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examples/l3fwd: fix aliasing in port grouping

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With -f-strict-aliasing enabled by default from -O2, gcc > 5.x gives
undefined behavior in port_groupx4 in ARM. 'pn' and 'pnum' are
two different pointers pointing to same chunk of memory and
with -f-strict-aliasing the pointers are assumed to be pointing to
different memory and compiler reorders instructions that depend on
pnum and pn. This breaks port grouping algorithm.

This patch eliminates the above problem by introducing a compiler
barrier between the instructions that depend on pnum, pn and lp.

Fixes: 569b290cdb36 ("examples/l3fwd: add NEON implementation")
Cc: stable@dpdk.org

Signed-off-by: Guduri Prathyusha <gprathyusha@caviumnetworks.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Acked-by: Jianbo Liu <jianbo.liu@arm.com>
This commit is contained in:
Guduri Prathyusha 2017-11-03 16:13:51 +05:30 committed by Ferruh Yigit
parent 3a4475e51d
commit 01ac23460c
1 changed files with 1 additions and 0 deletions
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examples/l3fwd/l3fwd_neon.h
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@ -114,6 +114,7 @@ port_groupx4(uint16_t pn[FWDSTEP + 1], uint16_t *lp, uint16x8_t dp1,
/* update last port counter. */
lp[0] += gptbl[v].lpv;
rte_compiler_barrier();
/* if dest port value has changed. */
if (v != GRPMSK) {