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.

16 files changed, 82 insertions, 83 deletions

diff --git a/sysdeps/aarch64/bits/mathdef.h b/sysdeps/aarch64/bits/mathdef.h
index db992fccc1..2b55b59a5e 100644
--- a/sysdeps/aarch64/bits/mathdef.h
+++ b/sysdeps/aarch64/bits/mathdef.h
@@ -23,12 +23,6 @@
 #if defined  __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* GCC does not promote `float' values to `double'.  */
-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)
diff --git a/sysdeps/alpha/bits/mathdef.h b/sysdeps/alpha/bits/mathdef.h
index ed70ad8dbd..fbca194a78 100644
--- a/sysdeps/alpha/bits/mathdef.h
+++ b/sysdeps/alpha/bits/mathdef.h
@@ -25,10 +25,6 @@
 #if defined __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* Alpha has "float" and "double" operations.  */
-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)
diff --git a/sysdeps/arm/bits/mathdef.h b/sysdeps/arm/bits/mathdef.h
index ae0bcb7bf5..68c96f0ce4 100644
--- a/sysdeps/arm/bits/mathdef.h
+++ b/sysdeps/arm/bits/mathdef.h
@@ -22,12 +22,6 @@
 #if defined  __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* GCC does not promote `float' values to `double'.  */
-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)
diff --git a/sysdeps/hppa/fpu/bits/mathdef.h b/sysdeps/hppa/fpu/bits/mathdef.h
index 99c9cffd25..24b67b2f62 100644
--- a/sysdeps/hppa/fpu/bits/mathdef.h
+++ b/sysdeps/hppa/fpu/bits/mathdef.h
@@ -22,12 +22,6 @@
 #if defined  __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* GCC does not promote `float' values to `double'.  */
-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)
diff --git a/sysdeps/ia64/bits/mathdef.h b/sysdeps/ia64/bits/mathdef.h
index 5a31bd3db7..44a7642342 100644
--- a/sysdeps/ia64/bits/mathdef.h
+++ b/sysdeps/ia64/bits/mathdef.h
@@ -22,13 +22,6 @@
 #if defined __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* The IA-64 architecture computes values with the precision of the
-   used 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 - 1)
 # define FP_ILOGBNAN	2147483647
diff --git a/sysdeps/m68k/m680x0/bits/flt-eval-method.h b/sysdeps/m68k/m680x0/bits/flt-eval-method.h
new file mode 100644
index 0000000000..b2a38acabb
--- /dev/null
+++ b/sysdeps/m68k/m680x0/bits/flt-eval-method.h
@@ -0,0 +1,25 @@
+/* Define __GLIBC_FLT_EVAL_METHOD.  M68K version.
+   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
+
+/* The m68k FPUs evaluate all values in the 96-bit floating-point
+   format which is also available for the user as 'long double'.  */
+#define __GLIBC_FLT_EVAL_METHOD	2
diff --git a/sysdeps/m68k/m680x0/bits/mathdef.h b/sysdeps/m68k/m680x0/bits/mathdef.h
index a5509384c4..702bd0e33a 100644
--- a/sysdeps/m68k/m680x0/bits/mathdef.h
+++ b/sysdeps/m68k/m680x0/bits/mathdef.h
@@ -22,14 +22,6 @@
 #if defined __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* The m68k FPUs evaluate all values in the 96 bit floating-point format
-   which is also available for the user as `long double'.  Therefore we
-   define: */
-typedef long double float_t;	/* `float' expressions are evaluated as
-				   `long double'.  */
-typedef long double double_t;	/* `double' expressions are evaluated as
-				   `long double'.  */
-
 /* The values returned by `ilogb' for 0 and NaN respectively.  */
 # define FP_ILOGB0	(-2147483647 - 1)
 # define FP_ILOGBNAN	(2147483647)
diff --git a/sysdeps/mips/bits/mathdef.h b/sysdeps/mips/bits/mathdef.h
index 3a1162776f..74abf97ea3 100644
--- a/sysdeps/mips/bits/mathdef.h
+++ b/sysdeps/mips/bits/mathdef.h
@@ -24,12 +24,6 @@
 #if defined  __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* MIPS has `float' and `double' operations.  */
-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
diff --git a/sysdeps/powerpc/bits/mathdef.h b/sysdeps/powerpc/bits/mathdef.h
index d4dd4b5c6a..debb5a5d26 100644
--- a/sysdeps/powerpc/bits/mathdef.h
+++ b/sysdeps/powerpc/bits/mathdef.h
@@ -29,10 +29,6 @@
 #if defined __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* PowerPC has both `float' and `double' arithmetic.  */
-typedef float float_t;
-typedef double double_t;
-
 /* The values returned by `ilogb' for 0 and NaN respectively.  */
 # define FP_ILOGB0	(-2147483647)
 # define FP_ILOGBNAN	(2147483647)
diff --git a/sysdeps/s390/bits/flt-eval-method.h b/sysdeps/s390/bits/flt-eval-method.h
new file mode 100644
index 0000000000..5793175fc5
--- /dev/null
+++ b/sysdeps/s390/bits/flt-eval-method.h
@@ -0,0 +1,24 @@
+/* Define __GLIBC_FLT_EVAL_METHOD.  S/390 version.
+   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
+
+/* This value is used because of a historical mistake.  */
+#define __GLIBC_FLT_EVAL_METHOD	1
diff --git a/sysdeps/s390/bits/mathdef.h b/sysdeps/s390/bits/mathdef.h
index 8c47ade208..5ad04aecef 100644
--- a/sysdeps/s390/bits/mathdef.h
+++ b/sysdeps/s390/bits/mathdef.h
@@ -22,13 +22,6 @@
 #if defined  __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* Normally, there is no long double type and the `float' and `double'
-   expressions are evaluated as `double'.  */
-typedef double float_t;		/* `float' expressions are evaluated as
-				   `double'.  */
-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
diff --git a/sysdeps/sh/sh4/bits/mathdef.h b/sysdeps/sh/sh4/bits/mathdef.h
index 21ce094533..f3ee2879a7 100644
--- a/sysdeps/sh/sh4/bits/mathdef.h
+++ b/sysdeps/sh/sh4/bits/mathdef.h
@@ -29,10 +29,6 @@
 #if defined __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* SH has both `float' and `double' arithmetic.  */
-typedef float float_t;
-typedef double double_t;
-
 /* The values returned by `ilogb' for 0 and NaN respectively.  */
 # define FP_ILOGB0	(-0x7fffffff)
 # define FP_ILOGBNAN	0x7fffffff
diff --git a/sysdeps/sparc/bits/mathdef.h b/sysdeps/sparc/bits/mathdef.h
index 94a102a1d4..55a35306ce 100644
--- a/sysdeps/sparc/bits/mathdef.h
+++ b/sysdeps/sparc/bits/mathdef.h
@@ -27,10 +27,6 @@
 #if defined __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* SPARC has both `float' and `double' arithmetic.  */
-typedef float float_t;
-typedef double double_t;
-
 /* The values returned by `ilogb' for 0 and NaN respectively.  */
 # define FP_ILOGB0       (-2147483647)
 # define FP_ILOGBNAN     (2147483647)
diff --git a/sysdeps/tile/bits/mathdef.h b/sysdeps/tile/bits/mathdef.h
index 2db81b46ea..8ed7ac4341 100644
--- a/sysdeps/tile/bits/mathdef.h
+++ b/sysdeps/tile/bits/mathdef.h
@@ -23,10 +23,6 @@
 #if defined __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-/* "float" and "double" expressions evaluated as "float" and "double". */
-typedef float float_t;
-typedef double double_t;
-
 /* The values returned by `ilogb' for 0 and NaN respectively.  */
 # define FP_ILOGB0	(-2147483647)
 # define FP_ILOGBNAN	(2147483647)
diff --git a/sysdeps/x86/bits/flt-eval-method.h b/sysdeps/x86/bits/flt-eval-method.h
new file mode 100644
index 0000000000..674f2fcc05
--- /dev/null
+++ b/sysdeps/x86/bits/flt-eval-method.h
@@ -0,0 +1,33 @@
+/* Define __GLIBC_FLT_EVAL_METHOD.  x86 version.
+   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
+
+#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
+#elif defined __x86_64__
+# define __GLIBC_FLT_EVAL_METHOD	0
+#else
+# define __GLIBC_FLT_EVAL_METHOD	2
+#endif
diff --git a/sysdeps/x86/bits/mathdef.h b/sysdeps/x86/bits/mathdef.h
index 9423a7f558..2f0025c38d 100644
--- a/sysdeps/x86/bits/mathdef.h
+++ b/sysdeps/x86/bits/mathdef.h
@@ -22,23 +22,6 @@
 #if defined __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF
 # define _MATH_H_MATHDEF	1
 
-# if ((defined __x86_64__ && !defined __FLT_EVAL_METHOD__)		\
-      || (defined __FLT_EVAL_METHOD__ && __FLT_EVAL_METHOD__ == 0))
-/* The x86-64 architecture computes values with the precission of the
-   used type.  Similarly for -m32 -mfpmath=sse.  */
-typedef float float_t;		/* `float' expressions are evaluated as `float'.  */
-typedef double double_t;	/* `double' expressions are evaluated
-				   as `double'.  */
-# else
-/* The ix87 FPUs evaluate all values in the 80 bit floating-point format
-   which is also available for the user as `long double'.  Therefore we
-   define:  */
-typedef long double float_t;	/* `float' expressions are evaluated as
-				   `long double'.  */
-typedef long double double_t;	/* `double' expressions are evaluated as
-				   `long double'.  */
-# endif
-
 /* The values returned by `ilogb' for 0 and NaN respectively.  */
 # define FP_ILOGB0	(-2147483647 - 1)
 # define FP_ILOGBNAN	(-2147483647 - 1)