Add narrowing square root functions

This patch adds the narrowing square root functions from TS 18661-1 /
TS 18661-3 / C2X to glibc's libm: fsqrt, fsqrtl, dsqrtl, f32sqrtf64,
f32sqrtf32x, f32xsqrtf64 for all configurations; f32sqrtf64x,
f32sqrtf128, f64sqrtf64x, f64sqrtf128, f32xsqrtf64x, f32xsqrtf128,
f64xsqrtf128 for configurations with _Float64x and _Float128;
__f32sqrtieee128 and __f64sqrtieee128 aliases in the powerpc64le case
(for calls to fsqrtl and dsqrtl when long double is IEEE binary128).
Corresponding tgmath.h macro support is also added.

The changes are mostly similar to those for the other narrowing
functions previously added, so the description of those generally
applies to this patch as well.  However, the not-actually-narrowing
cases (where the two types involved in the function have the same
floating-point format) are aliased to sqrt, sqrtl or sqrtf128 rather
than needing a separately built not-actually-narrowing function such
as was needed for add / sub / mul / div.  Thus, there is no
__nldbl_dsqrtl name for ldbl-opt because no such name was needed
(whereas the other functions needed such a name since the only other
name for that entry point was e.g. f32xaddf64, not reserved by TS
18661-1); the headers are made to arrange for sqrt to be called in
that case instead.

The DIAG_* calls in sysdeps/ieee754/soft-fp/s_dsqrtl.c are because
they were observed to be needed in GCC 7 testing of
riscv32-linux-gnu-rv32imac-ilp32.  The other sysdeps/ieee754/soft-fp/
files added didn't need such DIAG_* in any configuration I tested with
build-many-glibcs.py, but if they do turn out to be needed in more
files with some other configuration / GCC version, they can always be
added there.

I reused the same test inputs in auto-libm-test-in as for
non-narrowing sqrt rather than adding extra or separate inputs for
narrowing sqrt.  The tests in libm-test-narrow-sqrt.inc also follow
those for non-narrowing sqrt.

Tested as followed: natively with the full glibc testsuite for x86_64
(GCC 11, 7, 6) and x86 (GCC 11); with build-many-glibcs.py with GCC
11, 7 and 6; cross testing of math/ tests for powerpc64le, powerpc32
hard float, mips64 (all three ABIs, both hard and soft float).  The
different GCC versions are to cover the different cases in tgmath.h
and tgmath.h tests properly (GCC 6 has _Float* only as typedefs in
glibc headers, GCC 7 has proper _Float* support, GCC 8 adds
__builtin_tgmath).

4 files changed, 23 insertions, 0 deletions

diff --git a/sysdeps/ieee754/float128/float128_private.h b/sysdeps/ieee754/float128/float128_private.h
index b6b6d3d5fd..13d1d63baf 100644
--- a/sysdeps/ieee754/float128/float128_private.h
+++ b/sysdeps/ieee754/float128/float128_private.h
@@ -138,6 +138,9 @@
 #define libm_alias_float_ldouble(func) libm_alias_float32_float128 (func)
 #undef libm_alias_double_ldouble
 #define libm_alias_double_ldouble(func) libm_alias_float64_float128 (func)
+#undef libm_alias_ldouble_narrow
+#define libm_alias_ldouble_narrow(from, to)	\
+  libm_alias_float128_narrow (from, to)
 
 #include <math-use-builtins.h>
 #undef USE_NEARBYINTL_BUILTIN
@@ -284,6 +287,8 @@
 #define __ddivl __f64divf128
 #define __fmull __f32mulf128
 #define __dmull __f64mulf128
+#define __fsqrtl __f32sqrtf128
+#define __dsqrtl __f64sqrtf128
 #define __fsubl __f32subf128
 #define __dsubl __f64subf128
 
diff --git a/sysdeps/ieee754/float128/s_f32sqrtf128.c b/sysdeps/ieee754/float128/s_f32sqrtf128.c
new file mode 100644
index 0000000000..74e91abd4d
--- /dev/null
+++ b/sysdeps/ieee754/float128/s_f32sqrtf128.c
@@ -0,0 +1,6 @@
+#define f32sqrtf64x __hide_f32sqrtf64x
+#define f32sqrtf128 __hide_f32sqrtf128
+#include <float128_private.h>
+#undef f32sqrtf64x
+#undef f32sqrtf128
+#include "../ldbl-128/s_fsqrtl.c"
diff --git a/sysdeps/ieee754/float128/s_f64sqrtf128.c b/sysdeps/ieee754/float128/s_f64sqrtf128.c
new file mode 100644
index 0000000000..8373879d42
--- /dev/null
+++ b/sysdeps/ieee754/float128/s_f64sqrtf128.c
@@ -0,0 +1,10 @@
+#define f32xsqrtf64x __hide_f32xsqrtf64x
+#define f32xsqrtf128 __hide_f32xsqrtf128
+#define f64sqrtf64x __hide_f64sqrtf64x
+#define f64sqrtf128 __hide_f64sqrtf128
+#include <float128_private.h>
+#undef f32xsqrtf64x
+#undef f32xsqrtf128
+#undef f64sqrtf64x
+#undef f64sqrtf128
+#include "../ldbl-128/s_dsqrtl.c"
diff --git a/sysdeps/ieee754/float128/s_f64xsqrtf128.c b/sysdeps/ieee754/float128/s_f64xsqrtf128.c
new file mode 100644
index 0000000000..383f92a94e
--- /dev/null
+++ b/sysdeps/ieee754/float128/s_f64xsqrtf128.c
@@ -0,0 +1,2 @@
+#include <float128_private.h>
+#include "../ldbl-128/s_f64xsqrtf128.c"