2021-10-18 19:34:12

by Nathan Chancellor

Subject: [PATCH] nfp: bpf: Fix bitwise vs. logical OR warning

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.

Link: https://github.com/ClangBuiltLinux/linux/issues/1479
Reported-by: Nick Desaulniers <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---
drivers/net/ethernet/netronome/nfp/nfp_asm.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_asm.c b/drivers/net/ethernet/netronome/nfp/nfp_asm.c
index 2643ea5948f4..154399c5453f 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_asm.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_asm.c
@@ -196,7 +196,7 @@ int swreg_to_unrestricted(swreg dst, swreg lreg, swreg rreg,
}

reg->dst_lmextn = swreg_lmextn(dst);
- reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
+ reg->src_lmextn = swreg_lmextn(lreg) || swreg_lmextn(rreg);

return 0;
}
@@ -277,7 +277,7 @@ int swreg_to_restricted(swreg dst, swreg lreg, swreg rreg,
}

reg->dst_lmextn = swreg_lmextn(dst);
- reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
+ reg->src_lmextn = swreg_lmextn(lreg) || swreg_lmextn(rreg);

return 0;
}

base-commit: 041c61488236a5a84789083e3d9f0a51139b6edf
--
2.33.1.637.gf443b226ca

2021-10-18 19:42:02

by Nick Desaulniers

Subject: Re: [PATCH] nfp: bpf: Fix bitwise vs. logical OR warning

On Mon, Oct 18, 2021 at 12:31 PM Nathan Chancellor <[email protected]> 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.

I agree. Thanks for the patch.
Reviewed-by: Nick Desaulniers <[email protected]>

>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1479
> Reported-by: Nick Desaulniers <[email protected]>
> Signed-off-by: Nathan Chancellor <[email protected]>
> ---
> drivers/net/ethernet/netronome/nfp/nfp_asm.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/netronome/nfp/nfp_asm.c b/drivers/net/ethernet/netronome/nfp/nfp_asm.c
> index 2643ea5948f4..154399c5453f 100644
> --- a/drivers/net/ethernet/netronome/nfp/nfp_asm.c
> +++ b/drivers/net/ethernet/netronome/nfp/nfp_asm.c
> @@ -196,7 +196,7 @@ int swreg_to_unrestricted(swreg dst, swreg lreg, swreg rreg,
> }
>
> reg->dst_lmextn = swreg_lmextn(dst);
> - reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
> + reg->src_lmextn = swreg_lmextn(lreg) || swreg_lmextn(rreg);
>
> return 0;
> }
> @@ -277,7 +277,7 @@ int swreg_to_restricted(swreg dst, swreg lreg, swreg rreg,
> }
>
> reg->dst_lmextn = swreg_lmextn(dst);
> - reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
> + reg->src_lmextn = swreg_lmextn(lreg) || swreg_lmextn(rreg);
>
> return 0;
> }
>
> base-commit: 041c61488236a5a84789083e3d9f0a51139b6edf
> --
> 2.33.1.637.gf443b226ca
>
>


--
Thanks,
~Nick Desaulniers

2021-10-18 19:42:12

by Nick Desaulniers

Subject: Re: [PATCH] nfp: bpf: Fix bitwise vs. logical OR warning

On Mon, Oct 18, 2021 at 12:39 PM Nick Desaulniers
<[email protected]> wrote:
>
> On Mon, Oct 18, 2021 at 12:31 PM Nathan Chancellor <[email protected]> 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.
>
> I agree. Thanks for the patch.
> Reviewed-by: Nick Desaulniers <[email protected]>

Perhaps:

Fixes: 995e101ffa71 ("nfp: bpf: encode extended LM pointer operands")

>
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1479
> > Reported-by: Nick Desaulniers <[email protected]>
> > Signed-off-by: Nathan Chancellor <[email protected]>
> > ---
> > drivers/net/ethernet/netronome/nfp/nfp_asm.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/netronome/nfp/nfp_asm.c b/drivers/net/ethernet/netronome/nfp/nfp_asm.c
> > index 2643ea5948f4..154399c5453f 100644
> > --- a/drivers/net/ethernet/netronome/nfp/nfp_asm.c
> > +++ b/drivers/net/ethernet/netronome/nfp/nfp_asm.c
> > @@ -196,7 +196,7 @@ int swreg_to_unrestricted(swreg dst, swreg lreg, swreg rreg,
> > }
> >
> > reg->dst_lmextn = swreg_lmextn(dst);
> > - reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
> > + reg->src_lmextn = swreg_lmextn(lreg) || swreg_lmextn(rreg);
> >
> > return 0;
> > }
> > @@ -277,7 +277,7 @@ int swreg_to_restricted(swreg dst, swreg lreg, swreg rreg,
> > }
> >
> > reg->dst_lmextn = swreg_lmextn(dst);
> > - reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
> > + reg->src_lmextn = swreg_lmextn(lreg) || swreg_lmextn(rreg);
> >
> > return 0;
> > }
> >
> > base-commit: 041c61488236a5a84789083e3d9f0a51139b6edf
> > --
> > 2.33.1.637.gf443b226ca
> >
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers



--
Thanks,
~Nick Desaulniers

2021-10-18 21:58:33

by Jakub Kicinski

Subject: Re: [PATCH] nfp: bpf: Fix bitwise vs. logical OR warning

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!