libgfortran: Fix up LIBGFOR_CHECK_FLOAT128 [PR106137]

My recent gfortran + libgfortran patch apparently broke (some?) aarch64
builds.  While it is desirable to use just _Float128 rather than __float128,
we only want to use it (and e.g. define HAVE_FLOAT128) on targets where
_Float128 is supported and long double isn't IEEE quad precision.
Which is targets that support __float128 type which we have been testing
for before - _Float128 is supported on those targets and on targets where
long double is IEEE quad precision.

So, the following patch restores check for whether __float128 is supported
into the LIBGFOR_CHECK_FLOAT128 check which determines whether
HAVE_FLOAT128 is defined or whether to use libquadmath, so that e.g. on
aarch64 where long double is IEEE quad we don't do that.

2022-06-29  Jakub Jelinek  <jakub@redhat.com>

	PR bootstrap/106137
	* acinclude.m4 (LIBGFOR_CHECK_FLOAT128): Adjust comment.
	Also test for __float128.
	(HAVE_FLOAT128): Adjust description.
	* config.h.in: Regenerated.
	* configure: Regenerated.

3 files changed, 24 insertions, 6 deletions

diff --git a/libgfortran/acinclude.m4 b/libgfortran/acinclude.m4
index dbf687e..7585df1 100644
--- a/libgfortran/acinclude.m4
+++ b/libgfortran/acinclude.m4
@@ -261,7 +261,7 @@ __mingw_snprintf (NULL, 0, "%d\n", 1);
   fi
 ])
 
-dnl Check whether we have a __float128 type
+dnl Check whether we have a __float128 and _Float128 type
 AC_DEFUN([LIBGFOR_CHECK_FLOAT128], [
   LIBQUADSPEC=
   LIBQUADLIB=
@@ -276,7 +276,6 @@ AC_DEFUN([LIBGFOR_CHECK_FLOAT128], [
    GCC_TRY_COMPILE_OR_LINK([
     _Float128 foo (_Float128 x)
     {
-
      _Complex _Float128 z1, z2;
 
      z1 = x;
@@ -290,11 +289,18 @@ AC_DEFUN([LIBGFOR_CHECK_FLOAT128], [
     {
       return x * __builtin_huge_valf128 ();
     }
+
+    __float128 baz (__float128 x)
+    {
+      return x * __builtin_huge_valf128 ();
+    }
   ],[
     foo (1.2F128);
     bar (1.2F128);
+    baz (1.2F128);
     foo (1.2Q);
     bar (1.2Q);
+    baz (1.2Q);
   ],[
     libgfor_cv_have_float128=yes
   ],[
@@ -310,7 +316,7 @@ AC_DEFUN([LIBGFOR_CHECK_FLOAT128], [
     if test "x$USE_IEC_60559" = xyes; then
       AC_DEFINE(USE_IEC_60559, 1, [Define if IEC 60559 *f128 APIs should be used for _Float128.])
     fi
-    AC_DEFINE(HAVE_FLOAT128, 1, [Define if have a usable _Float128 type.])
+    AC_DEFINE(HAVE_FLOAT128, 1, [Define if target has usable _Float128 and __float128 types.])
 
     dnl Check whether -Wl,--as-needed resp. -Wl,-zignore is supported
     dnl 
diff --git a/libgfortran/config.h.in b/libgfortran/config.h.in
index c403934..da2c44c 100644
--- a/libgfortran/config.h.in
+++ b/libgfortran/config.h.in
@@ -468,7 +468,7 @@
 /* Define to 1 if you have the <fenv.h> header file. */
 #undef HAVE_FENV_H
 
-/* Define if have a usable _Float128 type. */
+/* Define if target has usable _Float128 and __float128 types. */
 #undef HAVE_FLOAT128
 
 /* Define to 1 if you have the <floatingpoint.h> header file. */
diff --git a/libgfortran/configure b/libgfortran/configure
index c833591..c440721 100755
--- a/libgfortran/configure
+++ b/libgfortran/configure
@@ -30130,7 +30130,6 @@ else
 
     _Float128 foo (_Float128 x)
     {
-
      _Complex _Float128 z1, z2;
 
      z1 = x;
@@ -30145,14 +30144,21 @@ else
       return x * __builtin_huge_valf128 ();
     }
 
+    __float128 baz (__float128 x)
+    {
+      return x * __builtin_huge_valf128 ();
+    }
+
 int
 main ()
 {
 
     foo (1.2F128);
     bar (1.2F128);
+    baz (1.2F128);
     foo (1.2Q);
     bar (1.2Q);
+    baz (1.2Q);
 
   ;
   return 0;
@@ -30177,7 +30183,6 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 
     _Float128 foo (_Float128 x)
     {
-
      _Complex _Float128 z1, z2;
 
      z1 = x;
@@ -30192,14 +30197,21 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
       return x * __builtin_huge_valf128 ();
     }
 
+    __float128 baz (__float128 x)
+    {
+      return x * __builtin_huge_valf128 ();
+    }
+
 int
 main ()
 {
 
     foo (1.2F128);
     bar (1.2F128);
+    baz (1.2F128);
     foo (1.2Q);
     bar (1.2Q);
+    baz (1.2Q);
 
   ;
   return 0;