Struct StackScheduler 

pub struct StackScheduler {
    pub stack: StackModel,
    pub spills: SpillManager,
    /* private fields */
}

Stack scheduler that generates stack manipulation operations.

Fields

stack: StackModel

Current stack state.

spills: SpillManager

Spill manager for values beyond stack depth 16.

Implementations

impl StackScheduler

pub fn new() -> StackScheduler

Creates a new stack scheduler.

pub fn clear_ops(&mut self)

Clears the scheduled operations (after emitting them).

pub fn take_ops(&mut self) -> Vec<ScheduledOp>

Takes the scheduled operations.

pub fn ensure_on_top( &mut self, value: ValueId, func: &Function, ) -> &[ScheduledOp]

Ensures a value is on top of the stack. Returns the operations needed to achieve this.

pub fn ensure_operand_on_top( &mut self, value: ValueId, func: &Function, ) -> &[ScheduledOp]

Emits a fresh operand occurrence for a consuming instruction.

If value is already on top, ensure_on_top can claim that existing stack item. That is correct for a single use, but wrong for instructions that consume the same MIR value more than once, such as revert(x, x) or log1(x, x, x). In those cases every operand occurrence needs its own stack item, so a top-of-stack value must be duplicated.

pub fn can_emit_value(&self, value: ValueId, func: &Function) -> bool

Checks if we can emit a value (it’s an immediate, arg, on stack, or spilled). Returns false for instruction results that aren’t tracked.

pub fn ensure_on_top_many( &mut self, values: &[ValueId], func: &Function, ) -> Vec<ScheduledOp>

Ensures multiple values are on top of the stack in order. The first value will be at the top, second below it, etc.

pub fn bring_to_top(&mut self, value: ValueId) -> Option<StackOp>

Brings a specific value to the top of the stack using SWAP. The value must already be on the stack within accessible range.

pub fn instruction_executed( &mut self, consumed: usize, produced: Option<ValueId>, )

Records that an instruction consumed its operands and produced a result. This updates the stack model accordingly.

pub fn instruction_executed_untracked(&mut self, consumed: usize)

Records that an instruction consumed inputs and produced an untracked output. The output is on the EVM stack but we don’t track which ValueId it corresponds to. This is used for MLOAD where the value may become stale in loops.

pub fn has_untracked_on_top(&self) -> bool

Checks if there’s an untracked value on top of the stack.

pub fn has_untracked_at_depth(&self, depth: usize) -> bool

Checks if there’s an untracked value at a specific depth.

pub fn stack_swapped(&mut self)

Records that a SWAP1 was executed, updating the stack model.

pub fn drop_dead_values( &mut self, liveness: &Liveness, block: BlockId, inst_idx: usize, ) -> Vec<StackOp>

Drops dead values from the stack. Returns operations (SWAPs and POPs) to remove dead values.

pub fn spill_excess_values(&mut self) -> Vec<ScheduledOp>

Spills values to memory to make room on the stack. This is needed when stack depth exceeds 16.

pub fn stack_depth(&self) -> usize

Returns the current stack depth.

pub fn depth(&self) -> usize

Returns the current stack depth (alias for stack_depth).

pub fn clear_stack(&mut self)

Clears the stack model (used at block boundaries).

pub fn shuffle_to_layout(&mut self, target: &[TargetSlot]) -> ShuffleResult

Shuffles the current stack to match the target layout.

This uses the backward layout optimization approach:

• Given a target layout (what we want the stack to look like)
• Generate the minimal sequence of DUP/SWAP/POP operations

Returns the shuffle result containing the operations to emit.

pub fn prepare_binary_op( &mut self, a: ValueId, b: ValueId, _func: &Function, ) -> ShuffleResult

Prepares the stack for a binary operation.

Given operands (a, b) where a should be on top and b below:

• Computes the target layout [a, b, …rest]
• Shuffles current stack to match
• Returns operations to emit

pub fn prepare_unary_op( &mut self, operand: ValueId, _func: &Function, ) -> ShuffleResult

Prepares the stack for a unary operation.

Given operand that should be on top:

• Computes the target layout [operand, …rest]
• Shuffles current stack to match
• Returns operations to emit

pub fn compute_binary_entry_layout( a: ValueId, b: ValueId, result: Option<ValueId>, exit_layout: &[TargetSlot], ) -> Vec<TargetSlot>

Computes the ideal entry layout for a binary operation given the exit layout.

For ADD(a, b) -> result, if exit layout is [result, x, y]:

• Entry layout should be [a, b, x, y]

pub fn compute_unary_entry_layout( operand: ValueId, result: Option<ValueId>, exit_layout: &[TargetSlot], ) -> Vec<TargetSlot>

Computes the ideal entry layout for a unary operation given the exit layout.

pub fn set_block_entry_layout( &mut self, block: BlockId, layout: BlockStackLayout, )

Sets the entry layout for a block.

This is used to specify what the stack should look like when entering a block. Predecessors will shuffle their stacks to match this layout.

pub fn get_block_entry_layout( &self, block: BlockId, ) -> Option<&BlockStackLayout>

Gets the entry layout for a block, if one has been set.

pub fn record_block_exit_layout(&mut self, block: BlockId)

Records the exit layout for a block (current stack state).

This is called after generating a block’s instructions, before the terminator. The layout is used to determine what values are on the stack when exiting.

pub fn get_block_exit_layout(&self, block: BlockId) -> Option<&BlockStackLayout>

Gets the exit layout for a block, if one has been recorded.

pub fn compute_merge_layout( &self, predecessors: &[BlockId], live_in: impl IntoIterator<Item = ValueId>, ) -> BlockStackLayout

Computes the entry layout for a merge block from its predecessors’ exit layouts.

This is the key function for phi node handling. It finds a common stack layout that all predecessors can shuffle to with minimal cost.

The function also considers the live-in values for the block to ensure all needed values are on the stack.

pub fn shuffle_to_block_entry(&mut self, target_block: BlockId) -> ShuffleResult

Shuffles the current stack to match a block’s entry layout.

Returns the shuffle operations needed. The caller is responsible for emitting the actual opcodes.

pub fn init_from_block_entry_layout(&mut self, block: BlockId)

Initializes the stack from a block’s entry layout.

This is called when starting to generate a block that has an entry layout. It sets up the stack model to match the expected entry state.

pub fn clear_block_layouts(&mut self)

Clears all block layout information.

Called when starting to generate a new function.

pub fn has_block_entry_layout(&self, block: BlockId) -> bool

Returns true if a block has an entry layout set.

pub fn stack_matches_entry_layout(&self, target_block: BlockId) -> bool

Checks if the current stack matches a block’s entry layout.

Returns true if the stack already matches the target layout (no shuffling needed).

Trait Implementations

impl Default for StackScheduler

fn default() -> StackScheduler

Returns the “default value” for a type.