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.

1 files changed, 0 insertions, 6 deletions

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)