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From: "yuri at tsoft dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/41462] New: redundant instructions with long double returned value Date: Thu, 24 Sep 2009 17:24:00 -0000 [thread overview] Message-ID: <bug-41462-6649@http.gcc.gnu.org/bugzilla/> (raw) When I compile this function: double f(long double i) {return (i);} with gcc flags -S -O3, I get the assembly below. There are two redundant FPU instructions there. double value is already in FPU after fldt. No need to store it and load it back since difference between double and long double is only in memory representation, and in FPU registers they are the same. ---- asm output (relevant part) ---- f: pushl %ebp movl %esp, %ebp subl $8, %esp <---- redundant related stack adjustment fldt 8(%ebp) fstpl -8(%ebp) <---- redundant STORE fldl -8(%ebp) <---- redundant LOAD leave ret -- Summary: redundant instructions with long double returned value Product: gcc Version: 4.4.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: yuri at tsoft dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41462
next reply other threads:[~2009-09-24 17:24 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2009-09-24 17:24 yuri at tsoft dot com [this message] 2009-09-24 17:25 ` [Bug c/41462] " yuri at tsoft dot com 2009-09-25 8:05 ` [Bug target/41462] " ubizjak at gmail dot com
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