Question

Imported and exported function arguments are generally passed by some form of a reference, with the exception of small values of SystemVerilog input arguments (see Annex E.11.7), which are passed by value. Similarly, the function result, which is restricted to small values, is passed by value, i.e., directly returned.

Actual arguments passed by reference typically are passed without changing their representation from the one used by a simulator. There is no inherent copying of arguments (other than any copying resulting from coercing).

Access to packed arrays via canonical representation involves copying arguments and does incur some overhead, however. Alternatively, for the sake of performance the application can be tuned for a particular tool and access the packed arrays directly through pointers using implementation representation, which could compromise binary and/or source compatibility. Data can be, however, moved around (copied, stored, retrieved) without using canonical representation while preserving binary or source level compatibility at the same time. This is possible by using pointers and size of data and when the detailed knowledge of the data representation is not required.

NOTE—This provides some degree of flexibility and allows the user to control the trade-off of performance vs. portability.

Formal arguments, except open arrays, are passed by direct reference or value, and, therefore, are directly accessible in C code. Formal arguments declared in SystemVerilog as open arrays are passed by a handle (type svOpenArrayHandle) and are accessible via library functions.