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Re: Enable
- To: "David H. Munro" <munro at icf dot llnl dot gov>
- Subject: Re: Enable
- From: Andreas Jaeger <aj at suse dot de>
- Date: 27 Oct 1999 12:53:31 +0200
- Cc: libc-alpha at sourceware dot cygnus dot com
- References: <199910041907.MAA16355@icf.llnl.gov.llnl.gov>
>>>>> David H Munro writes:
>> I'd much rather just [add] extra calls, `feenableexcept',
>> `fedisableexcept' which do this:
>>
>> int feenableexcept(int excepts);
>>
>> Returns a bitmap containing those exceptions in 'excepts' which were
>> enabled. Will not enable _more_ exceptions that 'excepts' specifies;
>> returns 0 if 'excepts' is not FE_ALL_EXCEPT and cannot enable or
>> disable exceptions individually.
>>
>> Note that on PPC, at least, you can test whether exceptions have
>> occurred at a finer level than you can enable or disable them. So if
>> you ask to have just FE_INVALID_SQRT enabled, it'll fail because you can
>> only enable all the FE_INVALID exceptions at once.
David> This straightforward extension to fenv.h sounds better to me also.
David> The fact that macros FE_DIVBYZERO, FE_INVALID, etc. exist fools many
David> people into thinking that they can be used as arguments to fesetenv to
David> effect the exception mask bits (as opposed to the status bits).
Here comes a patch for the feenableexcpt and fedisableexcpt functions.
Please note that I changed the semantics of the return value slightly
from Geoff's proposal.
I'll look at the "fast underflow" issue separatly, after we've agreed
on these functions.
Andreas
1999-10-27 Andreas Jaeger <aj@suse.de>
* math/fenv.h: Add prototypes for feenableexcept and
fedisableexcept.
* sysdeps/generic/feenablxcpt.c: Stub file.
* sysdeps/generic/fedisblxcpt.c: Stub file.
* sysdeps/i386/fpu/fedisblxcpt.c: New file.
* sysdeps/i386/fpu/feenablxcpt.c: New file.
* math/Makefile (libm-support): Add new files.
* math/Versions: Add new functions.
============================================================
Index: math/Makefile
--- math/Makefile 1999/10/19 06:28:01 1.89
+++ math/Makefile 1999/10/27 10:32:45
@@ -39,7 +39,7 @@
libm-support = k_standard s_lib_version s_matherr s_signgam \
fclrexcpt fgetexcptflg fraiseexcpt fsetexcptflg \
ftestexcept fegetround fesetround fegetenv feholdexcpt \
- fesetenv feupdateenv t_exp
+ fesetenv feupdateenv fedisblxcpt feenablxcpt t_exp
libm-calls = e_acos e_acosh e_asin e_atan2 e_atanh e_cosh e_exp e_fmod \
e_hypot e_j0 e_j1 e_jn e_lgamma_r e_log e_log10 e_pow \
e_rem_pio2 e_remainder e_scalb e_sinh e_sqrt e_gamma_r \
============================================================
Index: math/fenv.h
--- math/fenv.h 1999/10/19 03:04:54 1.5
+++ math/fenv.h 1999/10/27 10:32:46
@@ -109,6 +109,20 @@
according to saved exceptions. */
extern void feupdateenv (__const fenv_t *__envp) __THROW;
+#ifdef __USE_GNU
+/* Enable individual exceptions. Returns all enabled exceptions.
+ Will not enable more exceptions than EXCEPTS specifies. Returns 0
+ if EXCEPTS is not FE_ALL_EXCEPT and cannot enable or disable
+ exceptions individually. */
+extern int feenableexcept (int excepts) __THROW;
+
+/* Disable individual exceptions. Returns all enabled exceptions.
+ Will not disable more exceptions than EXCEPTS specifies. Returns 0
+ if EXCEPTS is not FE_ALL_EXCEPT and cannot enable or disable
+ exceptions individually. */
+extern int fedisableexcept (int excepts) __THROW;
+#endif
+
__END_DECLS
#endif /* fenv.h */
============================================================
Index: sysdeps/generic/feenablxcpt.c
--- sysdeps/generic/feenablxcpt.c created
+++ sysdeps/generic/feenablxcpt.c Wed Oct 27 12:11:16 1999 1.1
@@ -0,0 +1,29 @@
+/* Enable floating-point exceptions.
+ Copyright (C) 1999 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Andreas Jaeger <aj@suse.de>, 1999.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Library General Public License as
+ published by the Free Software Foundation; either version 2 of the
+ License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Library General Public License for more details.
+
+ You should have received a copy of the GNU Library General Public
+ License along with the GNU C Library; see the file COPYING.LIB. If not,
+ write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA. */
+
+#include <fenv.h>
+
+int
+feenableexcept (int excepts)
+{
+ return 0; /* Signal failure. */
+}
+stub_warning (feenableexcept)
+#include <stub-tag.h>
============================================================
Index: sysdeps/generic/fedisblxcpt.c
--- sysdeps/generic/fedisblxcpt.c created
+++ sysdeps/generic/fedisblxcpt.c Wed Oct 27 12:11:45 1999 1.1
@@ -0,0 +1,29 @@
+/* Disable floating-point exceptions.
+ Copyright (C) 1999 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Andreas Jaeger <aj@suse.de>, 1999.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Library General Public License as
+ published by the Free Software Foundation; either version 2 of the
+ License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Library General Public License for more details.
+
+ You should have received a copy of the GNU Library General Public
+ License along with the GNU C Library; see the file COPYING.LIB. If not,
+ write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA. */
+
+#include <fenv.h>
+
+int
+fedisableexcept (int excepts)
+{
+ return 0; /* Signal failure. */
+}
+stub_warning (fedisableexcept)
+#include <stub-tag.h>
============================================================
Index: sysdeps/i386/fpu/fedisblxcpt.c
--- sysdeps/i386/fpu/fedisblxcpt.c created
+++ sysdeps/i386/fpu/fedisblxcpt.c Wed Oct 27 12:31:09 1999 1.1
@@ -0,0 +1,37 @@
+/* Disable floating-point exceptions.
+ Copyright (C) 1999 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Andreas Jaeger <aj@suse.de>, 1999.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Library General Public License as
+ published by the Free Software Foundation; either version 2 of the
+ License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Library General Public License for more details.
+
+ You should have received a copy of the GNU Library General Public
+ License along with the GNU C Library; see the file COPYING.LIB. If not,
+ write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA. */
+
+#include <fenv.h>
+
+int
+fedisableexcept (int excepts)
+{
+ unsigned short int new_exc;
+
+ /* Get the current control word. */
+ __asm__ ("fstcw %0" : "=m" (*&new_exc));
+
+ excepts &= FE_ALL_EXCEPT;
+
+ new_exc &= ~excepts;
+ __asm__ ("fldcw %0" : : "m" (*&new_exc));
+
+ return new_exc & FE_ALL_EXCEPT;
+}
============================================================
Index: sysdeps/i386/fpu/feenablxcpt.c
--- sysdeps/i386/fpu/feenablxcpt.c created
+++ sysdeps/i386/fpu/feenablxcpt.c Wed Oct 27 12:31:14 1999 1.1
@@ -0,0 +1,36 @@
+/* Enable floating-point exceptions.
+ Copyright (C) 1999 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Andreas Jaeger <aj@suse.de>, 1999.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Library General Public License as
+ published by the Free Software Foundation; either version 2 of the
+ License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Library General Public License for more details.
+
+ You should have received a copy of the GNU Library General Public
+ License along with the GNU C Library; see the file COPYING.LIB. If not,
+ write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA. */
+
+#include <fenv.h>
+
+int
+feenableexcept (int excepts)
+{
+ unsigned short int new_exc;
+
+ /* Get the current control word. */
+ __asm__ ("fstcw %0" : "=m" (*&new_exc));
+
+ excepts &= FE_ALL_EXCEPT;
+ new_exc |= excepts;
+ __asm__ ("fldcw %0" : : "m" (*&new_exc));
+
+ return new_exc & FE_ALL_EXCEPT;
+}
============================================================
Index: math/Versions
--- math/Versions 1999/01/19 10:01:03 1.5
+++ math/Versions 1999/10/27 10:48:12
@@ -153,4 +153,9 @@
__fpclassify; __fpclassifyf; __fpclassifyl;
__signbit; __signbitf; __signbitl;
}
+
+ GLIBC_2.2 {
+ # fp environment function
+ feenableexcept; fedisableexcept;
+ }
}
--
Andreas Jaeger
SuSE Labs aj@suse.de
private aj@arthur.rhein-neckar.de