Add narrowing add functions.

This patch adds the narrowing add functions from TS 18661-1 to glibc's
libm: fadd, faddl, daddl, f32addf64, f32addf32x, f32xaddf64 for all
configurations; f32addf64x, f32addf128, f64addf64x, f64addf128,
f32xaddf64x, f32xaddf128, f64xaddf128 for configurations with
_Float64x and _Float128; __nldbl_daddl for ldbl-opt.  As discussed for
the build infrastructure patch, tgmath.h support is deliberately
deferred, and FP_FAST_* macros are not applicable without optimized
function implementations.

Function implementations are added for all relevant pairs of formats
(including certain cases of a format and itself where more than one
type has that format).  The main implementations use round-to-odd, or
a trivial computation in the case where both formats are the same or
where the wider format is IBM long double (in which case we don't
attempt to be correctly rounding).  The sysdeps/ieee754/soft-fp
implementations use soft-fp, and are used automatically for
configurations without exceptions and rounding modes by virtue of
existing Implies files.  As previously discussed, optimized versions
for particular architectures are possible, but not included.

i386 gets a special version of f32xaddf64 to avoid problems with
double rounding (similar to the existing fdim version), since this
function must round just once without an intermediate rounding to long
double.  (No such special version is needed for any other function,
because the nontrivial functions use round-to-odd, which does the
intermediate computation with the rounding mode set to round-to-zero,
and double rounding is OK except in round-to-nearest mode, so is OK
for that intermediate round-to-zero computation.)  mul and div will
need slightly different special versions for i386 (using round-to-odd
on long double instead of precision control) because of the
possibility of inexact intermediate results in the subnormal range for
double.

To reduce duplication among the different function implementations,
math-narrow.h gets macros CHECK_NARROW_ADD, NARROW_ADD_ROUND_TO_ODD
and NARROW_ADD_TRIVIAL.

In the trivial cases and for any architecture-specific optimized
implementations, the overhead of the errno setting might be
significant, but I think that's best handled through compiler built-in
functions rather than providing separate no-errno versions in glibc
(and likewise there are no __*_finite entry points for these function
provided, __*_finite effectively being no-errno versions at present in
most cases).

Tested for x86_64 and x86, with both GCC 6 and GCC 7.  Tested for
mips64 (all three ABIs, both hard and soft float) and powerpc with GCC
7.  Tested with build-many-glibcs.py with both GCC 6 and GCC 7.

	* math/Makefile (libm-narrow-fns): Add add.
	(libm-test-funcs-narrow): Likewise.
	* math/Versions (GLIBC_2.28): Add narrowing add functions.
	* math/bits/mathcalls-narrow.h (add): Use __MATHCALL_NARROW .
	* math/gen-auto-libm-tests.c (test_functions): Add add.
	* math/math-narrow.h (CHECK_NARROW_ADD): New macro.
	(NARROW_ADD_ROUND_TO_ODD): Likewise.
	(NARROW_ADD_TRIVIAL): Likewise.
	* sysdeps/ieee754/float128/float128_private.h (__faddl): New
	macro.
	(__daddl): Likewise.
	* sysdeps/ieee754/ldbl-opt/Makefile (libnldbl-calls): Add fadd and
	dadd.
	(CFLAGS-nldbl-dadd.c): New variable.
	(CFLAGS-nldbl-fadd.c): Likewise.
	* sysdeps/ieee754/ldbl-opt/Versions (GLIBC_2.28): Add
	__nldbl_daddl.
	* sysdeps/ieee754/ldbl-opt/nldbl-compat.h (__nldbl_daddl): New
	prototype.
	* manual/arith.texi (Misc FP Arithmetic): Document fadd, faddl,
	daddl, fMaddfN, fMaddfNx, fMxaddfN and fMxaddfNx.
	* math/auto-libm-test-in: Add tests of add.
	* math/auto-libm-test-out-narrow-add: New generated file.
	* math/libm-test-narrow-add.inc: New file.
	* sysdeps/i386/fpu/s_f32xaddf64.c: Likewise.
	* sysdeps/ieee754/dbl-64/s_f32xaddf64.c: Likewise.
	* sysdeps/ieee754/dbl-64/s_fadd.c: Likewise.
	* sysdeps/ieee754/float128/s_f32addf128.c: Likewise.
	* sysdeps/ieee754/float128/s_f64addf128.c: Likewise.
	* sysdeps/ieee754/float128/s_f64xaddf128.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_daddl.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_f64xaddf128.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_faddl.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_daddl.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_faddl.c: Likewise.
	* sysdeps/ieee754/ldbl-96/s_daddl.c: Likewise.
	* sysdeps/ieee754/ldbl-96/s_faddl.c: Likewise.
	* sysdeps/ieee754/ldbl-opt/nldbl-dadd.c: Likewise.
	* sysdeps/ieee754/ldbl-opt/nldbl-fadd.c: Likewise.
	* sysdeps/ieee754/soft-fp/s_daddl.c: Likewise.
	* sysdeps/ieee754/soft-fp/s_fadd.c: Likewise.
	* sysdeps/ieee754/soft-fp/s_faddl.c: Likewise.
	* sysdeps/powerpc/fpu/libm-test-ulps: Update.
	* sysdeps/mach/hurd/i386/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/aarch64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/alpha/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/arm/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/hppa/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/i386/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/ia64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/m68k/coldfire/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/m68k/m680x0/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/microblaze/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips32/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/nios2/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libm-le.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/riscv/rv64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sh/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/tile/tilegx32/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/tile/tilegx64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/64/libm.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/x32/libm.abilist: Likewise.

21 files changed, 549 insertions, 1 deletions

diff --git a/sysdeps/ieee754/dbl-64/s_f32xaddf64.c b/sysdeps/ieee754/dbl-64/s_f32xaddf64.c
new file mode 100644
index 0000000000..6e20a9e939
--- /dev/null
+++ b/sysdeps/ieee754/dbl-64/s_f32xaddf64.c
@@ -0,0 +1,30 @@
+/* Add _Float64 values, converting the result to _Float32x.
+   Copyright (C) 2018 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/>.  */
+
+#define daddl __hide_daddl
+#include <math.h>
+#undef daddl
+
+#include <math-narrow.h>
+
+_Float32x
+__f32xaddf64 (_Float64 x, _Float64 y)
+{
+  NARROW_ADD_TRIVIAL (x, y, _Float32x);
+}
+libm_alias_float32x_float64 (add)
diff --git a/sysdeps/ieee754/dbl-64/s_fadd.c b/sysdeps/ieee754/dbl-64/s_fadd.c
new file mode 100644
index 0000000000..5ecb435497
--- /dev/null
+++ b/sysdeps/ieee754/dbl-64/s_fadd.c
@@ -0,0 +1,34 @@
+/* Add double values, narrowing the result to float.
+   Copyright (C) 2018 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/>.  */
+
+#define f32addf64 __hide_f32addf64
+#define f32addf32x __hide_f32addf32x
+#define faddl __hide_faddl
+#include <math.h>
+#undef f32addf64
+#undef f32addf32x
+#undef faddl
+
+#include <math-narrow.h>
+
+float
+__fadd (double x, double y)
+{
+  NARROW_ADD_ROUND_TO_ODD (x, y, float, union ieee754_double, , mantissa1);
+}
+libm_alias_float_double (add)
diff --git a/sysdeps/ieee754/float128/float128_private.h b/sysdeps/ieee754/float128/float128_private.h
index d0d41c3cef..eebf19af93 100644
--- a/sysdeps/ieee754/float128/float128_private.h
+++ b/sysdeps/ieee754/float128/float128_private.h
@@ -256,6 +256,9 @@
 #define __truncl __truncf128
 #define __x2y2m1l __x2y2m1f128
 
+#define __faddl __f32addf128
+#define __daddl __f64addf128
+
 /* __nexttowardf128 is not _Float128 API. */
 #define __nexttowardl __nexttowardf128_do_not_use
 #define nexttowardl nexttowardf128_do_not_use
diff --git a/sysdeps/ieee754/float128/s_f32addf128.c b/sysdeps/ieee754/float128/s_f32addf128.c
new file mode 100644
index 0000000000..e2f8ded401
--- /dev/null
+++ b/sysdeps/ieee754/float128/s_f32addf128.c
@@ -0,0 +1,6 @@
+#define f32addf64x __hide_f32addf64x
+#define f32addf128 __hide_f32addf128
+#include <float128_private.h>
+#undef f32addf64x
+#undef f32addf128
+#include "../ldbl-128/s_faddl.c"
diff --git a/sysdeps/ieee754/float128/s_f64addf128.c b/sysdeps/ieee754/float128/s_f64addf128.c
new file mode 100644
index 0000000000..c2bb293399
--- /dev/null
+++ b/sysdeps/ieee754/float128/s_f64addf128.c
@@ -0,0 +1,10 @@
+#define f32xaddf64x __hide_f32xaddf64x
+#define f32xaddf128 __hide_f32xaddf128
+#define f64addf64x __hide_f64addf64x
+#define f64addf128 __hide_f64addf128
+#include <float128_private.h>
+#undef f32xaddf64x
+#undef f32xaddf128
+#undef f64addf64x
+#undef f64addf128
+#include "../ldbl-128/s_daddl.c"
diff --git a/sysdeps/ieee754/float128/s_f64xaddf128.c b/sysdeps/ieee754/float128/s_f64xaddf128.c
new file mode 100644
index 0000000000..c8af0a5dff
--- /dev/null
+++ b/sysdeps/ieee754/float128/s_f64xaddf128.c
@@ -0,0 +1,2 @@
+#include <float128_private.h>
+#include "../ldbl-128/s_f64xaddf128.c"
diff --git a/sysdeps/ieee754/ldbl-128/s_daddl.c b/sysdeps/ieee754/ldbl-128/s_daddl.c
new file mode 100644
index 0000000000..81e8e2d3e1
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128/s_daddl.c
@@ -0,0 +1,37 @@
+/* Add long double (ldbl-128) values, narrowing the result to double.
+   Copyright (C) 2018 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/>.  */
+
+#define f32xaddf64x __hide_f32xaddf64x
+#define f32xaddf128 __hide_f32xaddf128
+#define f64addf64x __hide_f64addf64x
+#define f64addf128 __hide_f64addf128
+#include <math.h>
+#undef f32xaddf64x
+#undef f32xaddf128
+#undef f64addf64x
+#undef f64addf128
+
+#include <math-narrow.h>
+
+double
+__daddl (_Float128 x, _Float128 y)
+{
+  NARROW_ADD_ROUND_TO_ODD (x, y, double, union ieee854_long_double, l,
+			   mantissa3);
+}
+libm_alias_double_ldouble (add)
diff --git a/sysdeps/ieee754/ldbl-128/s_f64xaddf128.c b/sysdeps/ieee754/ldbl-128/s_f64xaddf128.c
new file mode 100644
index 0000000000..545c7b93fd
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128/s_f64xaddf128.c
@@ -0,0 +1,38 @@
+/* Add _Float128 values, converting the result to _Float64x.
+   Copyright (C) 2018 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/>.  */
+
+#include <math.h>
+#include <math-narrow.h>
+
+/* math_ldbl.h defines _Float128 to long double for this directory,
+   but when they are different, this function must be defined with
+   _Float128 arguments to avoid defining an alias with an incompatible
+   type.  */
+#undef _Float128
+
+_Float64x
+__f64xaddf128 (_Float128 x, _Float128 y)
+{
+#if __HAVE_FLOAT64X_LONG_DOUBLE && __HAVE_DISTINCT_FLOAT128
+  NARROW_ADD_ROUND_TO_ODD (x, y, _Float64x, union ieee854_long_double, l,
+			   mantissa3);
+#else
+  NARROW_ADD_TRIVIAL (x, y, _Float64x);
+#endif
+}
+libm_alias_float64x_float128 (add)
diff --git a/sysdeps/ieee754/ldbl-128/s_faddl.c b/sysdeps/ieee754/ldbl-128/s_faddl.c
new file mode 100644
index 0000000000..edbaa2103b
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128/s_faddl.c
@@ -0,0 +1,33 @@
+/* Add long double (ldbl-128) values, narrowing the result to float.
+   Copyright (C) 2018 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/>.  */
+
+#define f32addf64x __hide_f32addf64x
+#define f32addf128 __hide_f32addf128
+#include <math.h>
+#undef f32addf64x
+#undef f32addf128
+
+#include <math-narrow.h>
+
+float
+__faddl (_Float128 x, _Float128 y)
+{
+  NARROW_ADD_ROUND_TO_ODD (x, y, float, union ieee854_long_double, l,
+			   mantissa3);
+}
+libm_alias_float_ldouble (add)
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_daddl.c b/sysdeps/ieee754/ldbl-128ibm/s_daddl.c
new file mode 100644
index 0000000000..28b7e06ace
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128ibm/s_daddl.c
@@ -0,0 +1,27 @@
+/* Add long double (ldbl-128ibm) values, narrowing the result to double.
+   Copyright (C) 2018 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/>.  */
+
+#include <math.h>
+#include <math-narrow.h>
+
+double
+__daddl (long double x, long double y)
+{
+  NARROW_ADD_TRIVIAL (x, y, double);
+}
+libm_alias_double_ldouble (add)
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_faddl.c b/sysdeps/ieee754/ldbl-128ibm/s_faddl.c
new file mode 100644
index 0000000000..55a391885c
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128ibm/s_faddl.c
@@ -0,0 +1,27 @@
+/* Add long double (ldbl-128ibm) values, narrowing the result to float.
+   Copyright (C) 2018 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/>.  */
+
+#include <math.h>
+#include <math-narrow.h>
+
+float
+__faddl (long double x, long double y)
+{
+  NARROW_ADD_TRIVIAL (x, y, float);
+}
+libm_alias_float_ldouble (add)
diff --git a/sysdeps/ieee754/ldbl-96/s_daddl.c b/sysdeps/ieee754/ldbl-96/s_daddl.c
new file mode 100644
index 0000000000..d1e3c17bc7
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-96/s_daddl.c
@@ -0,0 +1,33 @@
+/* Add long double (ldbl-96) values, narrowing the result to double.
+   Copyright (C) 2018 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/>.  */
+
+#define f32xaddf64x __hide_f32xaddf64x
+#define f64addf64x __hide_f64addf64x
+#include <math.h>
+#undef f32xaddf64x
+#undef f64addf64x
+
+#include <math-narrow.h>
+
+double
+__daddl (long double x, long double y)
+{
+  NARROW_ADD_ROUND_TO_ODD (x, y, double, union ieee854_long_double, l,
+			   mantissa1);
+}
+libm_alias_double_ldouble (add)
diff --git a/sysdeps/ieee754/ldbl-96/s_faddl.c b/sysdeps/ieee754/ldbl-96/s_faddl.c
new file mode 100644
index 0000000000..4164774cd4
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-96/s_faddl.c
@@ -0,0 +1,31 @@
+/* Add long double (ldbl-96) values, narrowing the result to float.
+   Copyright (C) 2018 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/>.  */
+
+#define f32addf64x __hide_f32addf64x
+#include <math.h>
+#undef f32addf64x
+
+#include <math-narrow.h>
+
+float
+__faddl (long double x, long double y)
+{
+  NARROW_ADD_ROUND_TO_ODD (x, y, float, union ieee854_long_double, l,
+			   mantissa1);
+}
+libm_alias_float_ldouble (add)
diff --git a/sysdeps/ieee754/ldbl-opt/Makefile b/sysdeps/ieee754/ldbl-opt/Makefile
index 38afe38ab8..2340e4ce29 100644
--- a/sysdeps/ieee754/ldbl-opt/Makefile
+++ b/sysdeps/ieee754/ldbl-opt/Makefile
@@ -44,7 +44,7 @@ libnldbl-calls = asprintf dprintf fprintf fscanf fwprintf fwscanf iovfscanf \
 		 isoc99_vwscanf isoc99_vfwscanf isoc99_vswscanf \
 		 nextup nextdown totalorder totalordermag getpayload \
 		 canonicalize setpayload setpayloadsig llogb fmaxmag fminmag \
-		 roundeven fromfp ufromfp fromfpx ufromfpx
+		 roundeven fromfp ufromfp fromfpx ufromfpx fadd dadd
 libnldbl-routines = $(libnldbl-calls:%=nldbl-%)
 libnldbl-inhibit-o = $(object-suffixes)
 libnldbl-static-only-routines = $(libnldbl-routines)
@@ -86,6 +86,7 @@ CFLAGS-nldbl-csinh.c = -fno-builtin-csinhl
 CFLAGS-nldbl-csqrt.c = -fno-builtin-csqrtl
 CFLAGS-nldbl-ctan.c = -fno-builtin-ctanl
 CFLAGS-nldbl-ctanh.c = -fno-builtin-ctanhl
+CFLAGS-nldbl-dadd.c = -fno-builtin-daddl
 CFLAGS-nldbl-erf.c = -fno-builtin-erfl
 CFLAGS-nldbl-erfc.c = -fno-builtin-erfcl
 CFLAGS-nldbl-exp.c = -fno-builtin-expl
@@ -93,6 +94,7 @@ CFLAGS-nldbl-exp10.c = -fno-builtin-exp10l
 CFLAGS-nldbl-exp2.c = -fno-builtin-exp2l
 CFLAGS-nldbl-expm1.c = -fno-builtin-expm1l
 CFLAGS-nldbl-fabs.c = -fno-builtin-fabsl
+CFLAGS-nldbl-fadd.c = -fno-builtin-faddl
 CFLAGS-nldbl-fdim.c = -fno-builtin-fdiml
 CFLAGS-nldbl-finite.c = -fno-builtin-finitel
 CFLAGS-nldbl-floor.c = -fno-builtin-floorl
diff --git a/sysdeps/ieee754/ldbl-opt/Versions b/sysdeps/ieee754/ldbl-opt/Versions
index d3f0beaef2..e50efa3520 100644
--- a/sysdeps/ieee754/ldbl-opt/Versions
+++ b/sysdeps/ieee754/ldbl-opt/Versions
@@ -97,4 +97,10 @@ libm {
     sincosl; tanl; tanhl; truncl; expl; __finitel; __signbitl;
     __fpclassifyl; nexttowardf; nexttoward; __nldbl_nexttowardf;
   }
+  GLIBC_2.28 {
+    # Functions taking long double = double argument and rounding
+    # result to double (same as f32x*f64 functions, but those names
+    # are not reserved in TS 18661-1).
+    __nldbl_daddl;
+  }
 }
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-compat.h b/sysdeps/ieee754/ldbl-opt/nldbl-compat.h
index d61fbb2f64..74f0e459fa 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-compat.h
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-compat.h
@@ -101,5 +101,8 @@ extern int __nldbl___obstack_vprintf_chk (struct obstack *, int, const char *,
 					  __gnuc_va_list) __THROW;
 extern void __nldbl___vsyslog_chk (int, int, const char *, va_list);
 
+/* The original declarations of these were hidden by the including
+   file.  */
+extern double __nldbl_daddl (double, double) __THROW;
 
 #endif /* __NLDBL_COMPAT_H */
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-dadd.c b/sysdeps/ieee754/ldbl-opt/nldbl-dadd.c
new file mode 100644
index 0000000000..acbcb3ff75
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-dadd.c
@@ -0,0 +1,28 @@
+/* Compatibility routine for IEEE double as long double for dadd.
+   Copyright (C) 2018 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/>.  */
+
+#define daddl __hide_daddl
+#include "nldbl-compat.h"
+#undef daddl
+
+double
+attribute_hidden
+daddl (double x, double y)
+{
+  return __nldbl_daddl (x, y);
+}
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-fadd.c b/sysdeps/ieee754/ldbl-opt/nldbl-fadd.c
new file mode 100644
index 0000000000..c31a6db475
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-fadd.c
@@ -0,0 +1,28 @@
+/* Compatibility routine for IEEE double as long double for fadd.
+   Copyright (C) 2018 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/>.  */
+
+#define faddl __hide_faddl
+#include "nldbl-compat.h"
+#undef faddl
+
+float
+attribute_hidden
+faddl (double x, double y)
+{
+  return fadd (x, y);
+}
diff --git a/sysdeps/ieee754/soft-fp/s_daddl.c b/sysdeps/ieee754/soft-fp/s_daddl.c
new file mode 100644
index 0000000000..efe3772413
--- /dev/null
+++ b/sysdeps/ieee754/soft-fp/s_daddl.c
@@ -0,0 +1,59 @@
+/* Add long double (ldbl-128) values, narrowing the result to double,
+   using soft-fp.
+   Copyright (C) 2018 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/>.  */
+
+#define f32xaddf64x __hide_f32xaddf64x
+#define f32xaddf128 __hide_f32xaddf128
+#define f64addf64x __hide_f64addf64x
+#define f64addf128 __hide_f64addf128
+#include <math.h>
+#undef f32xaddf64x
+#undef f32xaddf128
+#undef f64addf64x
+#undef f64addf128
+
+#include <math-narrow.h>
+#include <soft-fp.h>
+#include <double.h>
+#include <quad.h>
+
+double
+__daddl (_Float128 x, _Float128 y)
+{
+  FP_DECL_EX;
+  FP_DECL_Q (X);
+  FP_DECL_Q (Y);
+  FP_DECL_Q (R);
+  FP_DECL_D (RN);
+  double ret;
+
+  FP_INIT_ROUNDMODE;
+  FP_UNPACK_SEMIRAW_Q (X, x);
+  FP_UNPACK_SEMIRAW_Q (Y, y);
+  FP_ADD_Q (R, X, Y);
+#if (2 * _FP_W_TYPE_SIZE) < _FP_FRACBITS_Q
+  FP_TRUNC (D, Q, 2, 4, RN, R);
+#else
+  FP_TRUNC (D, Q, 1, 2, RN, R);
+#endif
+  FP_PACK_SEMIRAW_D (ret, RN);
+  FP_HANDLE_EXCEPTIONS;
+  CHECK_NARROW_ADD (ret, x, y);
+  return ret;
+}
+libm_alias_double_ldouble (add)
diff --git a/sysdeps/ieee754/soft-fp/s_fadd.c b/sysdeps/ieee754/soft-fp/s_fadd.c
new file mode 100644
index 0000000000..606e527300
--- /dev/null
+++ b/sysdeps/ieee754/soft-fp/s_fadd.c
@@ -0,0 +1,56 @@
+/* Add double values, narrowing the result to float, using soft-fp.
+   Copyright (C) 2018 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/>.  */
+
+#define f32addf64 __hide_f32addf64
+#define f32addf32x __hide_f32addf32x
+#define faddl __hide_faddl
+#include <math.h>
+#undef f32addf64
+#undef f32addf32x
+#undef faddl
+
+#include <math-narrow.h>
+#include <soft-fp.h>
+#include <single.h>
+#include <double.h>
+
+float
+__fadd (double x, double y)
+{
+  FP_DECL_EX;
+  FP_DECL_D (X);
+  FP_DECL_D (Y);
+  FP_DECL_D (R);
+  FP_DECL_S (RN);
+  float ret;
+
+  FP_INIT_ROUNDMODE;
+  FP_UNPACK_SEMIRAW_D (X, x);
+  FP_UNPACK_SEMIRAW_D (Y, y);
+  FP_ADD_D (R, X, Y);
+#if _FP_W_TYPE_SIZE < _FP_FRACBITS_D
+  FP_TRUNC (S, D, 1, 2, RN, R);
+#else
+  FP_TRUNC (S, D, 1, 1, RN, R);
+#endif
+  FP_PACK_SEMIRAW_S (ret, RN);
+  FP_HANDLE_EXCEPTIONS;
+  CHECK_NARROW_ADD (ret, x, y);
+  return ret;
+}
+libm_alias_float_double (add)
diff --git a/sysdeps/ieee754/soft-fp/s_faddl.c b/sysdeps/ieee754/soft-fp/s_faddl.c
new file mode 100644
index 0000000000..42c4422060
--- /dev/null
+++ b/sysdeps/ieee754/soft-fp/s_faddl.c
@@ -0,0 +1,55 @@
+/* Add long double (ldbl-128) values, narrowing the result to float,
+   using soft-fp.
+   Copyright (C) 2018 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/>.  */
+
+#define f32addf64x __hide_f32addf64x
+#define f32addf128 __hide_f32addf128
+#include <math.h>
+#undef f32addf64x
+#undef f32addf128
+
+#include <math-narrow.h>
+#include <soft-fp.h>
+#include <single.h>
+#include <quad.h>
+
+float
+__faddl (_Float128 x, _Float128 y)
+{
+  FP_DECL_EX;
+  FP_DECL_Q (X);
+  FP_DECL_Q (Y);
+  FP_DECL_Q (R);
+  FP_DECL_S (RN);
+  float ret;
+
+  FP_INIT_ROUNDMODE;
+  FP_UNPACK_SEMIRAW_Q (X, x);
+  FP_UNPACK_SEMIRAW_Q (Y, y);
+  FP_ADD_Q (R, X, Y);
+#if (2 * _FP_W_TYPE_SIZE) < _FP_FRACBITS_Q
+  FP_TRUNC (S, Q, 1, 4, RN, R);
+#else
+  FP_TRUNC (S, Q, 1, 2, RN, R);
+#endif
+  FP_PACK_SEMIRAW_S (ret, RN);
+  FP_HANDLE_EXCEPTIONS;
+  CHECK_NARROW_ADD (ret, x, y);
+  return ret;
+}
+libm_alias_float_ldouble (add)