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From: "nathanael.schaeffer at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/60237] isnan fails with -ffast-math Date: Mon, 17 Feb 2014 11:38:00 -0000 [thread overview] Message-ID: <bug-60237-4-UyzdSujDpq@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-60237-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60237 --- Comment #4 from N Schaeffer <nathanael.schaeffer at gmail dot com> --- int my_isnan(double x){ volatile double y=x; return y!=y; } is translated to: 0x0000000000406cf0 <+0>: movsd QWORD PTR [rsp-0x8],xmm0 0x0000000000406cf6 <+6>: xor eax,eax 0x0000000000406cf8 <+8>: movsd xmm1,QWORD PTR [rsp-0x8] 0x0000000000406cfe <+14>: movsd xmm0,QWORD PTR [rsp-0x8] 0x0000000000406d04 <+20>: comisd xmm1,xmm0 0x0000000000406d08 <+24>: setne al 0x0000000000406d0b <+27>: ret which also fails to detect NaN, which is right according to the documented behaviour of comisd: http://www.jaist.ac.jp/iscenter-new/mpc/altix/altixdata/opt/intel/vtune/doc/users_guide/mergedProjects/analyzer_ec/mergedProjects/reference_olh/mergedProjects/instructions/instruct32_hh/vc44.htm
next prev parent reply other threads:[~2014-02-17 11:38 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-02-17 10:41 [Bug c++/60237] New: " nathanael.schaeffer at gmail dot com 2014-02-17 10:53 ` [Bug c++/60237] " jakub at gcc dot gnu.org 2014-02-17 11:16 ` nathanael.schaeffer at gmail dot com 2014-02-17 11:26 ` glisse at gcc dot gnu.org 2014-02-17 11:38 ` nathanael.schaeffer at gmail dot com [this message] 2014-02-17 12:46 ` rguenth at gcc dot gnu.org 2014-02-17 16:16 ` nathanael.schaeffer at gmail dot com 2014-02-17 17:28 ` glisse at gcc dot gnu.org
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