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Thread-Topic: [PATCH] libstdc++: More efficient std::chrono::year::leap. 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charset="us-ascii" Content-ID: <775CDAB3EFF37646A70B3F063C744F42@namprd19.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: Dell.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SA0PR19MB4508.namprd19.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0bdcf241-01ad-4724-881f-08d91c82fbd6 X-MS-Exchange-CrossTenant-originalarrivaltime: 21 May 2021 18:05:14.5475 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 945c199a-83a2-4e80-9f8c-5a91be5752dd X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: RmX7ye1J3ELvHfd9U4+9EY+4X2oMy0oVYCvPfCqX9nzrkwoYsi6TjKU97TIgMU7YFpYxqschHem9gHBnhFF6NQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA0PR19MB4207 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.761 definitions=2021-05-21_08:2021-05-20, 2021-05-21 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 adultscore=0 priorityscore=1501 mlxscore=0 bulkscore=0 clxscore=1011 suspectscore=0 impostorscore=0 mlxlogscore=966 spamscore=0 malwarescore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2105210094 X-Proofpoint-ORIG-GUID: qxBHf5uaxAKy2XFBdaOYIFssUWx4D_A2 X-Proofpoint-GUID: qxBHf5uaxAKy2XFBdaOYIFssUWx4D_A2 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 phishscore=0 malwarescore=0 mlxlogscore=999 adultscore=0 bulkscore=0 suspectscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2105210094 X-Spam-Status: No, score=-3.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 21 May 2021 18:05:21 -0000 > On May 21, 2021, at 1:46 PM, Cassio Neri via Gcc-patches wrote: >=20 > Simple change to std::chrono::year::is_leap. If a year is multiple of 100= , > then it's divisible by 400 if and only if it's divisible by 16. The latte= r > allows for better code generation. I wonder if the optimizer could be taught to do that. The change seems correct but it is very confusing; at the very least the re= asoning you gave should be stated in a comment on that check. paul