powerpc: Add redirection for finitef128, isinf128, and isnanf128

On powerpc64le, compiler support for float128 is not enabled by default
on gcc.  To enable it, the flag -mfloat128 must be passed as a command
line option to the compiler.  This means that only the few files that
actively have -mfloat128 passed as an argument get compiler support for
float128, whereas all other files don't.

When -mfloat128 becomes enabled by default on powerpc [1], all the files
that do not currently have compiler support for float128 enabled during
their compilation, will start to have it.  This will lead to build
errors in s_finite.c, s_isinf.c, and s_isnan.c.

The errors are due to the unintended macro expansion of __finitef128 to
__redirect_finitef128 in math/bits/mathcalls-helper-functions.h.  In
that header, __MATHDECL_1 takes '__finite' and 'f128' as arguments and
concatenates them.  However, since '__finite' has been redefined in
s_finite.c, the function declaration becomes __redirect_finitef128:

    extern int __redirect___finitef128 (_Float128 __value) __attribute__ ((__nothrow__ )) __attribute__ ((__const__));

This declaration itself is OK.  The problem arises when include/math.h
creates the hidden prototype ('hidden_proto (__finitef128)'), which
expands to:

    extern __typeof (__finitef128) __finitef128 __attribute__ ((visibility ("hidden")));

Since __finitef128 is not declared, __typeof fails.  This effect was
already true for the 'float' and 'long double' versions and is now true
for float128.  Likewise for isinsff128 and isnanf128.

This patch defines __finitef128 as __redirect___finitef128 in
sysdeps/powerpc/powerpc64/fpu/multiarch/s_finite.c, similarly to what's
done for the float and long double versions of these functions, to get
rid of the build error.  Likewise for isinff128 and isnanf128.

[1] https://gcc.gnu.org/ml/gcc-patches/2017-08/msg01028.html

Tested for powerpc64 and powerpc64le.

	* sysdeps/powerpc/powerpc64/fpu/multiarch/s_finite.c
	(__finitef128): Define to __redirect___finitef128.
	* sysdeps/powerpc/powerpc64/fpu/multiarch/s_isinf.c
	(__isinff128): Define to __redirect___isinff128.
	* sysdeps/powerpc/powerpc64/fpu/multiarch/s_isnan.c
	(__isnanf128): Define to __redirect___isnanf128.

1 files changed, 9 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 3a1f7a9..6dd3540 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,14 @@
 2017-09-21  Gabriel F. T. Gomes  <gabriel@inconstante.eti.br>
 
+	* sysdeps/powerpc/powerpc64/fpu/multiarch/s_finite.c
+	(__finitef128): Define to __redirect___finitef128.
+	* sysdeps/powerpc/powerpc64/fpu/multiarch/s_isinf.c
+	(__isinff128): Define to __redirect___isinff128.
+	* sysdeps/powerpc/powerpc64/fpu/multiarch/s_isnan.c
+	(__isnanf128): Define to __redirect___isnanf128.
+
+2017-09-21  Gabriel F. T. Gomes  <gabriel@inconstante.eti.br>
+
 	* sysdeps/powerpc/powerpc64le/Makefile
 	(CFLAGS-tst-strtod-nan-locale.c): New variable.
 	(CFLAGS-tst-wcstod-nan-locale.c): New variable.