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.

ChangeLog

@@ -1,3 +1,12 @@
+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

sysdeps/powerpc/powerpc64/fpu/multiarch/s_finite.c

@@ -17,8 +17,16 @@
    <http://www.gnu.org/licenses/>.  */
 
 #define __finite __redirect___finite
+
+/* The following definitions, although not related to the 'double'
+   version of 'finite', are required to guarantee macro expansions
+   (e.g.: from __finitef to __redirect_finitef) in include/math.h, thus
+   compensating for the unintended macro expansions in
+   math/bits/mathcalls-helper-functions.h.  */
 #define __finitef __redirect___finitef
 #define __finitel __redirect___finitel
+#define __finitef128 __redirect___finitef128
+
 #include <math.h>
 #include <math_ldbl_opt.h>
 #include <shlib-compat.h>
@@ -30,6 +38,7 @@ extern __typeof (__finite) __finite_power8 attribute_hidden;
 #undef __finite
 #undef __finitef
 #undef __finitel
+#undef __finitef128
 
 libc_ifunc_redirected (__redirect___finite, __finite,
 		       (hwcap2 & PPC_FEATURE2_ARCH_2_07)

sysdeps/powerpc/powerpc64/fpu/multiarch/s_isinf.c

@@ -17,8 +17,16 @@
    <http://www.gnu.org/licenses/>.  */
 
 #define __isinf __redirect___isinf
+
+/* The following definitions, although not related to the 'double'
+   version of 'isinf', are required to guarantee macro expansions
+   (e.g.: from __isinff to __redirect_isinff) in include/math.h, thus
+   compensating for the unintended macro expansions in
+   math/bits/mathcalls-helper-functions.h.  */
 #define __isinff __redirect___isinff
 #define __isinfl __redirect___isinfl
+#define __isinff128 __redirect___isinff128
+
 #include <math.h>
 #include <math_ldbl_opt.h>
 #include <shlib-compat.h>
@@ -30,6 +38,7 @@ extern __typeof (__isinf) __isinf_power8 attribute_hidden;
 #undef __isinf
 #undef __isinff
 #undef __isinfl
+#undef __isinff128
 
 libc_ifunc_redirected (__redirect___isinf, __isinf,
 		       (hwcap2 & PPC_FEATURE2_ARCH_2_07)

sysdeps/powerpc/powerpc64/fpu/multiarch/s_isnan.c

@@ -17,8 +17,16 @@
    <http://www.gnu.org/licenses/>.  */
 
 #define __isnan __redirect___isnan
+
+/* The following definitions, although not related to the 'double'
+   version of 'isnan', are required to guarantee macro expansions
+   (e.g.: from __isnanf to __redirect_isnanf) in include/math.h, thus
+   compensating for the unintended macro expansions in
+   math/bits/mathcalls-helper-functions.h.  */
 #define __isnanf __redirect___isnanf
 #define __isnanl __redirect___isnanl
+#define __isnanf128 __redirect___isnanf128
+
 #include <math.h>
 #include <math_ldbl_opt.h>
 #include <shlib-compat.h>
@@ -33,6 +41,7 @@ extern __typeof (__isnan) __isnan_power8 attribute_hidden;
 #undef __isnan
 #undef __isnanf
 #undef __isnanl
+#undef __isnanf128
 
 libc_ifunc_redirected (__redirect___isnan, __isnan,
 		       (hwcap2 & PPC_FEATURE2_ARCH_2_07)