'systemc' Dialect

Types and operations for the SystemC dialect

This dialect defines the systemc dialect, which represents various constructs of the SystemC library (IEEE 1666-2011) useful for emission.

Operations

systemc.convert (::circt::systemc::ConvertOp)

Converts between various integer and bit vector types.

Syntax:

operation ::= `systemc.convert` $input attr-dict `:` functional-type($input, $result)

Allows conversions between the various integer and bit vector types in SystemC, including MLIRs signless integers that are used to represent the primitive C integer types, according to the explicit and implicit constructors, implicit access operators and explicit conversion member functions defined in the respective data type class in the SystemC spec (refer to the description of the supported types and the spec chapters listed there for more information).

Traits: AlwaysSpeculatableImplTrait

Interfaces: ConditionallySpeculatable, NoMemoryEffect (MemoryEffectOpInterface)

Effects: MemoryEffects::Effect{}

Operands:

Results:

systemc.cpp.assign (::circt::systemc::AssignOp)

A C++ assignment.

Syntax:

operation ::= `systemc.cpp.assign` $dest `=` $source attr-dict `:` type($dest)

Assigns one SSA value to another. Note that there is no notion of lvalues and rvalues. This means that one can assign to a value that is the result of, e.g., an addition, which is not allowed in C++. It is the responsibility of the user and the implementor of a lowering pass that creates this operation to make sure that the operands are valid according to C++ semantics. Rationale for that: implementing these constraints would add quite some complexity, but still does not guarantee that the assignment is valid because we also make use of non-verifyable verbatim types, etc.

Traits: SameTypeOperands

Operands:

systemc.cpp.call (::circt::systemc::CallOp)

Call operation

Syntax:

operation ::= `systemc.cpp.call` $callee `(` $callee_operands `)` attr-dict `:`
              functional-type($callee_operands, $results)

The systemc.cpp.call operation represents a direct call to a function that is within the same symbol scope as the call. The operands and result types of the call must match the specified function type. The callee is encoded as a symbol reference attribute named “callee”.

Example:

%2 = systemc.cpp.call @my_add(%0, %1) : (i32, i32) -> i32

Interfaces: CallOpInterface, SymbolUserOpInterface

Attributes:

Operands:

Results:

systemc.cpp.call_indirect (::circt::systemc::CallIndirectOp)

Indirect call operation

Syntax:

operation ::= `systemc.cpp.call_indirect` $callee `(` $callee_operands `)` attr-dict `:` type($callee)

The systemc.cpp.call_indirect operation represents an indirect call to a value of function type. The operands and result types of the call must match the specified function type.

Example:

%func = systemc.cpp.member_access %object dot "func" : () -> i32
%result = systemc.cpp.call_indirect %func() : () -> i32

Interfaces: CallOpInterface

Operands:

Results:

systemc.cpp.delete (::circt::systemc::DeleteOp)

A C++ delete expression.

Syntax:

operation ::= `systemc.cpp.delete` $pointer attr-dict `:` qualified(type($pointer))

Destroys objects previously allocated by the new expression and releases the allocated memory.

Operands:

systemc.cpp.destructor (::circt::systemc::DestructorOp)

A C++ destructor definition.

Syntax:

operation ::= `systemc.cpp.destructor` attr-dict-with-keyword $body

This operation models a C++ destructor of a class or struct. It is not an operation modelling some abstract SystemC construct, but still required to support more complex functionality such as having a pointer to an external object inside a SystemC module, e.g., for interoperability purposes.

Traits: HasParent<SCModuleOp>, NoTerminator, SingleBlock

systemc.cpp.func (::circt::systemc::FuncOp)

An operation with a name containing a single SSACFG region

Operations within the function cannot implicitly capture values defined outside of the function, i.e. Functions are IsolatedFromAbove. All external references must use function arguments or attributes that establish a symbolic connection (e.g. symbols referenced by name via a string attribute like SymbolRefAttr). An external function declaration (used when referring to a function declared in some other module) has no body. While the MLIR textual form provides a nice inline syntax for function arguments, they are internally represented as “block arguments” to the first block in the region.

Argument names are stored in a ‘argNames’ attribute, but used directly as the SSA value’s names. They are verified to be unique and can be used to print them, e.g., as C function argument names.

Only dialect attribute names may be specified in the attribute dictionaries for function arguments, results, or the function itself.

Example:

// External function definitions.
systemc.cpp.func @abort()
systemc.cpp.func externC @scribble(i32, i64) -> i64

// A function that returns its argument twice:
systemc.cpp.func @count(%argumentName: i64) -> (i64, i64) {
  return %argumentName, %argumentName: i64, i64
}

// A function with an attribute
systemc.cpp.func @exampleFnAttr() attributes {dialectName.attrName = false}

Traits: AutomaticAllocationScope, IsolatedFromAbove

Interfaces: CallableOpInterface, FunctionOpInterface, OpAsmOpInterface, Symbol

Attributes:

systemc.cpp.member_access (::circt::systemc::MemberAccessOp)

A C++ member access expression.

Syntax:

operation ::= `systemc.cpp.member_access` $object $accessKind $memberName attr-dict `:`
              functional-type($object, $result)

Represents the C++ member access operators . and ->. The member name is passed as a plain string and is not checked for validity. Additional qualifications (A::E1) or template disambiguation (template E1) can be manually added to this plain member name string for emission. The type of the object and result cannot be verified as it is allowed to use varbatim types such as emitc.opaque.

Traits: AlwaysSpeculatableImplTrait

Interfaces: ConditionallySpeculatable, NoMemoryEffect (MemoryEffectOpInterface)

Effects: MemoryEffects::Effect{}

Attributes:

Operands:

Results:

systemc.cpp.new (::circt::systemc::NewOp)

A C++ ’new’ expression.

Syntax:

operation ::= `systemc.cpp.new` `(` $args `)` attr-dict `:` functional-type($args, $result)

Creates and initializes C++ objects using dynamic storage. Note that the types of the constructor arguments are not verified in any way w.r.t. the result’s type because it is allowed to use an opaque type for the pointee.

Traits: AlwaysSpeculatableImplTrait

Interfaces: ConditionallySpeculatable, NoMemoryEffect (MemoryEffectOpInterface)

Effects: MemoryEffects::Effect{}

Operands:

Results:

systemc.cpp.return (::circt::systemc::ReturnOp)

Function return operation

Syntax:

operation ::= `systemc.cpp.return` attr-dict ($returnValues^ `:` type($returnValues))?

The systemc.cpp.return operation represents a return operation within a function. The operand number and types must match the signature of the function that contains the operation.

Example:

systemc.cpp.func @foo() : i32 {
  ...
  systemc.cpp.return %0 : i32
}

Traits: AlwaysSpeculatableImplTrait, HasParent<systemc::FuncOp>, ReturnLike, Terminator

Interfaces: ConditionallySpeculatable, NoMemoryEffect (MemoryEffectOpInterface), RegionBranchTerminatorOpInterface

Effects: MemoryEffects::Effect{}

Operands:

systemc.cpp.variable (::circt::systemc::VariableOp)

Declare a C++ variable with optional initialization value.

Declares a variable according to C++ semantics. If an initialization value is present, the variable will be assigned that value at the declaration, e.g, int varname = 0;.

Interfaces: HasCustomSSAName, SystemCNameDeclOpInterface

Attributes:

Operands:

Results:

systemc.ctor (::circt::systemc::CtorOp)

A constructor definition.

Syntax:

operation ::= `systemc.ctor` attr-dict-with-keyword $body

Represents the SC_CTOR macro as described in IEEE 1666-2011 §5.2.7. The name of the module being constructed does not have to be passed to this operation, but is automatically added during emission.

Traits: HasParent<SCModuleOp>, NoTerminator, SingleBlock

systemc.func (::circt::systemc::SCFuncOp)

A (void)->void member function of a SC_MODULE.

Syntax:

operation ::= `systemc.func` `` custom<ImplicitSSAName>($name) attr-dict-with-keyword $body

This operation does not represent a specific SystemC construct, but a regular C++ member function with no arguments and a void return type. These are used to implement module-internal logic and are registered to the module using the SC_METHOD, SC_THREAD, and SC_CTHREAD macros.

Traits: HasParent<SCModuleOp>, NoTerminator, SingleBlock

Interfaces: HasCustomSSAName, InferTypeOpInterface, SystemCNameDeclOpInterface

Attributes:

Results:

systemc.instance.bind_port (::circt::systemc::BindPortOp)

Binds a port of a module instance to a channel.

The ports of a submodule have to be bound to channels in a module further up in the instance hierarchy (as opposed to sc_export where the channel has to reside in the same module or a submodule). Therefore, a port can be bound to either a signal declared by the systemc.signal operation or to a port with matching direction (and thus bound to a channel further up in the hierarchy). More information on ports can be found in IEEE 1666-2011 §5.12., in particular IEEE 1666-2011 §5.12.7. is about port binding. More information on predefined channels can be found in IEEE 1666-2011 §6.

Traits: HasParent<CtorOp>

Attributes:

Operands:

systemc.instance.decl (::circt::systemc::InstanceDeclOp)

Declares a SystemC module instance.

Syntax:

operation ::= `systemc.instance.decl` custom<ImplicitSSAName>($name) $moduleName attr-dict
              `:` qualified(type($instanceHandle))

Declares an instantiation of a SystemC module inside another SystemC module by value. The instance handle returned by this operation can then be used to initialize it in the constructor and to access its fields. More information can be found in IEEE 1666-2011 §4.1.1.

Traits: HasParent<SCModuleOp>

Interfaces: HasCustomSSAName, InstanceOpInterface, SymbolUserOpInterface, SystemCNameDeclOpInterface

Attributes:

Results:

systemc.interop.verilated (::circt::systemc::InteropVerilatedOp)

Instantiates a verilated module.

Syntax:

operation ::= `systemc.interop.verilated` $instanceName $moduleName
              custom<InputPortList>($inputs, type($inputs), $inputNames) `->`
              custom<OutputPortList>(type($results), $resultNames) attr-dict

Instantiates a verilated module represented by a hw.module operation (usually the extern variant).

This operation also encodes the interoparability layer to connect its context (i.e. the surrounding operation, input values, result values, and types) to the C++ code of the verilated module. When residing in a context that understands C++ (e.g., inside a SystemC module), this refers to the instantiation of the class, assignment of the input ports, the call to the eval() function and reading the output ports.

Additionally, properties of the verilated module can be specified in a config attribute which influences the interop layer code generation (not yet implemented).

Interfaces: OpAsmOpInterface, SymbolUserOpInterface

Attributes:

Operands:

Results:

systemc.method (::circt::systemc::MethodOp)

Represents the SystemC SC_METHOD macro.

Syntax:

operation ::= `systemc.method` $funcHandle attr-dict

Represents the SC_METHOD macro as described in IEEE 1666-2011 §5.2.9.

Operands:

systemc.module (::circt::systemc::SCModuleOp)

Define a SystemC SC_MODULE.

Represents the SC_MODULE macro as described in IEEE 1666-2011 §5.2.5. Models input, output and inout ports as module arguments (as opposed to sc_signals which are modeled by a separate systemc.signal operation), but are nonetheless emitted as regular struct fields.

Traits: HasParent<mlir::ModuleOp>, IsolatedFromAbove, NoTerminator, SingleBlock

Interfaces: CallableOpInterface, FunctionOpInterface, ModuleOpInterface, OpAsmOpInterface, RegionKindInterface, Symbol

Attributes:

systemc.sensitive (::circt::systemc::SensitiveOp)

Describes the static sensitivity of an unspawned process.

Syntax:

operation ::= `systemc.sensitive` $sensitivities attr-dict ( `:` qualified(type($sensitivities))^ )?

This operation allows to specify the static sensitivity of unspawned processes. An unspawned process is one created by the SC_METHOD, SC_THREAD, or SC_CTHREAD macro. The operands to this operation are registered as sensitivities to the process last created (in control-flow order). Each SC_MODULE contains an instance of the sc_sensitive class to do the registration. For a description of the sc_sensitive class refer to IEEE 1666-2011 §5.4. For a description of the sensitive data member of SC_MODULE refer to IEEE 1666-2011 §5.2.14.

Traits: HasParent<CtorOp>

Operands:

systemc.signal (::circt::systemc::SignalOp)

Declares a SystemC sc_signal<T>.

Syntax:

operation ::= `systemc.signal` custom<ImplicitSSAName>($name) ( `named` $named^ )? attr-dict
              `:` qualified(type($signal))

Represents the sc_signal template as described in IEEE 1666-2011 §6.4. Adding the ’named’ attribute will lead to the signal being emitted with the SC_NAMED convenience macro. Note that this macro is not part of IEEE 1666-2011, but was added in version 2.3.3.

Traits: HasParent<SCModuleOp>

Interfaces: HasCustomSSAName, SystemCNameDeclOpInterface

Attributes:

Results:

systemc.signal.read (::circt::systemc::SignalReadOp)

Returns the current value of a signal or port.

Syntax:

operation ::= `systemc.signal.read` $input attr-dict `:` qualified(type($input))

Represents the member function const T& read() const; and operator operator const T& () const; of class sc_signal as described in IEEE 1666-2011 §6.4.7., of class sc_in as described in §6.8.3., and of class sc_inout as decribed in §6.10.3. It shall return the current value of the signal/port.

Traits: AlwaysSpeculatableImplTrait

Interfaces: ConditionallySpeculatable, InferTypeOpInterface, NoMemoryEffect (MemoryEffectOpInterface)

Effects: MemoryEffects::Effect{}

Operands:

Results:

systemc.signal.write (::circt::systemc::SignalWriteOp)

Writes a value to a signal or port.

Syntax:

operation ::= `systemc.signal.write` $dest `,` $src attr-dict `:` qualified(type($dest))

Represents the member function void write(const T&); and several variants of the operator operator= of class sc_signal as described in IEEE 1666-2011 §6.4.8., of class sc_inout as described in §6.10.3., and of class sc_out as decribed in §6.12.3. It shall modify the value of the signal/port such that it appears to have the new value (as observed using the sytemc.signal.read operation) in the next delta cycle but not before then.

Operands:

systemc.thread (::circt::systemc::ThreadOp)

Represents the SystemC SC_THREAD macro.

Syntax:

operation ::= `systemc.thread` $funcHandle attr-dict

Represents the SC_THREAD macro as described in IEEE 1666-2011 §5.2.9.

Operands:

Type constraints

a SystemC sc_bigint type

a SystemC sc_biguint type

a SystemC sc_bv_base type

a SystemC sc_bv type

a SystemC sc_int_base type

a SystemC sc_int type

a SystemC sc_lv_base type

a SystemC sc_lv type

FunctionType with no inputs and results

a SystemC sc_signed type

a SystemC sc_uint_base type

a SystemC sc_uint type

a SystemC sc_unsigned type

a SystemC sc_value_base type

Types

InOutType

A SystemC sc_inout type

Syntax:

!systemc.inout<
  ::mlir::Type   # baseType
>

Represents the specialized SystemC port class sc_inout as described in IEEE 1666-2011 §6.10.

Parameters:

InputType

A SystemC sc_in type

Syntax:

!systemc.in<
  ::mlir::Type   # baseType
>

Represents the specialized SystemC port class sc_in as described in IEEE 1666-2011 §6.8.

Parameters:

LogicType

A SystemC sc_logic type

Syntax: !systemc.logic

Represents a single bit with with a value corresponding to one of the four logic states ‘0’, ‘1’, ‘Z’, and ‘X’ in SystemC as described in IEEE 1666-2011 §7.9.2. A value of this type can be created using the ’emitc.constant’ operation with a string attribute containing “0”, “1”, “X”, “Z”, “x”, or “z” or an i1 attribute representing “true” or “false”. Any other value will be interpreted as ‘X’ (unknown state).

ModuleType

A SystemC module type

Represents a SystemC module instantiation. Example: !systemc.module<moduleName(portName1: type1, portName2: type2)>

Parameters:

OutputType

A SystemC sc_out type

Syntax:

!systemc.out<
  ::mlir::Type   # baseType
>

Represents the specialized SystemC port class sc_out as described in IEEE 1666-2011 §6.12.

Parameters:

SignalType

A SystemC sc_signal type

Syntax:

!systemc.signal<
  ::mlir::Type   # baseType
>

Represents the predefined primitive channel sc_signal as described in IEEE 1666-2011 §6.4.

Parameters:

Enums

MemberAccessKind

C++ member access kind

Cases:

'systemc' Dialect Docs

• SystemC Dialect Rationale