 64-bit value (0x0300000003000000).
+	 */
+	const uint64_t mask_xv =
+		((uint64_t)RTE_LPM_VALID_EXT_ENTRY_BITMASK |
+		(uint64_t)RTE_LPM_VALID_EXT_ENTRY_BITMASK << 32);
+
+	/*
+	 * RTE_LPM_LOOKUP_SUCCESS for 2 LPM entries
+	 * as one 64-bit value (0x0100000001000000).
+	 */
+	const uint64_t mask_v =
+		((uint64_t)RTE_LPM_LOOKUP_SUCCESS |
+		(uint64_t)RTE_LPM_LOOKUP_SUCCESS << 32);
+
+	/* get 4 indexes for tbl24[]. */
+	i24.x = ip;
+	i24.u32[0] >>= CHAR_BIT;
+	i24.u32[1] >>= CHAR_BIT;
+	i24.u32[2] >>= CHAR_BIT;
+	i24.u32[3] >>= CHAR_BIT;
+
+	/* extract values from tbl24[] */
+	ptbl = (const uint32_t *)&lpm->tbl24[i24.u32[0]];
+	tbl[0] = *ptbl;
+	ptbl = (const uint32_t *)&lpm->tbl24[i24.u32[1]];
+	tbl[1] = *ptbl;
+	ptbl = (const uint32_t *)&lpm->tbl24[i24.u32[2]];
+	tbl[2] = *ptbl;
+	ptbl = (const uint32_t *)&lpm->tbl24[i24.u32[3]];
+	tbl[3] = *ptbl;
+
+	/* get 4 indexes for tbl8[]. */
+	i8.x = ip;
+	i8.u64[0] &= mask8.u64[0];
+	i8.u64[1] &= mask8.u64[1];
+
+	pt = (uint64_t)tbl[0] |
+		(uint64_t)tbl[1] << 32;
+	pt2 = (uint64_t)tbl[2] |
+		(uint64_t)tbl[3] << 32;
+
+	/* search successfully finished for all 4 IP addresses. */
+	if (likely((pt & mask_xv) == mask_v) &&
+			likely((pt2 & mask_xv) == mask_v)) {
+		*(uint64_t *)hop = pt & RTE_LPM_MASKX4_RES;
+		*(uint64_t *)(hop + 2) = pt2 & RTE_LPM_MASKX4_RES;
+		return;
+	}
+
+	if (unlikely((pt & RTE_LPM_VALID_EXT_ENTRY_BITMASK) ==
+			RTE_LPM_VALID_EXT_ENTRY_BITMASK)) {
+		i8.u32[0] = i8.u32[0] +
+			(tbl[0] & 0x00FFFFFF) * RTE_LPM_TBL8_GROUP_NUM_ENTRIES;
+		ptbl = (const uint32_t *)&lpm->tbl8[i8.u32[0]];
+		tbl[0] = *ptbl;
+	}
+	if (unlikely((pt >> 32 & RTE_LPM_VALID_EXT_ENTRY_BITMASK) ==
+			RTE_LPM_VALID_EXT_ENTRY_BITMASK)) {
+		i8.u32[1] = i8.u32[1] +
+			(tbl[1] & 0x00FFFFFF) * RTE_LPM_TBL8_GROUP_NUM_ENTRIES;
+		ptbl = (const uint32_t *)&lpm->tbl8[i8.u32[1]];
+		tbl[1] = *ptbl;
+	}
+	if (unlikely((pt2 & RTE_LPM_VALID_EXT_ENTRY_BITMASK) ==
+			RTE_LPM_VALID_EXT_ENTRY_BITMASK)) {
+		i8.u32[2] = i8.u32[2] +
+			(tbl[2] & 0x00FFFFFF) * RTE_LPM_TBL8_GROUP_NUM_ENTRIES;
+		ptbl = (const uint32_t *)&lpm->tbl8[i8.u32[2]];
+		tbl[2] = *ptbl;
+	}
+	if (unlikely((pt2 >> 32 & RTE_LPM_VALID_EXT_ENTRY_BITMASK) ==
+			RTE_LPM_VALID_EXT_ENTRY_BITMASK)) {
+		i8.u32[3] = i8.u32[3] +
+			(tbl[3] & 0x00FFFFFF) * RTE_LPM_TBL8_GROUP_NUM_ENTRIES;
+		ptbl = (const uint32_t *)&lpm->tbl8[i8.u32[3]];
+		tbl[3] = *ptbl;
+	}
+
+	hop[0] = (tbl[0] & RTE_LPM_LOOKUP_SUCCESS) ? tbl[0] & 0x00FFFFFF : defv;
+	hop[1] = (tbl[1] & RTE_LPM_LOOKUP_SUCCESS) ? tbl[1] & 0x00FFFFFF : defv;
+	hop[2] = (tbl[2] & RTE_LPM_LOOKUP_SUCCESS) ? tbl[2] & 0x00FFFFFF : defv;
+	hop[3] = (tbl[3] & RTE_LPM_LOOKUP_SUCCESS) ? tbl[3] & 0x00FFFFFF : defv;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_LPM_SCALAR_H_ */
-- 
2.30.2