Stride-based control

[SamirDroubi]

It is unclear to me whether stride-based control within procedure is not supported due to a bunch of bugs/over-conservative implementations or if that's necessary for the analysis to work properly. Here are two examples:

The front-end fails to parse a program that contains stride-based control:

def test_stride():
    @proc
    def foo(x: [R][3]):
        if stride(x, 0) == 1:
            pass
        else:
            pass

which fails with the following:

src/exo/API.py:53: in proc
    return Procedure(parser.result())
src/exo/API.py:175: in __init__
    proc = InferEffects(proc).result()
src/exo/effectcheck.py:91: in __init__
    body, eff = self.map_stmts(self.orig_proc.body)
src/exo/effectcheck.py:135: in map_stmts
    new_s = self.map_s(s)
src/exo/effectcheck.py:185: in map_s
    orelse_effects = eff_filter(cond.negate(), orelse_effects)
src/exo/LoopIR_effects.py:150: in negate
    return negate_expr(self)
>                   assert False, "TODO: add != support explicitly..."
E                   AssertionError: TODO: add != support explicitly...

Using specialize:

def test_specialize_stride():
    @proc
    def foo(x: [R][3]):
        pass
    foo = specialize(foo, foo.body()[0], "stride(x, 0) == 1")
    print(foo)

which will fail with:

src/exo/API_scheduling.py:101: in __call__
    return self.func(*bound_args.args, **bound_args.kwargs)
src/exo/API_scheduling.py:2266: in specialize
    ir, fwd = scheduling.DoSpecialize(block._impl, conds)
exo.new_eff.SchedulingError: <<<unknown directive>>>: Invalid specialization condition.