Enum midenc_hir::CallConv

#[repr(u8)]
pub enum CallConv {
    Fast = 0,
    SystemV = 1,
    Wasm = 2,
    Kernel = 3,
}

Represents the calling convention of a function.

Calling conventions are part of a program’s ABI (Application Binary Interface), and they define things such how arguments are passed to a function, how results are returned, etc. In essence, the contract between caller and callee is described by the calling convention of a function.

Importantly, it is perfectly normal to mix calling conventions. For example, the public API for a C library will use whatever calling convention is used by C on the target platform (for Miden, that would be SystemV). However, internally that library may use the Fast calling convention to allow the compiler to optimize more effectively calls from the public API to private functions. In short, choose a calling convention that is well-suited for a given function, to the extent that other constraints don’t impose a choice on you.

Variants

Fast = 0

This calling convention is what I like to call “chef’s choice” - the compiler chooses it’s own convention that optimizes for call performance.

As a result of this, it is not permitted to use this convention in externally linked functions, as the convention is unstable, and the compiler can’t ensure that the caller in another translation unit will use the correct convention.

SystemV = 1

The standard calling convention used for C on most platforms

Wasm = 2

A function which is using the WebAssembly Component Model “Canonical ABI”.

Kernel = 3

A function with this calling convention must be called using the syscall instruction. Attempts to call it with any other call instruction will cause a validation error. The one exception to this rule is when calling another function with the Kernel convention that is defined in the same module, which can use the standard call instruction.

Kernel functions may only be defined in a kernel Module.

In all other respects, this calling convention is the same as SystemV

Trait Implementations

impl Clone for CallConv

fn clone(&self) -> CallConv

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for CallConv

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for CallConv

fn default() -> CallConv

Returns the “default value” for a type.

impl Display for CallConv

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for CallConv

fn eq(&self, other: &CallConv) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for CallConv

impl Eq for CallConv

impl StructuralPartialEq for CallConv