{"action":"created","issue":{"url":"https://api.github.com/repos/libjpeg-turbo/libjpeg-turbo/issues/290","repository_url":"https://api.github.com/repos/libjpeg-turbo/libjpeg-turbo","labels_url":"https://api.github.com/repos/libjpeg-turbo/libjpeg-turbo/issues/290/labels{/name}","comments_url":"https://api.github.com/repos/libjpeg-turbo/libjpeg-turbo/issues/290/comments","events_url":"https://api.github.com/repos/libjpeg-turbo/libjpeg-turbo/issues/290/events","html_url":"https://github.com/libjpeg-turbo/libjpeg-turbo/pull/290","id":365172313,"node_id":"MDExOlB1bGxSZXF1ZXN0MjE5MTcyODQx","number":290,"title":"simd, cmake: add ability to NOT build 3DNow support","user":{"login":"branch-predictor","id":12440680,"node_id":"MDQ6VXNlcjEyNDQwNjgw","avatar_url":"https://avatars3.githubusercontent.com/u/12440680?v=4","gravatar_id":"","url":"https://api.github.com/users/branch-predictor","html_url":"https://github.com/branch-predictor","followers_url":"https://api.github.com/users/branch-predictor/followers","following_url":"https://api.github.com/users/branch-predictor/following{/other_user}","gists_url":"https://api.github.com/users/branch-predictor/gists{/gist_id}","starred_url":"https://api.github.com/users/branch-predictor/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/branch-predictor/subscriptions","organizations_url":"https://api.github.com/users/branch-predictor/orgs","repos_url":"https://api.github.com/users/branch-predictor/repos","events_url":"https://api.github.com/users/branch-predictor/events{/privacy}","received_events_url":"https://api.github.com/users/branch-predictor/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":2,"created_at":"2018-09-29T22:32:04Z","updated_at":"2018-09-30T16:54:58Z","closed_at":null,"author_association":"NONE","pull_request":{"url":"https://api.github.com/repos/libjpeg-turbo/libjpeg-turbo/pulls/290","html_url":"https://github.com/libjpeg-turbo/libjpeg-turbo/pull/290","diff_url":"https://github.com/libjpeg-turbo/libjpeg-turbo/pull/290.diff","patch_url":"https://github.com/libjpeg-turbo/libjpeg-turbo/pull/290.patch"},"body":"AMD has dropped support for 3DNow instructions over 8 years ago, so in most\r\ncases AMD processors will utilize SSE, SSE2 and/or AVX code path, leaving\r\n3DNow code untouched and just taking storage space.\r\nThis commit adds new cmake option (WITH_3DNOW) that defaults to TRUE and\r\ncan be changed to FALSE to entirely disable 3DNow support.\r\n\r\nSigned-off-by: Piotr Dałek <git@predictor.org.pl>"},"comment":{"url":"https://api.github.com/repos/libjpeg-turbo/libjpeg-turbo/issues/comments/425734757","html_url":"https://github.com/libjpeg-turbo/libjpeg-turbo/pull/290#issuecomment-425734757","issue_url":"https://api.github.com/repos/libjpeg-turbo/libjpeg-turbo/issues/290","id":425734757,"node_id":"MDEyOklzc3VlQ29tbWVudDQyNTczNDc1Nw==","user":{"login":"dcommander","id":651941,"node_id":"MDQ6VXNlcjY1MTk0MQ==","avatar_url":"https://avatars0.githubusercontent.com/u/651941?v=4","gravatar_id":"","url":"https://api.github.com/users/dcommander","html_url":"https://github.com/dcommander","followers_url":"https://api.github.com/users/dcommander/followers","following_url":"https://api.github.com/users/dcommander/following{/other_user}","gists_url":"https://api.github.com/users/dcommander/gists{/gist_id}","starred_url":"https://api.github.com/users/dcommander/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/dcommander/subscriptions","organizations_url":"https://api.github.com/users/dcommander/orgs","repos_url":"https://api.github.com/users/dcommander/repos","events_url":"https://api.github.com/users/dcommander/events{/privacy}","received_events_url":"https://api.github.com/users/dcommander/received_events","type":"User","site_admin":false},"created_at":"2018-09-30T16:54:58Z","updated_at":"2018-09-30T16:54:58Z","author_association":"MEMBER","body":"OK, but my point is:  the vast majority of your bandwidth savings comes from eliminating the encoder, and those changes cannot be checked in upstream.  Eliminating the 3DNow! extensions only saved you a few kilobytes.  In other words, there is ultimately no way to get what you want by using a pristine libjpeg-turbo source base, so I don't see the point of checking in this trivial patch.  If you are already having to maintain a custom build without the encoder, then you can maintain a custom build without the 3DNow! extensions as well.  Your comment above indicates that your reasoning behind eliminating those extensions is largely based on your personal assessment of how many users would be affected.  From my point of view, if the 3DNow! extensions can be shown to be of some benefit on some processors, then they need to stay in.  If they can't be shown to be of any benefit, then they need to be removed (although I would not remove them until libjpeg-turbo 2.1.)  But making them compile-time optional seems like sending a nuke to kill an ant.  Every on/off switch that is introduced into the libjpeg-turbo code base doubles the number of possible configurations, which doubles the number of configurations that need to be tested.  Thus, I would very much like to avoid introducing any new switches unless they are of some potential benefit to a large number of libjpeg-turbo users.\r\n"}}
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