{"action":"created","issue":{"url":"https://api.github.com/repos/golang/go/issues/14995","repository_url":"https://api.github.com/repos/golang/go","labels_url":"https://api.github.com/repos/golang/go/issues/14995/labels{/name}","comments_url":"https://api.github.com/repos/golang/go/issues/14995/comments","events_url":"https://api.github.com/repos/golang/go/issues/14995/events","html_url":"https://github.com/golang/go/issues/14995","id":144015603,"number":14995,"title":"cmd/compile: BLAS Idamax regression","user":{"login":"btracey","id":3680859,"avatar_url":"https://avatars.githubusercontent.com/u/3680859?v=3","gravatar_id":"","url":"https://api.github.com/users/btracey","html_url":"https://github.com/btracey","followers_url":"https://api.github.com/users/btracey/followers","following_url":"https://api.github.com/users/btracey/following{/other_user}","gists_url":"https://api.github.com/users/btracey/gists{/gist_id}","starred_url":"https://api.github.com/users/btracey/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/btracey/subscriptions","organizations_url":"https://api.github.com/users/btracey/orgs","repos_url":"https://api.github.com/users/btracey/repos","events_url":"https://api.github.com/users/btracey/events{/privacy}","received_events_url":"https://api.github.com/users/btracey/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":3,"created_at":"2016-03-28T16:12:46Z","updated_at":"2016-03-28T16:45:36Z","closed_at":null,"body":"The blas routine Idamax is seeing a regression between 1.6 and tip (go version go version devel +7e88826 Mon Mar 28 14:10:21 2016 +0000 darwin/amd64).\r\n\r\nIdamax finds the index with maximum absolute value. \r\n\r\n```\r\ngo get -u -t github.com/gonum/blas/native\r\ncd $GOPATH/src/github.com/gonum/blas/native\r\ngo test -bench=Ida -tags=noasm -count=5\r\n```\r\n\r\n```\r\nIdamaxSmallUnitaryInc-8   32.4ns ± 7%  39.1ns ± 6%  +20.80%  (p=0.008 n=5+5)\r\nIdamaxSmallPosInc-8       28.7ns ±11%  41.1ns ±11%  +43.24%  (p=0.008 n=5+5)\r\nIdamaxMediumUnitaryInc-8  1.58µs ± 2%  2.03µs ± 2%  +27.83%  (p=0.008 n=5+5)\r\nIdamaxMediumPosInc-8      1.86µs ± 2%  2.38µs ±11%  +27.93%  (p=0.008 n=5+5)\r\nIdamaxLargeUnitaryInc-8    150µs ± 2%   195µs ± 1%  +30.23%  (p=0.008 n=5+5)\r\nIdamaxLargePosInc-8        202µs ± 1%   241µs ± 2%  +19.10%  (p=0.008 n=5+5)\r\nIdamaxHugeUnitaryInc-8    15.1ms ± 1%  21.0ms ± 2%  +39.67%  (p=0.008 n=5+5)\r\nIdamaxHugePosInc-8        27.9ms ± 3%  30.0ms ± 2%   +7.38%  (p=0.008 n=5+5)\r\n```\r\n\r\n@randall77 @josharian "},"comment":{"url":"https://api.github.com/repos/golang/go/issues/comments/202480019","html_url":"https://github.com/golang/go/issues/14995#issuecomment-202480019","issue_url":"https://api.github.com/repos/golang/go/issues/14995","id":202480019,"user":{"login":"randall77","id":6889504,"avatar_url":"https://avatars.githubusercontent.com/u/6889504?v=3","gravatar_id":"","url":"https://api.github.com/users/randall77","html_url":"https://github.com/randall77","followers_url":"https://api.github.com/users/randall77/followers","following_url":"https://api.github.com/users/randall77/following{/other_user}","gists_url":"https://api.github.com/users/randall77/gists{/gist_id}","starred_url":"https://api.github.com/users/randall77/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/randall77/subscriptions","organizations_url":"https://api.github.com/users/randall77/orgs","repos_url":"https://api.github.com/users/randall77/repos","events_url":"https://api.github.com/users/randall77/events{/privacy}","received_events_url":"https://api.github.com/users/randall77/received_events","type":"User","site_admin":false},"created_at":"2016-03-28T16:45:36Z","updated_at":"2016-03-28T16:45:36Z","body":"It goes back to the layout pass.  We place the `idx` generating block after the phi, so the `i`-providing block is the primary predecessor.\r\n"}}