{"action":"created","issue":{"url":"https://api.github.com/repos/eschkufz/x64asm/issues/158","labels_url":"https://api.github.com/repos/eschkufz/x64asm/issues/158/labels{/name}","comments_url":"https://api.github.com/repos/eschkufz/x64asm/issues/158/comments","events_url":"https://api.github.com/repos/eschkufz/x64asm/issues/158/events","html_url":"https://github.com/eschkufz/x64asm/issues/158","id":58533367,"number":158,"title":"and $0xff, %edi assembles wrong","user":{"login":"bchurchill","id":640745,"avatar_url":"https://avatars.githubusercontent.com/u/640745?v=3","gravatar_id":"","url":"https://api.github.com/users/bchurchill","html_url":"https://github.com/bchurchill","followers_url":"https://api.github.com/users/bchurchill/followers","following_url":"https://api.github.com/users/bchurchill/following{/other_user}","gists_url":"https://api.github.com/users/bchurchill/gists{/gist_id}","starred_url":"https://api.github.com/users/bchurchill/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/bchurchill/subscriptions","organizations_url":"https://api.github.com/users/bchurchill/orgs","repos_url":"https://api.github.com/users/bchurchill/repos","events_url":"https://api.github.com/users/bchurchill/events{/privacy}","received_events_url":"https://api.github.com/users/bchurchill/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/eschkufz/x64asm/labels/bug","name":"bug","color":"fc2929"},{"url":"https://api.github.com/repos/eschkufz/x64asm/labels/Medium!","name":"Medium!","color":"fbca04"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":5,"created_at":"2015-02-23T01:31:13Z","updated_at":"2015-02-23T23:20:11Z","closed_at":null,"body":"```\r\n$ ./asm\r\nandl $0xff, %edi\r\n83 e7 ff\r\n```\r\n\r\nbut if you objdump this:\r\n```\r\n0000000000000000 <.data>:\r\n   0:\t83 e7 ff             \tand    $0xffffffff,%edi\r\n   3:\tc3                   \tretq\r\n```"},"comment":{"url":"https://api.github.com/repos/eschkufz/x64asm/issues/comments/75659920","html_url":"https://github.com/eschkufz/x64asm/issues/158#issuecomment-75659920","issue_url":"https://api.github.com/repos/eschkufz/x64asm/issues/158","id":75659920,"user":{"login":"bchurchill","id":640745,"avatar_url":"https://avatars.githubusercontent.com/u/640745?v=3","gravatar_id":"","url":"https://api.github.com/users/bchurchill","html_url":"https://github.com/bchurchill","followers_url":"https://api.github.com/users/bchurchill/followers","following_url":"https://api.github.com/users/bchurchill/following{/other_user}","gists_url":"https://api.github.com/users/bchurchill/gists{/gist_id}","starred_url":"https://api.github.com/users/bchurchill/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/bchurchill/subscriptions","organizations_url":"https://api.github.com/users/bchurchill/orgs","repos_url":"https://api.github.com/users/bchurchill/repos","events_url":"https://api.github.com/users/bchurchill/events{/privacy}","received_events_url":"https://api.github.com/users/bchurchill/received_events","type":"User","site_admin":false},"created_at":"2015-02-23T23:20:11Z","updated_at":"2015-02-23T23:20:11Z","body":"To be clear, the difference is that if you AND with 0xff, this zeros all but the lower byte; if you AND with 0xffffffff, this is a no-op on a 32-bit register.  If you use the short one-byte form, it will always do the latter; if you do the long from, it can do both."}}