Struct libfirm_rs::nodes::Bad

pub struct Bad(_);

Bad nodes indicate invalid input, which is values which should never be computed.

The typical use case for the Bad node is removing unreachable code. Frontends should set the current_block to Bad when it is clear that following code must be unreachable (i.e. after a goto or return statement). Optimizations also set block predecessors to Bad when it becomes clear, that a control flow edge can never be executed.

The gigo optimizations ensures that nodes with Bad as their block, get replaced by Bad themselves. Nodes with at least 1 Bad input get exchanged with Bad too. Exception to this rule are Block, Phi, Tuple and End node; This is because removing inputs from a Block is hairy operation (requiring, Phis to be shortened too for example). So instead of removing block inputs they are set to Bad, and the actual removal is left to the control flow optimization phase. Block, Phi, Tuple with only Bad inputs however are replaced by Bad right away.

In the future we may use the Bad node to model poison values that arise from undefined behaviour like reading uninitialized local variables in C.

Trait Implementations

impl NodeTrait for Bad

fn internal_ir_node(&self) -> *mut ir_node

fn as_node(&self) -> Node

fn keep_alive(&self)

fn mode(&self) -> Mode

fn block(&self) -> Block

fn set_block(&self, block: Block)

Important traits for OutNodeIterator

impl Iterator for OutNodeIterator type Item = Node;

fn out_nodes(&self) -> OutNodeIterator

Important traits for OutNodeExIterator

impl Iterator for OutNodeExIterator type Item = (Node, i32);

fn out_nodes_ex(&self) -> OutNodeExIterator

fn all_out_projs(&self) -> Vec<Proj>

fn collect_all_out_projs(&self, projs: &mut Vec<Proj>)

Important traits for InNodeIterator

impl Iterator for InNodeIterator type Item = Node;

fn in_nodes(&self) -> InNodeIterator

fn set_input_at(&self, idx: i32, pred: Node)

fn set_in_nodes(&self, nodes: &[Node])

fn node_id(&self) -> i64

fn is_pinned(&self) -> bool

fn is_commutative(&self) -> bool

fn is_only_valid_in_start_block(&self) -> bool

fn graph(&self) -> Graph

fn walk<F>(&self, walker: F) where     F: FnMut(VisitTime, Node),     Self: Sized,

libifrm irg_walk wrapper

fn walk_dfs_in_block_stop_at_phi_node<Callback>(     &self,     block: Block,     callback: &mut Callback ) where     Callback: FnMut(Node),     Self: Sized,

Perform a DFS over all nodes within block starting at self. As soon as a Phi node is reached, that branch of the DFS is canceled. There is no callback for a Phi node. The primary use case for this API is in codegen.

impl NodeDebug for Bad

fn fmt(&self, f: &mut Formatter, _opts: NodeDebugOpts) -> Result

fn debug_fmt(self) -> NodeDebugFmt<Self> where     Self: Sized + Copy,

impl PartialEq<Bad> for Bad

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

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

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

This method tests for !=.

impl From<Bad> for Node

fn from(node: Bad) -> Node

Performs the conversion.

impl Clone for Bad

fn clone(&self) -> Bad

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Copy for Bad

impl Eq for Bad

impl Debug for Bad

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

Formats the value using the given formatter.

impl Hash for Bad

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

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].