cartesian: dace backends missing support for casting in variable k offsets

[romanc]

Description

DaCe backends are currently missing support for casting in VariableKOffset. The issue comes from the fact that we "sympify" index computations in the _visit_offsets() function of tasklet_codegen.

gt4py/src/gt4py/cartesian/gtc/dace/expansion/tasklet_codegen.py

Lines 46 to 49 in 1a46fb0

	sym_offsets = [
	dace.symbolic.pystr_to_symbolic(self.visit(off, **kwargs))
	for off in (node.to_dict()["i"], node.to_dict()["j"], node.k)
	]

However, before we "sympify", casts are already translated to dace types, e.g. dace.int64 and then this isn't plain python anymore and fails sympy's python parser.

PR ... puts a mitigation in place to catch casts in indices of type VariableKOffset in the DaCe backends. The PR also adds a codgen test which

• uses xfail for all DaCe backends
• succeeds for all other backends

That behavior can be simplified once DaCe backends also support casting in variable k offset expressions.

[romanc]

@FlorianDeconinck we should make sure this work out of the box in the oir to stree bridge. There's no reason to keep this limitation now that build from scratch. We can just enable the tests on our feature branch and make sure they pass

[FlorianDeconinck]

Yes:

https://github.com/romanc/gt4py/blob/fe66b5aa43be3fb7b555d392426f9f2a50af68a9/src/gt4py/cartesian/gtc/dace/oir_to_treeir.py#L313-L316