# MLIR

Multi-Level IR Compiler Framework

### func (::mlir::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.

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

Example:

// External function definitions.
func @abort()
func @scribble(i32, i64, memref<? x 128 x f32, #layout_map0>) -> f64

// A function that returns its argument twice:
func @count(%x: i64) -> (i64, i64)
attributes {fruit: "banana"} {
return %x, %x: i64, i64
}

// A function with an argument attribute
func @example_fn_arg(%x: i32 {swift.self = unit})

// A function with a result attribute
func @example_fn_result() -> (f64 {dialectName.attrName = 0 : i64})

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


#### Attributes: ¶

AttributeMLIR TypeDescription
sym_name::mlir::StringAttrstring attribute
type::mlir::TypeAttrany type attribute
sym_visibility::mlir::StringAttrstring attribute

### module (::mlir::ModuleOp) ¶

A top level container operation

Syntax:

operation ::= module ($sym_name^)? attr-dict-with-keyword$body


A module represents a top-level container operation. It contains a single SSACFG region containing a single block which can contain any operations. Operations within this region cannot implicitly capture values defined outside the module, i.e. Modules are IsolatedFromAbove. Modules have an optional symbol name which can be used to refer to them in operations.

Example:

module {
func @foo()
}


#### Attributes: ¶

AttributeMLIR TypeDescription
sym_name::mlir::StringAttrstring attribute
sym_visibility::mlir::StringAttrstring attribute

### module_terminator (::mlir::ModuleTerminatorOp) ¶

A pseudo op that marks the end of a module

Syntax:

operation ::= module_terminator attr-dict


module_terminator is a special terminator operation for the body of a module, it has no semantic meaning beyond keeping the body of a module well-formed.

### unrealized_conversion_cast (::mlir::UnrealizedConversionCastOp) ¶

An unrealized conversion from one set of types to another

Syntax:

operation ::= unrealized_conversion_cast ($inputs^ : type($inputs))? to type(\$outputs) attr-dict


An unrealized_conversion_cast operation represents an unrealized conversion from one set of types to another, that is used to enable the inter-mixing of different type systems. This operation should not be attributed any special representational or execution semantics, and is generally only intended to be used to satisfy the temporary intermixing of type systems during the conversion of one type system to another.

This operation may produce results of arity 1-N, and accept as input operands of arity 0-N.

Example:

// An unrealized 0-1 conversion. These types of conversions are useful in
// cases where a type is removed from the type system, but not all uses have
// been converted. For example, imagine we have a tuple type that is
// expanded to its element types. If only some uses of an empty tuple type
// instance are converted we still need an instance of the tuple type, but
// have no inputs to the unrealized conversion.
%result = unrealized_conversion_cast to !bar.tuple_type<>

// An unrealized 1-1 conversion.
%result1 = unrealized_conversion_cast %operand : !foo.type to !bar.lowered_type

// An unrealized 1-N conversion.
%results2:2 = unrealized_conversion_cast %tuple_operand : !foo.tuple_type<!foo.type, !foo.type> to !foo.type, !foo.type

// An unrealized N-1 conversion.
%result3 = unrealized_conversion_cast %operand, %operand : !foo.type, !foo.type to !bar.tuple_type<!foo.type, !foo.type>


#### Operands: ¶

OperandDescription
inputsany type

#### Results: ¶

ResultDescription
outputsany type