Hi all,
attached is a (technically) simple patch that implements the compiler
flag "-fdefault-real-16" for gfortran.
I know that there is some opposition against this, but I am proposing
it anyway, because I do think it is useful after all. My reasoning is
as follows:
1) Despite tons of -freal-X-real-Y flags, there currently is no way to
only promote the default real kind to real(16).
2) Since a variable of default REAL kind does not specify a KIND value
explicitly, it is quite natural for a compiler to control this by
means of flags.
3) gfortran already has -fdefault-real-8 (which is used in lots of
real-world codes AFAIK) and does support quad-precision variables.
4) Other compilers do have flags for this as well (e.g. ifort's
"-real-size 128" etc).
5) I know that it is possible, any maybe cleaner, to declare variables
with explicit kinds instead of relying on compiler flags, but for
large and historically grown codes it is not always straightforward to
do this right away.
6) The patch does not modify the default behavior of gfortran.
7) No one who dislikes such compiler flags is forced to use them.
8) I don't see how this flag can cause any harm. It adds additional
possibilities of using the compiler and thus makes gfortran more
powerful (and more compatible with other compilers).
The patch regtests cleanly on x86_64-linux-gnu. Ok for trunk?
Cheers,
Janus
2017-09-17 Janus Weil <ja...@gcc.gnu.org>
PR fortran/82143
* lang.opt: Add the option -fdefault-real-16.
* invoke.texi: Add documentation for -fdefault-real-16.
* trans-types.c (gfc_init_kinds): Implement -fdefault-real-16.
2017-09-17 Janus Weil <ja...@gcc.gnu.org>
PR fortran/82143
* gfortran.dg/promotion_3.f90: New test case.
Index: gcc/fortran/invoke.texi
===================================================================
--- gcc/fortran/invoke.texi (revision 252892)
+++ gcc/fortran/invoke.texi (working copy)
@@ -120,7 +120,7 @@ by type. Explanations are in the following sectio
-fd-lines-as-comments @gol
-fdec -fdec-structure -fdec-intrinsic-ints -fdec-static -fdec-math @gol
-fdefault-double-8 -fdefault-integer-8 @gol
--fdefault-real-8 -fdollar-ok -ffixed-line-length-@var{n} @gol
+-fdefault-real-8 -fdefault-real-16 -fdollar-ok -ffixed-line-length-@var{n} @gol
-ffixed-line-length-none -ffree-form -ffree-line-length-@var{n} @gol
-ffree-line-length-none -fimplicit-none -finteger-4-integer-8 @gol
-fmax-identifier-length -fmodule-private -ffixed-form -fno-range-check @gol
@@ -404,6 +404,14 @@ the default width of @code{DOUBLE PRECISION} to 16
@code{-fdefault-double-8} is given, too. Unlike @option{-freal-4-real-8},
it does not promote variables with explicit kind declaration.
+@item -fdefault-real-16
+@opindex @code{fdefault-real-16}
+Set the default real type to a 16 byte wide type. This option also affects
+the kind of non-double real constants like @code{1.0}, and does promote
+the default width of @code{DOUBLE PRECISION} to 16 bytes if possible, unless
+@code{-fdefault-double-8} is given. Unlike @option{-freal-4-real-16},
+it does not promote variables with explicit kind declaration.
+
@item -fdefault-double-8
@opindex @code{fdefault-double-8}
Set the @code{DOUBLE PRECISION} type to an 8 byte wide type. Do nothing if
this
Index: gcc/fortran/lang.opt
===================================================================
--- gcc/fortran/lang.opt (revision 252892)
+++ gcc/fortran/lang.opt (working copy)
@@ -460,6 +460,10 @@ fdefault-real-8
Fortran Var(flag_default_real)
Set the default real kind to an 8 byte wide type.
+fdefault-real-16
+Fortran Var(flag_default_real_16)
+Set the default real kind to an 16 byte wide type.
+
fdollar-ok
Fortran Var(flag_dollar_ok)
Allow dollar signs in entity names.
Index: gcc/fortran/trans-types.c
===================================================================
--- gcc/fortran/trans-types.c (revision 252892)
+++ gcc/fortran/trans-types.c (working copy)
@@ -538,6 +538,14 @@ gfc_init_kinds (void)
gfc_default_real_kind = 8;
}
+ else if (flag_default_real_16)
+ {
+ if (!saw_r16)
+ gfc_fatal_error ("REAL(KIND=16) is not available for "
+ "%<-fdefault-real-16%> option");
+
+ gfc_default_real_kind = 16;
+ }
else if (flag_real4_kind == 8)
{
if (!saw_r8)
@@ -577,7 +585,7 @@ gfc_init_kinds (void)
if (flag_default_real && flag_default_double && saw_r8)
gfc_default_double_kind = 8;
- else if (flag_default_real && saw_r16)
+ else if ((flag_default_real || flag_default_real_16) && saw_r16)
gfc_default_double_kind = 16;
else if (flag_real8_kind == 4)
{
! { dg-do run }
! { dg-options "-fdefault-real-16" }
!
! PR 82143: add a -fdefault-real-16 flag
!
! Contributed by Janus Weil <ja...@gcc.gnu.org>
real :: r
real(kind=4) :: r4
real(kind=8) :: r8
double precision :: d
print *, kind(r4), kind(r8), kind(r), kind(d)
if (kind(r4) /= 4) call abort
if (kind(r8) /= 8) call abort
if (kind(r) /= 16) call abort
if (kind(d) /= 16) call abort
end
