- adds handling of zero-sized types for volatile_store.
- adds type size checks and warnigns for other volatile intrinsics.
- adds a test to check warnings emitting.
Cause of the issue
While preparing for trans_intrinsic_call() invoke arguments are
processed with trans_argument() method which excludes zero-sized types
from argument list (to be more correct - all arguments for which
ArgKind is Ignore are filtered out). As result volatile_store() intrinsic
gets one argument instead of expected address and value.
How it is fixed
Modification of the trans_argument() method may cause side effects,
therefore change was implemented in volatile_store() intrinsic building
code itself. Now it checks function signature and if it was specialised
with zero-sized type, then emits C_nil() instead of accessing
non-existing second argument.
Additionally warnings are added for all volatile operations which are
specialised with zero-sized arguments. In fact, those operations are omitted
in LLVM backend if no memory affected at all, e.g. number of elements
is zero or type is zero-sized. This was not explicitly documented before
and could lead to potential issues if developer expects volatile behaviour,
but type has degraded to zero-sized.
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