Add support for sqrt asm redirects

This patch series cleans up the many uses of  __ieee754_sqrt(f/l) in GLIBC.
The goal is to enable GCC to do the inlining, and if this fails call the
__ieee754_sqrt function.  This is done by internally declaring sqrt with asm
redirects.  The compat symbols and sqrt wrappers need to disable the redirect.
The redirect is also disabled if there are already redirects defined when
using -ffinite-math-only.

All math functions (but not math tests, non-library code and libnldbl) are
built with -fno-math-errno which means GCC will typically inline sqrt as a
single instruction.  This means targets are no longer forced to add a special
inline for sqrt.

	* include/math.h (sqrt): Declare with asm redirect.
	(sqrtf): Likewise.
	(sqrtl): Likewise.
	(sqrtf128): Likewise.
	* Makeconfig: Add -fno-math-errno for libc/libm, but build testsuite,
	nonlib and libnldbl with -fmath-errno.
	* math/w_sqrt_compat.c: Define NO_MATH_REDIRECT.
	* math/w_sqrt_template.c: Likewise.
	* math/w_sqrtf_compat.c: Likewise.
	* math/w_sqrtl_compat.c: Likewise.
	* sysdeps/i386/fpu/w_sqrt.c: Likewise.
	* sysdeps/i386/fpu/w_sqrt_compat.c: Likewise.
	* sysdeps/generic/math-type-macros-float128.h: Remove math.h and
	complex.h.

ChangeLog

@@ -25,6 +25,23 @@
 	[__USE_ISOC99] (llrintf): Likewise.
 	[__USE_ISOC99] (llrintl): Likewise.
 
+2018-03-15  Wilco Dijkstra  <wdijkstr@arm.com>
+
+	* include/math.h (sqrt): Declare with asm redirect.
+	(sqrtf): Likewise.
+	(sqrtl): Likewise.
+	(sqrtf128): Likewise.
+	* Makeconfig: Add -fno-math-errno for libc/libm, but build testsuite,
+	nonlib and libnldbl with -fmath-errno.
+	* math/w_sqrt_compat.c: Define NO_MATH_REDIRECT.
+	* math/w_sqrt_template.c: Likewise.
+	* math/w_sqrtf_compat.c: Likewise.
+	* math/w_sqrtl_compat.c: Likewise.
+	* sysdeps/i386/fpu/w_sqrt.c: Likewise.
+	* sysdeps/i386/fpu/w_sqrt_compat.c: Likewise.
+	* sysdeps/generic/math-type-macros-float128.h: Remove math.h and
+	complex.h.
+
 2018-03-15  Wilco Dijkstra  <wdijkstr@arm.com>
 
 	* benchtests/Makefile: Define _ISOMAC.

Makeconfig

@@ -831,6 +831,9 @@ endif
 # disable any optimization that assume default rounding mode.
 +math-flags = -frounding-math
 
+# Build libc/libm using -fno-math-errno, but run testsuite with -fmath-errno.
++extra-math-flags = $(if $(filter libnldbl nonlib testsuite,$(in-module)),-fmath-errno,-fno-math-errno)
+
 # We might want to compile with some stack-protection flag.
 ifneq ($(stack-protector),)
 +stack-protector=$(stack-protector)
@@ -966,6 +969,7 @@ endif
 
 override CFLAGS	= -std=gnu11 -fgnu89-inline $(config-extra-cflags) \
 		  $(filter-out %frame-pointer,$(+cflags)) $(+gccwarn-c) \
+		  $(+extra-math-flags) \
 		  $(sysdep-CFLAGS) $(CFLAGS-$(suffix $@)) $(CFLAGS-$(<F)) \
 		  $(CFLAGS-$(@F)) $(tls-model) \
 		  $(foreach lib,$(libof-$(basename $(@F))) \

include/math.h

@@ -54,5 +54,20 @@ libm_hidden_proto (__expf128)
 libm_hidden_proto (__expm1f128)
 # endif
 
+# if !(defined __FINITE_MATH_ONLY__ && __FINITE_MATH_ONLY__ > 0)
+#  ifndef NO_MATH_REDIRECT
+/* Declare sqrt for use within GLIBC.  Compilers typically inline sqrt as a
+   single instruction.  Use an asm to avoid use of PLTs if it doesn't.  */
+float (sqrtf) (float) asm ("__ieee754_sqrtf");
+double (sqrt) (double) asm ("__ieee754_sqrt");
+#   ifndef __NO_LONG_DOUBLE_MATH
+long double (sqrtl) (long double) asm ("__ieee754_sqrtl");
+#   endif
+#   if __HAVE_DISTINCT_FLOAT128 > 0
+_Float128 (sqrtf128) (_Float128) asm ("__ieee754_sqrtf128");
+#   endif
+#  endif
+# endif
+
 #endif
 #endif

math/w_sqrt_compat.c

@@ -16,6 +16,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#define NO_MATH_REDIRECT
 #include <math.h>
 #include <math_private.h>
 #include <math-svid-compat.h>

math/w_sqrt_template.c

@@ -21,6 +21,7 @@
    for each floating-point type.  */
 #if __USE_WRAPPER_TEMPLATE
 
+# define NO_MATH_REDIRECT
 # include <errno.h>
 # include <fenv.h>
 # include <math.h>

math/w_sqrtf_compat.c

@@ -16,6 +16,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#define NO_MATH_REDIRECT
 #include <math.h>
 #include <math_private.h>
 #include <math-svid-compat.h>

math/w_sqrtl_compat.c

@@ -16,6 +16,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#define NO_MATH_REDIRECT
 #include <math.h>
 #include <math_private.h>
 #include <math-svid-compat.h>

sysdeps/generic/math-type-macros-float128.h

@@ -19,9 +19,6 @@
 #ifndef _MATH_TYPE_MACROS_FLOAT128
 #define _MATH_TYPE_MACROS_FLOAT128
 
-#include <math.h>
-#include <complex.h>
-
 #define M_LIT(c) __f128 (c)
 #define M_PFX FLT128
 #define M_SUF(c) c ## f128

sysdeps/i386/fpu/w_sqrt.c

@@ -1,5 +1,6 @@
 /* The inline __ieee754_sqrt is not correctly rounding; it's OK for
    most internal uses in glibc, but not for sqrt itself.  */
+#define NO_MATH_REDIRECT
 #define __ieee754_sqrt __avoid_ieee754_sqrt
 #include <math.h>
 #include <math_private.h>

sysdeps/i386/fpu/w_sqrt_compat.c

@@ -1,5 +1,6 @@
 /* The inline __ieee754_sqrt is not correctly rounding; it's OK for
    most internal uses in glibc, but not for sqrt itself.  */
+#define NO_MATH_REDIRECT
 #define __ieee754_sqrt __avoid_ieee754_sqrt
 #include <math.h>
 #include <math_private.h>