Struct OperandStack

pub struct OperandStack { /* private fields */ }

This structure emulates the state of the VM’s operand stack while generating code from the SSA representation of a function.

In order to emit efficient and correct stack manipulation code, we must be able to reason about where values are on the operand stack at a given program point. This structure tracks what SSA values have been pushed on the operand stack, where they are on the stack relative to the top, and whether a given stack slot aliases multiple values.

In addition to the state tracked, this structure also has an API that mimics the stack manipulation instructions we can emit in the code generator, so that as we emit instructions and modify this structure at the same time, 1:1.

Implementations

impl OperandStack

pub fn rename(&mut self, n: usize, value: ValueRef)

Renames the nth operand from the top of the stack to value

The type is assumed to remain unchanged

pub fn find(&self, value: &ValueRef) -> Option<usize>

Searches for the position on the stack containing the operand corresponding to value.

NOTE: This function will panic if value is not on the stack

pub fn is_empty(&self) -> bool

Returns true if the operand stack is empty

pub fn raw_len(&self) -> usize

Returns the number of field elements on the stack

pub fn effective_index(&self, index: usize) -> usize

Returns the index in the actual runtime stack which corresponds to the first element of the operand at index.

pub fn effective_index_inclusive(&self, index: usize) -> usize

Returns the index in the actual runtime stack which corresponds to the last element of the operand at index.

pub fn len(&self) -> usize

Returns the number of operands on the stack

pub fn peek(&self) -> Option<&Operand>

Returns the operand on top of the stack, without consuming it

pub fn push<V: Into<Operand>>(&mut self, value: V)

Pushes an operand on top of the stack

pub fn pop(&mut self) -> Option<Operand>

Pops the operand on top of the stack

pub fn drop(&mut self)

Drops the top operand on the stack

pub fn dropn(&mut self, n: usize)

Drops the top n operands on the stack

pub fn dup(&mut self, n: usize)

Duplicates the operand in the nth position on the stack

If n is 0, duplicates the top of the stack.

pub fn swap(&mut self, n: usize)

Swaps the nth operand from the top of the stack, with the top of the stack

If n is 1, it swaps the first two operands on the stack.

NOTE: This function will panic if n is 0, or out of bounds.

pub fn movup(&mut self, n: usize)

Moves the nth operand to the top of the stack

If n is 1, this is equivalent to swap(1).

NOTE: This function will panic if n is 0, or out of bounds.

pub fn movdn(&mut self, n: usize)

Makes the operand on top of the stack, the nth operand on the stack

If n is 1, this is equivalent to swap(1).

NOTE: This function will panic if n is 0, or out of bounds.

pub fn iter(&self) -> impl DoubleEndedIterator<Item = &Operand>

Trait Implementations

impl Clone for OperandStack

fn clone(&self) -> OperandStack

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for OperandStack

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

Formats the value using the given formatter.

impl Default for OperandStack

fn default() -> Self

Returns the “default value” for a type.

impl Index<usize> for OperandStack

type Output = Operand

The returned type after indexing.

fn index(&self, index: usize) -> &Self::Output

Performs the indexing (container[index]) operation.

impl IndexMut<usize> for OperandStack

fn index_mut(&mut self, index: usize) -> &mut Self::Output

Performs the mutable indexing (container[index]) operation.

impl PartialEq for OperandStack

fn eq(&self, other: &OperandStack) -> 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 Eq for OperandStack

impl StructuralPartialEq for OperandStack