Enum wasmtime_environ::ir::ArgumentPurpose

pub enum ArgumentPurpose {
    Normal,
    StructArgument(u32),
    StructReturn,
    Link,
    FramePointer,
    CalleeSaved,
    VMContext,
    SignatureId,
    StackLimit,
    CalleeTLS,
    CallerTLS,
}

The special purpose of a function argument.

Function arguments and return values are used to pass user program values between functions, but they are also used to represent special registers with significance to the ABI such as frame pointers and callee-saved registers.

The argument purpose is used to indicate any special meaning of an argument or return value.

Variants

Normal

A normal user program value passed to or from a function.

StructArgument(u32)

A C struct passed as argument.

StructReturn

Struct return pointer.

When a function needs to return more data than will fit in registers, the caller passes a pointer to a memory location where the return value can be written. In some ABIs, this struct return pointer is passed in a specific register.

This argument kind can also appear as a return value for ABIs that require a function with a StructReturn pointer argument to also return that pointer in a register.

Link

The link register.

Most RISC architectures implement calls by saving the return address in a designated register rather than pushing it on the stack. This is represented with a Link argument.

Similarly, some return instructions expect the return address in a register represented as a Link return value.

FramePointer

The frame pointer.

This indicates the frame pointer register which has a special meaning in some ABIs.

The frame pointer appears as an argument and as a return value since it is a callee-saved register.

CalleeSaved

A callee-saved register.

Some calling conventions have registers that must be saved by the callee. These registers are represented as CalleeSaved arguments and return values.

VMContext

A VM context pointer.

This is a pointer to a context struct containing details about the current sandbox. It is used as a base pointer for vmctx global values.

SignatureId

A signature identifier.

This is a special-purpose argument used to identify the calling convention expected by the caller in an indirect call. The callee can verify that the expected signature ID matches.

StackLimit

A stack limit pointer.

This is a pointer to a stack limit. It is used to check the current stack pointer against. Can only appear once in a signature.

CalleeTLS

A callee TLS value.

In the Baldrdash-2020 calling convention, the stack upon entry to the callee contains the TLS-register values for the caller and the callee. This argument is used to provide the value for the callee.

CallerTLS

A caller TLS value.

In the Baldrdash-2020 calling convention, the stack upon entry to the callee contains the TLS-register values for the caller and the callee. This argument is used to provide the value for the caller.

Trait Implementations

impl Clone for ArgumentPurpose

pub fn clone(&self) -> ArgumentPurpose

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for ArgumentPurpose

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for ArgumentPurpose

pub fn deserialize<__D>(
    __deserializer: __D
) -> Result<ArgumentPurpose, <__D as Deserializer<'de>>::Error> where
    __D: Deserializer<'de>, 

Deserialize this value from the given Serde deserializer.

impl Display for ArgumentPurpose

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

Formats the value using the given formatter.

impl FromStr for ArgumentPurpose

type Err = ()

The associated error which can be returned from parsing.

pub fn from_str(s: &str) -> Result<ArgumentPurpose, ()>

Parses a string s to return a value of this type.

impl Hash for ArgumentPurpose

pub fn hash<__H>(&self, state: &mut __H) where
    __H: Hasher, 

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl PartialEq<ArgumentPurpose> for ArgumentPurpose

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

This method tests for self and other values to be equal, and is used by ==.

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

This method tests for !=.

impl Serialize for ArgumentPurpose

pub fn serialize<__S>(
    &self,
    __serializer: __S
) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error> where
    __S: Serializer, 

Serialize this value into the given Serde serializer.

impl Copy for ArgumentPurpose

impl Eq for ArgumentPurpose

impl StructuralEq for ArgumentPurpose

impl StructuralPartialEq for ArgumentPurpose