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[81.97.203.96]) by smtp.gmail.com with ESMTPSA id u17-20020a05600c19d100b003e204fdb160sm2908206wmq.3.2023.03.15.11.01.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Mar 2023 11:01:47 -0700 (PDT) Date: Wed, 15 Mar 2023 18:01:45 +0000 From: "Dr. David Alan Gilbert" To: Matheus Tavares Bernardino Cc: qemu-devel@nongnu.org, quintela@redhat.com, bcain@quicinc.com, ling1.xu@intel.com, zhou.zhao@intel.com, jun.i.jin@intel.com Subject: Re: [PATCH RESEND v2 1/2] migration/xbzrle: use ctz64 to avoid undefined result Message-ID: References: <117f3c2fdc17c319b0e04014bbd7e0c94992c197.1678733663.git.quic_mathbern@quicinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <117f3c2fdc17c319b0e04014bbd7e0c94992c197.1678733663.git.quic_mathbern@quicinc.com> User-Agent: Mutt/2.2.9 (2022-11-12) Received-SPF: pass client-ip=170.10.129.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org * Matheus Tavares Bernardino (quic_mathbern@quicinc.com) wrote: > __builtin_ctzll() produces undefined results when the argument is 0. > This can be seen through test-xbzrle, which produces the following > warning: > > ../migration/xbzrle.c:265: runtime error: passing zero to ctz(), which is not a valid argument > > Replace __builtin_ctzll() with our ctz64() wrapper which properly > handles 0. > > Signed-off-by: Matheus Tavares Bernardino Reviewed-by: Dr. David Alan Gilbert > --- > migration/xbzrle.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/migration/xbzrle.c b/migration/xbzrle.c > index 05366e86c0..21b92d4eae 100644 > --- a/migration/xbzrle.c > +++ b/migration/xbzrle.c > @@ -12,6 +12,7 @@ > */ > #include "qemu/osdep.h" > #include "qemu/cutils.h" > +#include "qemu/host-utils.h" > #include "xbzrle.h" > > /* > @@ -233,7 +234,7 @@ int xbzrle_encode_buffer_avx512(uint8_t *old_buf, uint8_t *new_buf, int slen, > break; > } > never_same = false; > - num = __builtin_ctzll(~comp); > + num = ctz64(~comp); > num = (num < bytes_to_check) ? num : bytes_to_check; > zrun_len += num; > bytes_to_check -= num; > @@ -262,7 +263,7 @@ int xbzrle_encode_buffer_avx512(uint8_t *old_buf, uint8_t *new_buf, int slen, > nzrun_len += 64; > break; > } > - num = __builtin_ctzll(comp); > + num = ctz64(comp); > num = (num < bytes_to_check) ? num : bytes_to_check; > nzrun_len += num; > bytes_to_check -= num; > -- > 2.39.1 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK