[Bug fortran/45424] [F08] Add IS_CONTIGUOUS intrinsic

[anlauf at gmx dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=45424

--- Comment #5 from Harald Anlauf <anlauf at gmx dot de> ---
Looking at the F2k18 draft, I see some updates and clarifications:

16.9.105 IS_CONTIGUOUS (ARRAY)
Description. Array contiguity test (8.5.7).
Class. Inquiry function.
Argument. ARRAY may be of any type. It shall be assumed-rank or an array. If it
is a pointer it shall be associated.
Result Characteristics. Default logical scalar.
Result Value. The result has the value true if ARRAY has rank zero or is
contiguous, and false otherwise.

[Example elided]

The clarification about rank zero is certainly helpful.

Furthermore:

8.5.7 CONTIGUOUS attribute

NOTE 1
If a derived type has only one component that is not zero-sized, it is
processor dependent whether a structure component of a contiguous array
of that type is contiguous. That is, the derived type might contain padding
on some processors.

This gives some freedom for a "conservative" implementation of the
intrinsic.