Struct cranelift_codegen::dominator_tree::DominatorTree

pub struct DominatorTree { /* fields omitted */ }

The dominator tree for a single function.

Implementations

impl DominatorTree

Methods for querying the dominator tree.

pub fn is_reachable(&self, block: Block) -> bool

Is block reachable from the entry block?

pub fn cfg_postorder(&self) -> &[Block]

Get the CFG post-order of blocks that was used to compute the dominator tree.

Note that this post-order is not updated automatically when the CFG is modified. It is computed from scratch and cached by compute().

pub fn idom(&self, block: Block) -> Option<Inst>

Returns the immediate dominator of block.

The immediate dominator of a basic block is a basic block which we represent by the branch or jump instruction at the end of the basic block. This does not have to be the terminator of its block.

A branch or jump is said to dominate block if all control flow paths from the function entry to block must go through the branch.

The immediate dominator is the dominator that is closest to block. All other dominators also dominate the immediate dominator.

This returns None if block is not reachable from the entry block, or if it is the entry block which has no dominators.

pub fn rpo_cmp<A, B>(&self, a: A, b: B, layout: &Layout) -> Ordering where
    A: Into<ExpandedProgramPoint>,
    B: Into<ExpandedProgramPoint>, 

Compare two program points relative to a reverse post-order traversal of the control-flow graph.

Return Ordering::Less if a comes before b in the RPO.

If a and b belong to the same block, compare their relative position in the block.

pub fn dominates<A, B>(&self, a: A, b: B, layout: &Layout) -> bool where
    A: Into<ExpandedProgramPoint>,
    B: Into<ExpandedProgramPoint>, 

Returns true if a dominates b.

This means that every control-flow path from the function entry to b must go through a.

Dominance is ill defined for unreachable blocks. This function can always determine dominance for instructions in the same block, but otherwise returns false if either block is unreachable.

An instruction is considered to dominate itself.

pub fn last_dominator<B>(&self, a: Block, b: B, layout: &Layout) -> Option<Inst> where
    B: Into<ExpandedProgramPoint>, 

Find the last instruction in a that dominates b. If no instructions in a dominate b, return None.

pub fn common_dominator(
    &self,
    a: BlockPredecessor,
    b: BlockPredecessor,
    layout: &Layout
) -> BlockPredecessor

Compute the common dominator of two basic blocks.

Both basic blocks are assumed to be reachable.

impl DominatorTree

pub fn new() -> Self

Allocate a new blank dominator tree. Use compute to compute the dominator tree for a function.

pub fn with_function(func: &Function, cfg: &ControlFlowGraph) -> Self

Allocate and compute a dominator tree.

pub fn compute(&mut self, func: &Function, cfg: &ControlFlowGraph)

Reset and compute a CFG post-order and dominator tree.

pub fn clear(&mut self)

Clear the data structures used to represent the dominator tree. This will leave the tree in a state where is_valid() returns false.

pub fn is_valid(&self) -> bool

Check if the dominator tree is in a valid state.

Note that this doesn’t perform any kind of validity checks. It simply checks if the compute() method has been called since the last clear(). It does not check that the dominator tree is consistent with the CFG.