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From: "carlos at systemhalted dot org" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sources.redhat.com Subject: [Bug ports/13742] New: Use of fsincos is incorrect for large input on m68k Date: Fri, 24 Feb 2012 16:13:00 -0000 [thread overview] Message-ID: <bug-13742-131@http.sourceware.org/bugzilla/> (raw) http://sourceware.org/bugzilla/show_bug.cgi?id=13742 Bug #: 13742 Summary: Use of fsincos is incorrect for large input on m68k Product: glibc Version: unspecified Status: NEW Severity: normal Priority: P2 Component: ports AssignedTo: unassigned@sourceware.org ReportedBy: carlos@systemhalted.org CC: carlos@systemhalted.org, roland@gnu.org, schwab@linux-m68k.org Classification: Unclassified Target: m68k-linux-gnu This bug: http://sourceware.org/bugzilla/show_bug.cgi?id=13658 Raises the question of the accuracy of hardware fsincos instructions for large inputs. It would appear that this bug, present on x86 and x86_64, would also effect m68k since it uses a fsincos instruction with limited accuracy at high input values. A quick grep shows: sysdeps/m68k/m680x0/fpu/s_csin.c: __asm ("fsincos%.x %2,%1:%0" : "=f" (sin_rx), "=f" (cos_rx) sysdeps/m68k/m680x0/fpu/bits/mathinline.h: __asm ("fsincos%.x %2,%1:%0" \ sysdeps/m68k/m680x0/fpu/k_sin.c: __asm__ __volatile__ ("fsincosx %2,%0:%1" : "=f" (cos_x), "=f" (sin_x) sysdeps/m68k/m680x0/fpu/k_sin.c: __asm__ __volatile__ ("fsincosx %2,%0:%1" : "=f" (cos_y), "=f" (sin_y) sysdeps/m68k/m680x0/fpu/s_ccosh.c: __asm ("fsincos%.x %2,%1:%0" : "=f" (sin_ix), "=f" (cos_ix) sysdeps/m68k/m680x0/fpu/s_csinh.c: __asm ("fsincos%.x %2,%1:%0" : "=f" (sin_ix), "=f" (cos_ix) sysdeps/m68k/m680x0/fpu/k_cos.c: __asm__ __volatile__ ("fsincosx %2,%0:%1" : "=f" (cos_x), "=f" (sin_x) sysdeps/m68k/m680x0/fpu/k_cos.c: __asm__ __volatile__ ("fsincosx %2,%0:%1" : "=f" (cos_y), "=f" (sin_y) sysdeps/m68k/m680x0/fpu/s_cexp.c: __asm ("fsincos%.x %2,%1:%0" : "=f" (sin_ix), "=f" (cos_ix) A quick inspection does not show any input argument reduction. The M68000PM/AD REV.1 states loss of accuracy if the input is > 10^20. Therefore it seems to me that the m68k port also suffers the same problems as x86 and x86_64. -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.
next reply other threads:[~2012-02-24 16:13 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-02-24 16:13 carlos at systemhalted dot org [this message] 2012-02-24 16:13 ` [Bug ports/13742] " carlos at systemhalted dot org 2012-04-05 9:28 ` aj at suse dot de 2014-02-11 0:31 ` [Bug math/13742] [m68k] " jsm28 at gcc dot gnu.org 2014-06-26 15:15 ` fweimer at redhat dot com
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