Fortran: Use _Float128 rather than __float128 for c_float128 kind.

The GNU Fortran manual documents that the c_float128 kind corresponds
to __float128, but in fact the implementation uses float128_type_node,
which is _Float128.  Both refer to the 128-bit IEEE/ISO encoding, but
some targets including aarch64 only define _Float128 and not __float128,
and do not provide quadmath.h.  This caused errors in some test cases
referring to __float128.

This patch changes the documentation (including code comments) and
test cases to use _Float128 to match the implementation.

2021-09-16  Sandra Loosemore  <sandra@codesourcery.com>

gcc/fortran/

	* intrinsic.texi (ISO_C_BINDING): Change C_FLOAT128 to correspond
	to _Float128 rather than __float128.
	* iso-c-binding.def (c_float128): Update comments.
	* trans-intrinsic.c (gfc_builtin_decl_for_float_kind): Likewise.
	(build_round_expr): Likewise.
	(gfc_build_intrinsic_lib_fndcecls): Likewise.
	* trans-types.h (gfc_real16_is_float128): Likewise.

gcc/testsuite/
	* gfortran.dg/PR100914.c: Do not include quadmath.h.  Use
	_Float128 _Complex instead of __complex128.
	* gfortran.dg/PR100914.f90: Add -Wno-pedantic to suppress error
	about use of _Float128.
	* gfortran.dg/c-interop/typecodes-array-float128-c.c: Use
	_Float128 instead of __float128.
	* gfortran.dg/c-interop/typecodes-sanity-c.c: Likewise.
	* gfortran.dg/c-interop/typecodes-scalar-float128-c.c: Likewise.
	* lib/target-supports.exp
	(check_effective_target_fortran_real_c_float128): Update comments.

libgfortran/
	* ISO_Fortran_binding.h: Update comments.
	* runtime/ISO_Fortran_binding.c: Likewise.

4 files changed, 9 insertions, 9 deletions

diff --git a/gcc/fortran/intrinsic.texi b/gcc/fortran/intrinsic.texi
index 1aacd33..1b9a89d 100644
--- a/gcc/fortran/intrinsic.texi
+++ b/gcc/fortran/intrinsic.texi
@@ -15193,8 +15193,8 @@ In addition to the integer named constants required by the Fortran 2003
 standard and @code{C_PTRDIFF_T} of TS 29113, GNU Fortran provides as an
 extension named constants for the 128-bit integer types supported by the
 C compiler: @code{C_INT128_T, C_INT_LEAST128_T, C_INT_FAST128_T}.
-Furthermore, if @code{__float128} is supported in C, the named constants
-@code{C_FLOAT128, C_FLOAT128_COMPLEX} are defined.
+Furthermore, if @code{_Float128} is supported in C, the named constants
+@code{C_FLOAT128} and @code{C_FLOAT128_COMPLEX} are defined.
 
 @multitable @columnfractions .15 .35 .35 .35
 @headitem Fortran Type  @tab Named constant         @tab C type                                @tab Extension
@@ -15225,11 +15225,11 @@ Furthermore, if @code{__float128} is supported in C, the named constants
 @item @code{REAL}   @tab @code{C_FLOAT}         @tab @code{float}
 @item @code{REAL}   @tab @code{C_DOUBLE}        @tab @code{double}
 @item @code{REAL}   @tab @code{C_LONG_DOUBLE}   @tab @code{long double}
-@item @code{REAL}   @tab @code{C_FLOAT128}      @tab @code{__float128}                    @tab Ext.
+@item @code{REAL}   @tab @code{C_FLOAT128}      @tab @code{_Float128}                    @tab Ext.
 @item @code{COMPLEX}@tab @code{C_FLOAT_COMPLEX} @tab @code{float _Complex}
 @item @code{COMPLEX}@tab @code{C_DOUBLE_COMPLEX}@tab @code{double _Complex}
 @item @code{COMPLEX}@tab @code{C_LONG_DOUBLE_COMPLEX}@tab @code{long double _Complex}
-@item @code{REAL}   @tab @code{C_FLOAT128_COMPLEX}   @tab @code{__float128 _Complex}      @tab Ext.
+@item @code{COMPLEX}@tab @code{C_FLOAT128_COMPLEX}   @tab @code{_Float128 _Complex}      @tab Ext.
 @item @code{LOGICAL}@tab @code{C_BOOL}          @tab @code{_Bool}
 @item @code{CHARACTER}@tab @code{C_CHAR}        @tab @code{char}
 @end multitable
diff --git a/gcc/fortran/iso-c-binding.def b/gcc/fortran/iso-c-binding.def
index e65c750..50256fe 100644
--- a/gcc/fortran/iso-c-binding.def
+++ b/gcc/fortran/iso-c-binding.def
@@ -116,7 +116,7 @@ NAMED_REALCST (ISOCBINDING_LONG_DOUBLE, "c_long_double", \
                get_real_kind_from_node (long_double_type_node), GFC_STD_F2003)
 
 /* GNU Extension.  Note that the equivalence here is specifically to
-   the IEEE 128-bit type __float128; if that does not map onto a type
+   the IEEE 128-bit type _Float128; if that does not map onto a type
    otherwise supported by the Fortran front end, get_real_kind_from_node
    will reject it as unsupported.  */
 NAMED_REALCST (ISOCBINDING_FLOAT128, "c_float128", \
diff --git a/gcc/fortran/trans-intrinsic.c b/gcc/fortran/trans-intrinsic.c
index 46670ba..42a995b 100644
--- a/gcc/fortran/trans-intrinsic.c
+++ b/gcc/fortran/trans-intrinsic.c
@@ -175,7 +175,7 @@ gfc_builtin_decl_for_float_kind (enum built_in_function double_built_in,
 
   if (gfc_real_kinds[i].c_float128)
     {
-      /* For __float128, the story is a bit different, because we return
+      /* For _Float128, the story is a bit different, because we return
 	 a decl to a library function rather than a built-in.  */
       gfc_intrinsic_map_t *m;
       for (m = gfc_intrinsic_map; m->double_built_in != double_built_in ; m++)
@@ -387,7 +387,7 @@ build_round_expr (tree arg, tree restype)
   resprec = TYPE_PRECISION (restype);
 
   /* Depending on the type of the result, choose the int intrinsic (iround,
-     available only as a builtin, therefore cannot use it for __float128), long
+     available only as a builtin, therefore cannot use it for _Float128), long
      int intrinsic (lround family) or long long intrinsic (llround).  If we
      don't have an appropriate function that converts directly to the integer
      type (such as kind == 16), just use ROUND, and then convert the result to
@@ -689,7 +689,7 @@ gfc_build_intrinsic_lib_fndecls (void)
   if (gfc_real16_is_float128)
   {
     /* If we have soft-float types, we create the decls for their
-       C99-like library functions.  For now, we only handle __float128
+       C99-like library functions.  For now, we only handle _Float128
        q-suffixed functions.  */
 
     tree type, complex_type, func_1, func_2, func_cabs, func_frexp;
diff --git a/gcc/fortran/trans-types.h b/gcc/fortran/trans-types.h
index 3b45ce2..6804bfe 100644
--- a/gcc/fortran/trans-types.h
+++ b/gcc/fortran/trans-types.h
@@ -55,7 +55,7 @@ extern GTY(()) tree gfc_charlen_type_node;
 
 /* The following flags give us information on the correspondence of
    real (and complex) kinds with C floating-point types long double
-   and __float128.  */
+   and _Float128.  */
 extern bool gfc_real16_is_float128;
 
 enum gfc_packed {