TemporaryMDNode

public class TemporaryMDNode : IRMetadata

Represents a temporary metadata node.

Temporary metadata nodes aid in the construction of cyclic metadata. The typical construction pattern is usually as follows:

// Allocate a temporary temp node
let temp = TemporaryMDNode(in: context, operands: [])
// Prepare the operands to the metadata node...
var ops = [IRMetadata]()
// ...
// Create the real node
let root = MDNode(in: context, operands: ops)

At this point we have the following metadata structure:

//   !0 = metadata !{}            <- temp
//   !1 = metadata !{metadata !0} <- root
// Replace the temp operand with the root node

The knot is tied by RAUW'ing the temporary node:

temp.replaceAllUses(with: root)
// We now have
//   !1 = metadata !{metadata !1} <- self-referential root

Warning

It is critical that temporary metadata nodes be “RAUW’d” (replace-all-uses-with) before the metadata graph is finalized. After that time, all remaining temporary metadata nodes will become unresolved metadata.

  • Declaration

    Swift

    required public init(llvm: LLVMMetadataRef)

  • Create a new temporary metadata node in the given context with the given operands.

    Declaration

    Swift

    public init(in context: Context = .global, operands: [IRMetadata])

    Parameters

    context

    The context to allocate the node in.
    operands

    The operands to attach to the metadata node.

  • Declaration

    Swift

    public func asMetadata() -> LLVMMetadataRef