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authorJoseph Myers <joseph@codesourcery.com>2016-11-24 18:44:50 +0000
committerJoseph Myers <joseph@codesourcery.com>2016-11-24 18:44:50 +0000
commit93eb85ceb25ee7aff432ddea0abf559f53d7a5fc (patch)
tree7f3fa3024190dfadcda7c249e8b33e19e8b52128 /bits
parent380ec16d62f459d5a28cfc25b7b20990c45e1cc9 (diff)
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Refactor float_t, double_t information into bits/flt-eval-method.h.
At present, definitions of float_t and double_t are split among many bits/mathdef.h headers. For all but three architectures, these types are float and double. Furthermore, if you assume __FLT_EVAL_METHOD__ to be defined, that provides a more generic way of determining the correct values of these typedefs. Defining these typedefs more generally based on __FLT_EVAL_METHOD__ was previously proposed by Paul Eggert in <https://sourceware.org/ml/libc-alpha/2012-02/msg00002.html>. This patch refactors things in the way I proposed in <https://sourceware.org/ml/libc-alpha/2016-11/msg00745.html>. A new header bits/flt-eval-method.h defines a single macro, __GLIBC_FLT_EVAL_METHOD, which is then used by math.h to define float_t and double_t. The default is based on __FLT_EVAL_METHOD__ (although actually a default to 0 would have the same effect for current ports, because ports where values other than 0 or 16 are possible all have their own headers). To avoid changing the existing semantics in any case, including for compilers not defining __FLT_EVAL_METHOD__, architecture-specific files are then added for m68k, s390, x86 which replicate the existing semantics. At least with __FLT_EVAL_METHOD__ values possible with GCC, there should be no change to the choices of float_t and double_t for any supported configuration. Architecture maintainer notes: * m68k: sysdeps/m68k/m680x0/bits/flt-eval-method.h always defines __GLIBC_FLT_EVAL_METHOD to 2 to replicate the existing logic. But actually GCC defines __FLT_EVAL_METHOD__ to 0 if TARGET_68040. It might make sense to make the header prefer to base things on __FLT_EVAL_METHOD__ if defined, like the x86 version, and so make the choices of these types more accurate (with a NEWS entry as for the other changes to these types on particular architectures). * s390: sysdeps/s390/bits/flt-eval-method.h always defines __GLIBC_FLT_EVAL_METHOD to 1 to replicate the existing logic. As previously discussed, it might make sense in coordination with GCC to eliminate the historic mistake, avoid excess precision in the -fexcess-precision=standard case and make the typedefs match (with a NEWS entry, again). Tested for x86-64 and x86. Also did compilation-only testing with build-many-glibcs.py. * bits/flt-eval-method.h: New file. * sysdeps/m68k/m680x0/bits/flt-eval-method.h: Likewise. * sysdeps/s390/bits/flt-eval-method.h: Likewise. * sysdeps/x86/bits/flt-eval-method.h: Likewise. * math/Makefile (headers): Add bits/flt-eval-method.h. * math/math.h: Include <bits/flt-eval-method.h>. [__USE_ISOC99] (float_t): Define based on __GLIBC_FLT_EVAL_METHOD. [__USE_ISOC99] (double_t): Likewise. * bits/mathdef.h (float_t): Remove. (double_t): Likewise. * sysdeps/aarch64/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/alpha/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/arm/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/hppa/fpu/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/ia64/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/m68k/m680x0/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/mips/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/powerpc/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/s390/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/sh/sh4/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/sparc/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/tile/bits/mathdef.h (float_t): Likewise. (double_t): Likewise. * sysdeps/x86/bits/mathdef.h (float_t): Likewise. (double_t): Likewise.
Diffstat (limited to 'bits')
-rw-r--r--bits/flt-eval-method.h42
-rw-r--r--bits/mathdef.h7
2 files changed, 42 insertions, 7 deletions
diff --git a/bits/flt-eval-method.h b/bits/flt-eval-method.h
new file mode 100644
index 0000000000..8ecd6a6664
--- /dev/null
+++ b/bits/flt-eval-method.h
@@ -0,0 +1,42 @@
+/* Define __GLIBC_FLT_EVAL_METHOD.
+ Copyright (C) 2016 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _MATH_H
+# error "Never use <bits/flt-eval-method.h> directly; include <math.h> instead."
+#endif
+
+/* __GLIBC_FLT_EVAL_METHOD is the value of FLT_EVAL_METHOD used to
+ determine the evaluation method typedefs such as float_t and
+ double_t. It must be a value from C11 or TS 18661-3:2015, and not
+ -1. */
+
+/* In the default version of this header, follow __FLT_EVAL_METHOD__.
+ -1 is mapped to 2 (considering evaluation as long double to be a
+ conservatively safe assumption), and if __FLT_EVAL_METHOD__ is not
+ defined then assume there is no excess precision and use the value
+ 0. */
+
+#ifdef __FLT_EVAL_METHOD__
+# if __FLT_EVAL_METHOD__ == -1
+# define __GLIBC_FLT_EVAL_METHOD 2
+# else
+# define __GLIBC_FLT_EVAL_METHOD __FLT_EVAL_METHOD__
+# endif
+#else
+# define __GLIBC_FLT_EVAL_METHOD 0
+#endif
diff --git a/bits/mathdef.h b/bits/mathdef.h
index d557d08582..6dedc51c83 100644
--- a/bits/mathdef.h
+++ b/bits/mathdef.h
@@ -22,13 +22,6 @@
#if defined __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
# define _MATH_H_MATHDEF 1
-/* Expressions are evaluated with the range and precision of their
- type. */
-typedef float float_t; /* `float' expressions are evaluated as
- `float'. */
-typedef double double_t; /* `double' expressions are evaluated as
- `double'. */
-
/* The values returned by `ilogb' for 0 and NaN respectively. */
# define FP_ILOGB0 (-2147483647)
# define FP_ILOGBNAN 2147483647