On 8/10/21 2:29 AM, Tobias Burnus wrote:
[snip]
To conclude: I like the code changes (LGTM); the
'__float128' -> 'TFmode' comment change also matches the code.
However, I think both longer comments need to be updated.
OK. I used your wording verbatim for the first one. For the second
one, I'm still pretty confused as I think it is at least theoretically
possible on PowerPC to have a target with 64-bit long double (AIX?) that
also supports the __ibm128 format, and it would be wrong to assume that
*any* 128-bit mode that's not long double is IEEE. So I decided the
best thing is just to replace the FIXME with a pointer to the issue I
opened yesterday
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101835
and folks who actually understand this stuff can add some more
discussion there.
Here's a new version of the patch with changes to the two comments only.
OK to commit this one?
-Sandra
commit e496723ec6ee0fcf5b0c58920c74b1c9afa831de
Author: Sandra Loosemore <san...@codesourcery.com>
Date: Tue Aug 3 16:21:16 2021 -0700
Fix c_float128 and c_float128_complex definitions.
gfc_float128_type_node is only non-NULL on targets that support a
128-bit type that is not long double. Use float128_type_node instead
when computing the value of the kind constants c_float128 and
c_float128_complex from the ISO_C_BINDING intrinsic module; this also
ensures it actually corresponds to __float128 (the IEEE encoding) and
not some other 128-bit floating-point type.
2021-08-10 Sandra Loosemore <san...@codesourcery.com>
gcc/fortran/
* iso-c-binding.def (c_float128, c_float128_complex): Check
float128_type_node instead of gfc_float128_type_node.
* trans-types.c (gfc_init_kinds, gfc_build_real_type):
Update comments re supported 128-bit floating-point types.
diff --git a/gcc/fortran/iso-c-binding.def b/gcc/fortran/iso-c-binding.def
index 8bf69ef..e65c750 100644
--- a/gcc/fortran/iso-c-binding.def
+++ b/gcc/fortran/iso-c-binding.def
@@ -114,9 +114,14 @@ NAMED_REALCST (ISOCBINDING_DOUBLE, "c_double", \
get_real_kind_from_node (double_type_node), GFC_STD_F2003)
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
+ otherwise supported by the Fortran front end, get_real_kind_from_node
+ will reject it as unsupported. */
NAMED_REALCST (ISOCBINDING_FLOAT128, "c_float128", \
- gfc_float128_type_node == NULL_TREE \
- ? -4 : get_real_kind_from_node (gfc_float128_type_node), \
+ (float128_type_node == NULL_TREE \
+ ? -4 : get_real_kind_from_node (float128_type_node)), \
GFC_STD_GNU)
NAMED_CMPXCST (ISOCBINDING_FLOAT_COMPLEX, "c_float_complex", \
get_real_kind_from_node (float_type_node), GFC_STD_F2003)
@@ -124,9 +129,11 @@ NAMED_CMPXCST (ISOCBINDING_DOUBLE_COMPLEX, "c_double_complex", \
get_real_kind_from_node (double_type_node), GFC_STD_F2003)
NAMED_CMPXCST (ISOCBINDING_LONG_DOUBLE_COMPLEX, "c_long_double_complex", \
get_real_kind_from_node (long_double_type_node), GFC_STD_F2003)
+
+/* GNU Extension. Similar issues to c_float128 above. */
NAMED_CMPXCST (ISOCBINDING_FLOAT128_COMPLEX, "c_float128_complex", \
- gfc_float128_type_node == NULL_TREE \
- ? -4 : get_real_kind_from_node (gfc_float128_type_node), \
+ (float128_type_node == NULL_TREE \
+ ? -4 : get_real_kind_from_node (float128_type_node)), \
GFC_STD_GNU)
NAMED_LOGCST (ISOCBINDING_BOOL, "c_bool", \
diff --git a/gcc/fortran/trans-types.c b/gcc/fortran/trans-types.c
index 50fda43..26dbbd8 100644
--- a/gcc/fortran/trans-types.c
+++ b/gcc/fortran/trans-types.c
@@ -446,7 +446,7 @@ gfc_init_kinds (void)
if (!targetm.scalar_mode_supported_p (mode))
continue;
- /* Only let float, double, long double and __float128 go through.
+ /* Only let float, double, long double and TFmode go through.
Runtime support for others is not provided, so they would be
useless. */
if (!targetm.libgcc_floating_mode_supported_p (mode))
@@ -471,7 +471,14 @@ gfc_init_kinds (void)
We round up so as to handle IA-64 __floatreg (RFmode), which is an
82 bit type. Not to be confused with __float80 (XFmode), which is
an 80 bit type also supported by IA-64. So XFmode should come out
- to be kind=10, and RFmode should come out to be kind=11. Egads. */
+ to be kind=10, and RFmode should come out to be kind=11. Egads.
+
+ TODO: The kind calculation has to be modified to support all
+ three 128-bit floating-point modes on PowerPC as IFmode, KFmode,
+ and TFmode since the following line would all map to kind=16.
+ However, currently only float, double, long double, and TFmode
+ reach this code.
+ */
kind = (GET_MODE_PRECISION (mode) + 7) / 8;
@@ -851,6 +858,7 @@ gfc_build_real_type (gfc_real_info *info)
info->c_long_double = 1;
if (mode_precision != LONG_DOUBLE_TYPE_SIZE && mode_precision == 128)
{
+ /* See PR101835. */
info->c_float128 = 1;
gfc_real16_is_float128 = true;
}
