From: "Wiles, Keith" <keith.wiles@intel.com>
To: Aleksey Baulin <aleksey.baulin@gmail.com>
Cc: Thomas Monjalon <thomas@monjalon.net>, "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] eal/common: better likely() and unlikely()
Date: Mon, 20 Nov 2017 13:36:28 +0000 [thread overview]
Message-ID: <D3302FD6-A529-497E-A470-5EBC1729EDF5@intel.com> (raw)
In-Reply-To: <1511129764-23123-1-git-send-email-Aleksey.Baulin@gmail.com>
> On Nov 19, 2017, at 4:16 PM, Aleksey Baulin <aleksey.baulin@gmail.com> wrote:
>
> A warning is issued when using an argument to likely() or unlikely()
> builtins which is evaluated to a pointer value, as __builtin_expect()
> expects a 'long int' type for its first argument. With this fix
> a pointer value is converted to an integer with the value of 0 or 1.
>
> Signed-off-by: Aleksey Baulin <Aleksey.Baulin@gmail.com>
> ---
> lib/librte_eal/common/include/rte_branch_prediction.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_eal/common/include/rte_branch_prediction.h b/lib/librte_eal/common/include/rte_branch_prediction.h
> index a6a56d1..2e7dc69 100644
> --- a/lib/librte_eal/common/include/rte_branch_prediction.h
> +++ b/lib/librte_eal/common/include/rte_branch_prediction.h
> @@ -50,7 +50,7 @@
> *
> */
> #ifndef likely
> -#define likely(x) __builtin_expect((x),1)
> +#define likely(x) __builtin_expect(!!(x), 1)
> #endif /* likely */
>
> /**
> @@ -64,7 +64,7 @@
> *
> */
> #ifndef unlikely
> -#define unlikely(x) __builtin_expect((x),0)
> +#define unlikely(x) __builtin_expect(!!(x), 0)
I have not looked at the generated code, but does this add some extra instruction now to do the !!(x) ?
> #endif /* unlikely */
>
> #endif /* _RTE_BRANCH_PREDICTION_H_ */
> --
> 2.7.4
>
Regards,
Keith
next prev parent reply other threads:[~2017-11-20 13:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-19 22:16 Aleksey Baulin
2017-11-20 13:36 ` Wiles, Keith [this message]
2017-11-20 17:21 ` Jim Thompson
2017-11-21 7:05 ` Aleksey Baulin
2018-01-12 15:35 ` Thomas Monjalon
2018-01-13 22:05 ` Aleksey Baulin
2018-01-13 22:24 ` Thomas Monjalon
2018-01-13 22:45 ` Aleksey Baulin
2018-01-14 17:17 ` Stephen Hemminger
2018-01-20 16:28 ` Thomas Monjalon
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