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From: "adam at consulting dot net.nz" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/53623] [4.7/4.8 Regression] sign extension is effectively split into two x86-64 instructions Date: Sun, 10 Jun 2012 23:32:00 -0000 [thread overview] Message-ID: <bug-53623-4-MymTvzxz3V@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-53623-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53623 --- Comment #3 from Adam Warner <adam at consulting dot net.nz> 2012-06-10 23:32:19 UTC --- (Off topic "Note" correction) In my previous note I suggested the instruction "movsbq dh -> rdx". There is no such instruction! One cannot encode register ah/bh/ch/dh in an instruction requiring a REX prefix. A REX prefix would be required for sign extending ah/bh/ch/dh to 64 bits. My note does apply to zero extending dh to 64 bits. "movzbl dh -> edx" achieves this since edx is implicitly zero extended to rdx.
next prev parent reply other threads:[~2012-06-10 23:32 UTC|newest] Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-06-10 2:50 [Bug target/53623] New: [4.7 " adam at consulting dot net.nz 2012-06-10 14:39 ` [Bug middle-end/53623] " hjl.tools at gmail dot com 2012-06-10 14:43 ` [Bug middle-end/53623] [4.7/4.8 " hjl.tools at gmail dot com 2012-06-10 23:32 ` adam at consulting dot net.nz [this message] 2012-06-11 9:47 ` rguenth at gcc dot gnu.org 2012-06-11 12:21 ` jakub at gcc dot gnu.org 2012-09-20 10:28 ` jakub at gcc dot gnu.org 2012-12-03 15:32 ` rguenth at gcc dot gnu.org 2013-04-11 8:00 ` [Bug middle-end/53623] [4.7/4.8/4.9 " rguenth at gcc dot gnu.org 2013-12-13 5:24 ` law at redhat dot com 2014-01-08 6:03 ` law at redhat dot com 2014-01-08 6:03 ` law at gcc dot gnu.org 2015-02-15 14:06 ` hjl.tools at gmail dot com 2015-02-15 14:08 ` hjl.tools at gmail dot com 2015-02-15 16:03 ` [Bug middle-end/53623] [4.7/4.8 " hjl.tools at gmail dot com 2015-02-15 17:51 ` hjl.tools at gmail dot com 2015-02-16 9:00 ` [Bug middle-end/53623] [4.8 " rguenth at gcc dot gnu.org 2015-06-22 14:22 ` rguenth at gcc dot gnu.org 2015-06-23 8:46 ` rguenth at gcc dot gnu.org
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