From: Jakub Kicinski <kuba@kernel.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: Simon Horman <simon.horman@corigine.com>,
"David S. Miller" <davem@davemloft.net>,
Nick Desaulniers <ndesaulniers@google.com>,
oss-drivers@corigine.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
llvm@lists.linux.dev
Subject: Re: [PATCH] nfp: bpf: Fix bitwise vs. logical OR warning
Date: Mon, 18 Oct 2021 14:54:03 -0700 [thread overview]
Message-ID: <20211018145403.5eb2807d@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <20211018193101.2340261-1-nathan@kernel.org>
On Mon, 18 Oct 2021 12:31:01 -0700 Nathan Chancellor wrote:
> A new warning in clang points out two places in this driver where
> boolean expressions are being used with a bitwise OR instead of a
> logical one:
>
> drivers/net/ethernet/netronome/nfp/nfp_asm.c:199:20: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]
> reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ||
> drivers/net/ethernet/netronome/nfp/nfp_asm.c:199:20: note: cast one or both operands to int to silence this warning
> drivers/net/ethernet/netronome/nfp/nfp_asm.c:280:20: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]
> reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ||
> drivers/net/ethernet/netronome/nfp/nfp_asm.c:280:20: note: cast one or both operands to int to silence this warning
> 2 errors generated.
>
> The motivation for the warning is that logical operations short circuit
> while bitwise operations do not. In this case, it does not seem like
> short circuiting is harmful so implement the suggested fix of changing
> to a logical operation to fix the warning.
Warning seems generally useful, although in this case it is a little
out of place (swreg_lmextn() is a field extractor after all).
Applied to net, but without the Fixes tag, thanks!
prev parent reply other threads:[~2021-10-18 21:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-18 19:31 [PATCH] nfp: bpf: Fix bitwise vs. logical OR warning Nathan Chancellor
2021-10-18 19:39 ` Nick Desaulniers
2021-10-18 19:40 ` Nick Desaulniers
2021-10-18 21:54 ` Jakub Kicinski [this message]
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