Re: [dpdk-dev] [PATCH] acl: fix build issue with some arm64 compiler

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

On 6/6/19 10:50 AM, mailto:jerinj@marvell.com wrote:
From: Jerin Jacob mailto:jerinj@marvell.com

Some compilers reporting the following error, though the existing
code doesn't have any uninitialized variable case.
Just to make compiler happy, initialize the int32x4_t variable
one shot in C language.

../lib/librte_acl/acl_run_neon.h: In function 'search_neon_4'
../lib/librte_acl/acl_run_neon.h:230:12: error: 'input' may be
used uninitialized in this function [-Werror=maybe-uninitialized]
  int32x4_t input;

Fixes: 34fa6c27c156 ("acl: add NEON optimization for ARMv8")
Cc: mailto:stable@dpdk.org

Signed-off-by: Jerin Jacob mailto:jerinj@marvell.com
---
 lib/librte_acl/acl_run_neon.h | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/lib/librte_acl/acl_run_neon.h b/lib/librte_acl/acl_run_neon.h
index 01b9766d8..dc9e9efe9 100644
--- a/lib/librte_acl/acl_run_neon.h
+++ b/lib/librte_acl/acl_run_neon.h
@@ -165,7 +165,6 @@ search_neon_8(const struct rte_acl_ctx *ctx, const uint8_t **data,
 	uint64_t index_array[8];
 	struct completion cmplt[8];
 	struct parms parms[8];
-	int32x4_t input0, input1;
 
 	acl_set_flow(&flows, cmplt, RTE_DIM(cmplt), data, results,
 		     total_packets, categories, ctx->trans_table);
@@ -181,17 +180,14 @@ search_neon_8(const struct rte_acl_ctx *ctx, const uint8_t **data,
 
 	while (flows.started > 0) {
 		/* Gather 4 bytes of input data for each stream. */
-		input0 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 0), input0, 0);
-		input1 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 4), input1, 0);
-
-		input0 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 1), input0, 1);
-		input1 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 5), input1, 1);
-
-		input0 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 2), input0, 2);
-		input1 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 6), input1, 2);
-
-		input0 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 3), input0, 3);
-		input1 = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 7), input1, 3);
+		int32x4_t input0 = {GET_NEXT_4BYTES(parms, 0),
+				    GET_NEXT_4BYTES(parms, 1),
+				    GET_NEXT_4BYTES(parms, 2),
+				    GET_NEXT_4BYTES(parms, 3)};
+		int32x4_t input1 = {GET_NEXT_4BYTES(parms, 4),
+				    GET_NEXT_4BYTES(parms, 5),
+				    GET_NEXT_4BYTES(parms, 6),
+				    GET_NEXT_4BYTES(parms, 7)};
 
 		/* Process the 4 bytes of input on each stream. */
 
@@ -227,7 +223,6 @@ search_neon_4(const struct rte_acl_ctx *ctx, const uint8_t **data,
 	uint64_t index_array[4];
 	struct completion cmplt[4];
 	struct parms parms[4];
-	int32x4_t input;
 
 	acl_set_flow(&flows, cmplt, RTE_DIM(cmplt), data, results,
 		     total_packets, categories, ctx->trans_table);
@@ -242,10 +237,10 @@ search_neon_4(const struct rte_acl_ctx *ctx, const uint8_t **data,
 
 	while (flows.started > 0) {
 		/* Gather 4 bytes of input data for each stream. */
-		input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 0), input, 0);
-		input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 1), input, 1);
-		input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 2), input, 2);
-		input = vsetq_lane_s32(GET_NEXT_4BYTES(parms, 3), input, 3);
+		int32x4_t input = {GET_NEXT_4BYTES(parms, 0),
+				   GET_NEXT_4BYTES(parms, 1),
+				   GET_NEXT_4BYTES(parms, 2),
+				   GET_NEXT_4BYTES(parms, 3)};
 
 		/* Process the 4 bytes of input on each stream. */
 		input = transition4(input, flows.trans, index_array);
Fixed on travis: https://travis-ci.com/Maickii/dpdk-2/builds/114612090
Acked-by: Michael Santana mailto:msantana@redhat.com

[Honnappa] Prefer to go with Aaron's patch with a temp variable for setting the first lane. Mixing of NEON intrinsics and GCC vector extensions is not recommended as per Arm C Language Extensions guide 12.2.6