Thomas Koenig wrote:
below is a patch which improves dependency checking for array
assignments and calculation of string lengths.
Talking about dependencies, I wonder whether you would be interested
implementing the function
bool gfc_simply_noncontiguous (gfc_expr *);
or something similarly named.
It should return true, if the expression is known to be noncontiguous.
Such a function has many uses:
- Diagnostic to reject invalid code such as "contiguous_ptr =>
noncontiguous_target",* passing a noncontiguous expression to c_loc, and
possibly more
- Compile-time simplification for the IS_CONTIGUOUS intrinsic (not yet
implemented)
- If we pass a noncontiguous array to a contiguous dummy argument (i.e.
assumed-size, explicit-size or contiguous attribute), there is the check
if(new_array != old_array) { unpack(old_array,new_array);free(new_array)
}. If one knows that the array is noncontiguous, the
"if(new_array!=old_array) check could be removed (missed optimization)
- Potentially some more uses
Additionally, gfc_simply_noncontiguous has some bugs (both false
positive and false negative) - especially for BT_CLASS and for
ref-array/ref-substring handling (esp. when combined).
Actually, for
type t
integer i
end type t
type(t) :: foo(5)
is_contiguous(foo(:)%i), it depends on the aligning. (I think one needs
to call gfc_target_expr_size for "foo(:)" and compare it with the
storage size of foo(1)%i.) Of course, if there multiple components,
foo(:)%i is obviously noncontiguous. (For gfc_simply_contiguous, see the
Fortran standard for the exact definition of "simply contiguous", which
should be used with strict==true).
If you will work on it, please tell me - otherwise, I might start to
work on it. (It is not on top of my agenda, but for Fortran 2008's
IS_CONTIGUOUS() and for diagnostic reasons, I like to have it.)
* * *
But now, a bit belated, to your patch.
On 25.03.2013 16:43, Thomas Koenig wrote:
OK for trunk?
OK - except for the following three minor coding convention nits.
+}
+/* Return the difference between two expressions. Integer expressions of
Two empty lines before the comment.
+}
+
/* Returns 1 if the two ranges are the same and 0 if they are not (or if the
This time only one empty line is missing.
- mpz_clear (tmp);
+ mpz_clear (tmp); /* gfc_dep_difference returned true, so tmp was
initialized. */
I am not sure whether the comment is needed - but if you want to keep
it: The line is too long ;-)
Tobias
* Example for that
pointer, contiguous :: ptr
target :: tgt(5)
ptr => tgt(::2)
