patch 'hash: align SSE lookup to scalar implementation' has been queued to stable release 22.11.4

[Xueming Li]

Hi,

FYI, your patch has been queued to stable release 22.11.4

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 11/15/23. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://git.dpdk.org/dpdk-stable/log/?h=22.11-staging

This queued commit can be viewed at:
https://git.dpdk.org/dpdk-stable/commit/?h=22.11-staging&id=af391d2427d78f3c4dbf2b3e581e0b5edf6ca1c8

Thanks.

Xueming Li <xuemingl at nvidia.com>

---
>From af391d2427d78f3c4dbf2b3e581e0b5edf6ca1c8 Mon Sep 17 00:00:00 2001
From: Jieqiang Wang <jieqiang.wang at arm.com>
Date: Sat, 7 Oct 2023 15:36:34 +0800
Subject: [PATCH] hash: align SSE lookup to scalar implementation
Cc: Xueming Li <xuemingl at nvidia.com>

[ upstream commit e93bbaa72cca7ec912d756afdf10e393f9d71791 ]

__mm_cmpeq_epi16 returns 0xFFFF if the corresponding 16-bit elements are
equal. In original SSE2 implementation for function compare_signatures,
it utilizes _mm_movemask_epi8 to create mask from the MSB of each 8-bit
element, while we should only care about the MSB of lower 8-bit in each
16-bit element.

For example, if the comparison result is all equal, SSE2 path returns
0xFFFF while NEON and default scalar path return 0x5555.
Although this bug is not causing any negative effects since the caller
function solely examines the trailing zeros of each match mask, we
recommend this fix to ensure consistency with NEON and default scalar
code behaviors.

Fixes: c7d93df552c2 ("hash: use partial-key hashing")

Signed-off-by: Feifei Wang <feifei.wang2 at arm.com>
Signed-off-by: Jieqiang Wang <jieqiang.wang at arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
Acked-by: Bruce Richardson <bruce.richardson at intel.com>
---
 lib/hash/rte_cuckoo_hash.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/hash/rte_cuckoo_hash.c b/lib/hash/rte_cuckoo_hash.c
index 829b79c89a..a08b5dd875 100644
--- a/lib/hash/rte_cuckoo_hash.c
+++ b/lib/hash/rte_cuckoo_hash.c
@@ -1860,11 +1860,15 @@ compare_signatures(uint32_t *prim_hash_matches, uint32_t *sec_hash_matches,
 				_mm_load_si128(
 					(__m128i const *)prim_bkt->sig_current),
 				_mm_set1_epi16(sig)));
+		/* Extract the even-index bits only */
+		*prim_hash_matches &= 0x5555;
 		/* Compare all signatures in the bucket */
 		*sec_hash_matches = _mm_movemask_epi8(_mm_cmpeq_epi16(
 				_mm_load_si128(
 					(__m128i const *)sec_bkt->sig_current),
 				_mm_set1_epi16(sig)));
+		/* Extract the even-index bits only */
+		*sec_hash_matches &= 0x5555;
 		break;
 #elif defined(__ARM_NEON)
 	case RTE_HASH_COMPARE_NEON: {
--
2.25.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2023-10-22 22:17:35.298506800 +0800
+++ 0023-hash-align-SSE-lookup-to-scalar-implementation.patch	2023-10-22 22:17:34.156723700 +0800
@@ -1 +1 @@
-From e93bbaa72cca7ec912d756afdf10e393f9d71791 Mon Sep 17 00:00:00 2001
+From af391d2427d78f3c4dbf2b3e581e0b5edf6ca1c8 Mon Sep 17 00:00:00 2001
@@ -4,0 +5,3 @@
+Cc: Xueming Li <xuemingl at nvidia.com>
+
+[ upstream commit e93bbaa72cca7ec912d756afdf10e393f9d71791 ]
@@ -20 +22,0 @@
-Cc: stable at dpdk.org
@@ -31 +33 @@
-index d92a903bb3..19b23f2a97 100644
+index 829b79c89a..a08b5dd875 100644
@@ -34 +36 @@
-@@ -1868,11 +1868,15 @@ compare_signatures(uint32_t *prim_hash_matches, uint32_t *sec_hash_matches,
+@@ -1860,11 +1860,15 @@ compare_signatures(uint32_t *prim_hash_matches, uint32_t *sec_hash_matches,