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Thu, 28 May 2020 08:57:53 +0000 (UTC) Subject: Re: [PATCH v2] fpu/softfloat: Silent 'bitwise negation of a boolean expression' warning To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , qemu-devel@nongnu.org References: <20200528084833.9531-1-philmd@redhat.com> From: Thomas Huth Openpgp: preference=signencrypt Message-ID: <288fd554-67e2-bfd9-4b51-ac03e565161f@redhat.com> Date: Thu, 28 May 2020 10:57:51 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200528084833.9531-1-philmd@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=thuth@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/28 01:51:20 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Richard Henderson , =?UTF-8?Q?Alex_Benn=c3=a9e?= , Aurelien Jarno , Peter Maydell Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 28/05/2020 10.48, Philippe Mathieu-Daudé wrote: > When building with clang version 10.0.0-4ubuntu1, we get: > > CC lm32-softmmu/fpu/softfloat.o > fpu/softfloat.c:3365:13: error: bitwise negation of a boolean expression; did you mean logical negation? [-Werror,-Wbool-operation] > absZ &= ~ ( ( ( roundBits ^ 0x40 ) == 0 ) & roundNearestEven ); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > fpu/softfloat.c:3423:18: error: bitwise negation of a boolean expression; did you mean logical negation? [-Werror,-Wbool-operation] > absZ0 &= ~ ( ( (uint64_t) ( absZ1<<1 ) == 0 ) & roundNearestEven ); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > fpu/softfloat.c:3483:18: error: bitwise negation of a boolean expression; did you mean logical negation? [-Werror,-Wbool-operation] > absZ0 &= ~(((uint64_t)(absZ1<<1) == 0) & roundNearestEven); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > fpu/softfloat.c:3606:13: error: bitwise negation of a boolean expression; did you mean logical negation? [-Werror,-Wbool-operation] > zSig &= ~ ( ( ( roundBits ^ 0x40 ) == 0 ) & roundNearestEven ); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > fpu/softfloat.c:3760:13: error: bitwise negation of a boolean expression; did you mean logical negation? [-Werror,-Wbool-operation] > zSig &= ~ ( ( ( roundBits ^ 0x200 ) == 0 ) & roundNearestEven ); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > fpu/softfloat.c:3987:21: error: bitwise negation of a boolean expression; did you mean logical negation? [-Werror,-Wbool-operation] > ~ ( ( (uint64_t) ( zSig1<<1 ) == 0 ) & roundNearestEven ); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > fpu/softfloat.c:4003:22: error: bitwise negation of a boolean expression; did you mean logical negation? [-Werror,-Wbool-operation] > zSig0 &= ~ ( ( (uint64_t) ( zSig1<<1 ) == 0 ) & roundNearestEven ); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > fpu/softfloat.c:4273:18: error: bitwise negation of a boolean expression; did you mean logical negation? [-Werror,-Wbool-operation] > zSig1 &= ~ ( ( zSig2 + zSig2 == 0 ) & roundNearestEven ); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Fix by rewriting the fishy bitwise AND of two bools as an int. > > Suggested-by: Eric Blake > Buglink: https://bugs.launchpad.net/bugs/1881004 > Signed-off-by: Philippe Mathieu-Daudé > --- > v2: Resend without the Cc: "Toni Wilen " tag > --- > fpu/softfloat.c | 33 ++++++++++++++++++++++++--------- > 1 file changed, 24 insertions(+), 9 deletions(-) > > diff --git a/fpu/softfloat.c b/fpu/softfloat.c > index 6c8f2d597a..0dd57eddd7 100644 > --- a/fpu/softfloat.c > +++ b/fpu/softfloat.c > @@ -3362,7 +3362,9 @@ static int32_t roundAndPackInt32(bool zSign, uint64_t absZ, > } > roundBits = absZ & 0x7F; > absZ = ( absZ + roundIncrement )>>7; > - absZ &= ~ ( ( ( roundBits ^ 0x40 ) == 0 ) & roundNearestEven ); > + if (((roundBits ^ 0x40) == 0) && roundNearestEven) { > + absZ &= ~1; > + } You could get rid of some more parentheses now: if ((roundBits ^ 0x40) == 0 && roundNearestEven) ... also in the other hunks. Anyway: Reviewed-by: Thomas Huth