Module moore_svlog::ty[−][src]

Expand description

A generalized SystemVerilog type system.

This module covers all types that may arise in a SystemVerilog source file, plus some additional things like modules/interfaces to streamline the handling of hierarchical names and interface signals/modports throughout the compiler.

Packed Types

Packed types are the core types of SystemVerilog. They combine a core packed type with an optional sign and zero or more packed dimensions. The core packed types are:

Integer vector types: bit, logic, reg
Integer atom types: byte, shortint, int, longint, integer, time
Packed structs and unions
Enums
Packed named types
Packed type references

The packed dimensions can be:

Unsized ([])
Ranges ([x:y])

Packed types are implemented by the PackedType struct.

Unpacked Types

Unpacked types are a second level of types in SystemVerilog. They extend a core unpacked type with a variety of unpacked dimensions, depending on which syntactic construct generated the type (variable or otherwise). The core unpacked types are:

Packed types
Non-integer types: shortreal, real, realtime
Unpacked structs and unions
string, chandle, event
Virtual interfaces
Class types
Covergroups
Unpacked named types
Unpacked type references
Modules and interfaces

The unpacked dimensions are:

Unsized ([])
Arrays ([x])
Ranges ([x:y])
Associative ([T] or [*])
Queues ([$] or [$:x])

Unpacked types are implemented by the UnpackedType struct.

Simple Bit Vector Types

Some packed types may be converted into an equivalent Simple Bit Vector Type (SBVT), which has an identical bit pattern as the original type, but consists only of an integer vector type with a single optional packed dimension. An SBVT can be converted back into a packed type. SBVTs can be range-cast, which changes the width of their single dimension.

SBVTs track whether the original packed type explicitly had a dimension or used an integer atom type, or was named. When converting back to a packed type, the SBVT attempts to restore this information, depending on how many changes were applied.

Sign

All packed types have an associated sign, indicating whether they are signed or unsigned. The types have a default sign, which means that the sign may have been omitted in the source file. Packed types can be sign-cast, which changes only their sign.

Domain

All packed types consist of bits that can either carry two or four values. An aggregate type is two-valued iff all its constituent types are two-valued, otherwise it is four-valued. Packed types can be domain-cast, which changes only their value domain.