//! A Dominator Tree represented as mappings of Blocks to their immediate dominator.
use crate::entity::SecondaryMap;
use crate::flowgraph::{BlockPredecessor, ControlFlowGraph};
use crate::ir::instructions::BranchInfo;
use crate::ir::{Block, ExpandedProgramPoint, Function, Inst, Layout, ProgramOrder, Value};
use crate::packed_option::PackedOption;
use crate::timing;
use alloc::vec::Vec;
use core::cmp;
use core::cmp::Ordering;
use core::mem;
/// RPO numbers are not first assigned in a contiguous way but as multiples of STRIDE, to leave
/// room for modifications of the dominator tree.
const STRIDE: u32 = 4;
/// Special RPO numbers used during `compute_postorder`.
const DONE: u32 = 1;
const SEEN: u32 = 2;
/// Dominator tree node. We keep one of these per block.
#[derive(Clone, Default)]
struct DomNode {
/// Number of this node in a reverse post-order traversal of the CFG, starting from 1.
/// This number is monotonic in the reverse postorder but not contiguous, since we leave
/// holes for later localized modifications of the dominator tree.
/// Unreachable nodes get number 0, all others are positive.
rpo_number: u32,
/// The immediate dominator of this block, represented as the branch or jump instruction at the
/// end of the dominating basic block.
///
/// This is `None` for unreachable blocks and the entry block which doesn't have an immediate
/// dominator.
idom: PackedOption<Inst>,
}
/// The dominator tree for a single function.
pub struct DominatorTree {
nodes: SecondaryMap<Block, DomNode>,
/// CFG post-order of all reachable blocks.
postorder: Vec<Block>,
/// Scratch memory used by `compute_postorder()`.
stack: Vec<Block>,
valid: bool,
}
/// Methods for querying the dominator tree.
impl DominatorTree {
/// Is `block` reachable from the entry block?
pub fn is_reachable(&self, block: Block) -> bool {
self.nodes[block].rpo_number != 0
}
/// 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 cfg_postorder(&self) -> &[Block] {
debug_assert!(self.is_valid());
&self.postorder
}
/// 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 idom(&self, block: Block) -> Option<Inst> {
self.nodes[block].idom.into()
}
/// Compare two blocks relative to the reverse post-order.
fn rpo_cmp_block(&self, a: Block, b: Block) -> Ordering {
self.nodes[a].rpo_number.cmp(&self.nodes[b].rpo_number)
}
/// 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 rpo_cmp<A, B>(&self, a: A, b: B, layout: &Layout) -> Ordering
where
A: Into<ExpandedProgramPoint>,
B: Into<ExpandedProgramPoint>,
{
let a = a.into();
let b = b.into();
self.rpo_cmp_block(layout.pp_block(a), layout.pp_block(b))
.then(layout.cmp(a, b))
}
/// 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 dominates<A, B>(&self, a: A, b: B, layout: &Layout) -> bool
where
A: Into<ExpandedProgramPoint>,
B: Into<ExpandedProgramPoint>,
{
let a = a.into();
let b = b.into();
match a {
ExpandedProgramPoint::Block(block_a) => {
a == b || self.last_dominator(block_a, b, layout).is_some()
}
ExpandedProgramPoint::Inst(inst_a) => {
let block_a = layout
.inst_block(inst_a)
.expect("Instruction not in layout.");
match self.last_dominator(block_a, b, layout) {
Some(last) => layout.cmp(inst_a, last) != Ordering::Greater,
None => false,
}
}
}
}
/// Find the last instruction in `a` that dominates `b`.
/// If no instructions in `a` dominate `b`, return `None`.
pub fn last_dominator<B>(&self, a: Block, b: B, layout: &Layout) -> Option<Inst>
where
B: Into<ExpandedProgramPoint>,
{
let (mut block_b, mut inst_b) = match b.into() {
ExpandedProgramPoint::Block(block) => (block, None),
ExpandedProgramPoint::Inst(inst) => (
layout.inst_block(inst).expect("Instruction not in layout."),
Some(inst),
),
};
let rpo_a = self.nodes[a].rpo_number;
// Run a finger up the dominator tree from b until we see a.
// Do nothing if b is unreachable.
while rpo_a < self.nodes[block_b].rpo_number {
let idom = match self.idom(block_b) {
Some(idom) => idom,
None => return None, // a is unreachable, so we climbed past the entry
};
block_b = layout.inst_block(idom).expect("Dominator got removed.");
inst_b = Some(idom);
}
if a == block_b {
inst_b
} else {
None
}
}
/// Compute the common dominator of two basic blocks.
///
/// Both basic blocks are assumed to be reachable.
pub fn common_dominator(
&self,
mut a: BlockPredecessor,
mut b: BlockPredecessor,
layout: &Layout,
) -> BlockPredecessor {
loop {
match self.rpo_cmp_block(a.block, b.block) {
Ordering::Less => {
// `a` comes before `b` in the RPO. Move `b` up.
let idom = self.nodes[b.block].idom.expect("Unreachable basic block?");
b = BlockPredecessor::new(
layout.inst_block(idom).expect("Dangling idom instruction"),
idom,
);
}
Ordering::Greater => {
// `b` comes before `a` in the RPO. Move `a` up.
let idom = self.nodes[a.block].idom.expect("Unreachable basic block?");
a = BlockPredecessor::new(
layout.inst_block(idom).expect("Dangling idom instruction"),
idom,
);
}
Ordering::Equal => break,
}
}
debug_assert_eq!(
a.block, b.block,
"Unreachable block passed to common_dominator?"
);
// We're in the same block. The common dominator is the earlier instruction.
if layout.cmp(a.inst, b.inst) == Ordering::Less {
a
} else {
b
}
}
}
impl DominatorTree {
/// Allocate a new blank dominator tree. Use `compute` to compute the dominator tree for a
/// function.
pub fn new() -> Self {
Self {
nodes: SecondaryMap::new(),
postorder: Vec::new(),
stack: Vec::new(),
valid: false,
}
}
/// Allocate and compute a dominator tree.
pub fn with_function(func: &Function, cfg: &ControlFlowGraph) -> Self {
let block_capacity = func.layout.block_capacity();
let mut domtree = Self {
nodes: SecondaryMap::with_capacity(block_capacity),
postorder: Vec::with_capacity(block_capacity),
stack: Vec::new(),
valid: false,
};
domtree.compute(func, cfg);
domtree
}
/// Reset and compute a CFG post-order and dominator tree.
pub fn compute(&mut self, func: &Function, cfg: &ControlFlowGraph) {
let _tt = timing::domtree();
debug_assert!(cfg.is_valid());
self.compute_postorder(func);
self.compute_domtree(func, cfg);
self.valid = true;
}
/// 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 clear(&mut self) {
self.nodes.clear();
self.postorder.clear();
debug_assert!(self.stack.is_empty());
self.valid = false;
}
/// 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.
pub fn is_valid(&self) -> bool {
self.valid
}
/// Reset all internal data structures and compute a post-order of the control flow graph.
///
/// This leaves `rpo_number == 1` for all reachable blocks, 0 for unreachable ones.
fn compute_postorder(&mut self, func: &Function) {
self.clear();
self.nodes.resize(func.dfg.num_blocks());
// This algorithm is a depth first traversal (DFT) of the control flow graph, computing a
// post-order of the blocks that are reachable form the entry block. A DFT post-order is not
// unique. The specific order we get is controlled by two factors:
//
// 1. The order each node's children are visited, and
// 2. The method used for pruning graph edges to get a tree.
//
// There are two ways of viewing the CFG as a graph:
//
// 1. Each block is a node, with outgoing edges for all the branches in the block.
// 2. Each basic block is a node, with outgoing edges for the single branch at the end of
// the BB. (An block is a linear sequence of basic blocks).
//
// The first graph is a contraction of the second one. We want to compute an block post-order
// that is compatible both graph interpretations. That is, if you compute a BB post-order
// and then remove those BBs that do not correspond to block headers, you get a post-order of
// the block graph.
//
// Node child order:
//
// In the BB graph, we always go down the fall-through path first and follow the branch
// destination second.
//
// In the block graph, this is equivalent to visiting block successors in a bottom-up
// order, starting from the destination of the block's terminating jump, ending at the
// destination of the first branch in the block.
//
// Edge pruning:
//
// In the BB graph, we keep an edge to an block the first time we visit the *source* side
// of the edge. Any subsequent edges to the same block are pruned.
//
// The equivalent tree is reached in the block graph by keeping the first edge to an block
// in a top-down traversal of the successors. (And then visiting edges in a bottom-up
// order).
//
// This pruning method makes it possible to compute the DFT without storing lots of
// information about the progress through an block.
// During this algorithm only, use `rpo_number` to hold the following state:
//
// 0: block has not yet been reached in the pre-order.
// SEEN: block has been pushed on the stack but successors not yet pushed.
// DONE: Successors pushed.
match func.layout.entry_block() {
Some(block) => {
self.stack.push(block);
self.nodes[block].rpo_number = SEEN;
}
None => return,
}
while let Some(block) = self.stack.pop() {
match self.nodes[block].rpo_number {
SEEN => {
// This is the first time we pop the block, so we need to scan its successors and
// then revisit it.
self.nodes[block].rpo_number = DONE;
self.stack.push(block);
self.push_successors(func, block);
}
DONE => {
// This is the second time we pop the block, so all successors have been
// processed.
self.postorder.push(block);
}
_ => unreachable!(),
}
}
}
/// Push `block` successors onto `self.stack`, filtering out those that have already been seen.
///
/// The successors are pushed in program order which is important to get a split-invariant
/// post-order. Split-invariant means that if an block is split in two, we get the same
/// post-order except for the insertion of the new block header at the split point.
fn push_successors(&mut self, func: &Function, block: Block) {
for inst in func.layout.block_insts(block) {
match func.dfg.analyze_branch(inst) {
BranchInfo::SingleDest(succ, _) => self.push_if_unseen(succ),
BranchInfo::Table(jt, dest) => {
for succ in func.jump_tables[jt].iter() {
self.push_if_unseen(*succ);
}
if let Some(dest) = dest {
self.push_if_unseen(dest);
}
}
BranchInfo::NotABranch => {}
}
}
}
/// Push `block` onto `self.stack` if it has not already been seen.
fn push_if_unseen(&mut self, block: Block) {
if self.nodes[block].rpo_number == 0 {
self.nodes[block].rpo_number = SEEN;
self.stack.push(block);
}
}
/// Build a dominator tree from a control flow graph using Keith D. Cooper's
/// "Simple, Fast Dominator Algorithm."
fn compute_domtree(&mut self, func: &Function, cfg: &ControlFlowGraph) {
// During this algorithm, `rpo_number` has the following values:
//
// 0: block is not reachable.
// 1: block is reachable, but has not yet been visited during the first pass. This is set by
// `compute_postorder`.
// 2+: block is reachable and has an assigned RPO number.
// We'll be iterating over a reverse post-order of the CFG, skipping the entry block.
let (entry_block, postorder) = match self.postorder.as_slice().split_last() {
Some((&eb, rest)) => (eb, rest),
None => return,
};
debug_assert_eq!(Some(entry_block), func.layout.entry_block());
// Do a first pass where we assign RPO numbers to all reachable nodes.
self.nodes[entry_block].rpo_number = 2 * STRIDE;
for (rpo_idx, &block) in postorder.iter().rev().enumerate() {
// Update the current node and give it an RPO number.
// The entry block got 2, the rest start at 3 by multiples of STRIDE to leave
// room for future dominator tree modifications.
//
// Since `compute_idom` will only look at nodes with an assigned RPO number, the
// function will never see an uninitialized predecessor.
//
// Due to the nature of the post-order traversal, every node we visit will have at
// least one predecessor that has previously been visited during this RPO.
self.nodes[block] = DomNode {
idom: self.compute_idom(block, cfg, &func.layout).into(),
rpo_number: (rpo_idx as u32 + 3) * STRIDE,
}
}
// Now that we have RPO numbers for everything and initial immediate dominator estimates,
// iterate until convergence.
//
// If the function is free of irreducible control flow, this will exit after one iteration.
let mut changed = true;
while changed {
changed = false;
for &block in postorder.iter().rev() {
let idom = self.compute_idom(block, cfg, &func.layout).into();
if self.nodes[block].idom != idom {
self.nodes[block].idom = idom;
changed = true;
}
}
}
}
// Compute the immediate dominator for `block` using the current `idom` states for the reachable
// nodes.
fn compute_idom(&self, block: Block, cfg: &ControlFlowGraph, layout: &Layout) -> Inst {
// Get an iterator with just the reachable, already visited predecessors to `block`.
// Note that during the first pass, `rpo_number` is 1 for reachable blocks that haven't
// been visited yet, 0 for unreachable blocks.
let mut reachable_preds = cfg
.pred_iter(block)
.filter(|&BlockPredecessor { block: pred, .. }| self.nodes[pred].rpo_number > 1);
// The RPO must visit at least one predecessor before this node.
let mut idom = reachable_preds
.next()
.expect("block node must have one reachable predecessor");
for pred in reachable_preds {
idom = self.common_dominator(idom, pred, layout);
}
idom.inst
}
}
/// Optional pre-order information that can be computed for a dominator tree.
///
/// This data structure is computed from a `DominatorTree` and provides:
///
/// - A forward traversable dominator tree through the `children()` iterator.
/// - An ordering of blocks according to a dominator tree pre-order.
/// - Constant time dominance checks at the block granularity.
///
/// The information in this auxiliary data structure is not easy to update when the control flow
/// graph changes, which is why it is kept separate.
pub struct DominatorTreePreorder {
nodes: SecondaryMap<Block, ExtraNode>,
// Scratch memory used by `compute_postorder()`.
stack: Vec<Block>,
}
#[derive(Default, Clone)]
struct ExtraNode {
/// First child node in the domtree.
child: PackedOption<Block>,
/// Next sibling node in the domtree. This linked list is ordered according to the CFG RPO.
sibling: PackedOption<Block>,
/// Sequence number for this node in a pre-order traversal of the dominator tree.
/// Unreachable blocks have number 0, the entry block is 1.
pre_number: u32,
/// Maximum `pre_number` for the sub-tree of the dominator tree that is rooted at this node.
/// This is always >= `pre_number`.
pre_max: u32,
}
/// Creating and computing the dominator tree pre-order.
impl DominatorTreePreorder {
/// Create a new blank `DominatorTreePreorder`.
pub fn new() -> Self {
Self {
nodes: SecondaryMap::new(),
stack: Vec::new(),
}
}
/// Recompute this data structure to match `domtree`.
pub fn compute(&mut self, domtree: &DominatorTree, layout: &Layout) {
self.nodes.clear();
debug_assert_eq!(self.stack.len(), 0);
// Step 1: Populate the child and sibling links.
//
// By following the CFG post-order and pushing to the front of the lists, we make sure that
// sibling lists are ordered according to the CFG reverse post-order.
for &block in domtree.cfg_postorder() {
if let Some(idom_inst) = domtree.idom(block) {
let idom = layout.pp_block(idom_inst);
let sib = mem::replace(&mut self.nodes[idom].child, block.into());
self.nodes[block].sibling = sib;
} else {
// The only block without an immediate dominator is the entry.
self.stack.push(block);
}
}
// Step 2. Assign pre-order numbers from a DFS of the dominator tree.
debug_assert!(self.stack.len() <= 1);
let mut n = 0;
while let Some(block) = self.stack.pop() {
n += 1;
let node = &mut self.nodes[block];
node.pre_number = n;
node.pre_max = n;
if let Some(n) = node.sibling.expand() {
self.stack.push(n);
}
if let Some(n) = node.child.expand() {
self.stack.push(n);
}
}
// Step 3. Propagate the `pre_max` numbers up the tree.
// The CFG post-order is topologically ordered w.r.t. dominance so a node comes after all
// its dominator tree children.
for &block in domtree.cfg_postorder() {
if let Some(idom_inst) = domtree.idom(block) {
let idom = layout.pp_block(idom_inst);
let pre_max = cmp::max(self.nodes[block].pre_max, self.nodes[idom].pre_max);
self.nodes[idom].pre_max = pre_max;
}
}
}
}
/// An iterator that enumerates the direct children of an block in the dominator tree.
pub struct ChildIter<'a> {
dtpo: &'a DominatorTreePreorder,
next: PackedOption<Block>,
}
impl<'a> Iterator for ChildIter<'a> {
type Item = Block;
fn next(&mut self) -> Option<Block> {
let n = self.next.expand();
if let Some(block) = n {
self.next = self.dtpo.nodes[block].sibling;
}
n
}
}
/// Query interface for the dominator tree pre-order.
impl DominatorTreePreorder {
/// Get an iterator over the direct children of `block` in the dominator tree.
///
/// These are the block's whose immediate dominator is an instruction in `block`, ordered according
/// to the CFG reverse post-order.
pub fn children(&self, block: Block) -> ChildIter {
ChildIter {
dtpo: self,
next: self.nodes[block].child,
}
}
/// Fast, constant time dominance check with block granularity.
///
/// This computes the same result as `domtree.dominates(a, b)`, but in guaranteed fast constant
/// time. This is less general than the `DominatorTree` method because it only works with block
/// program points.
///
/// An block is considered to dominate itself.
pub fn dominates(&self, a: Block, b: Block) -> bool {
let na = &self.nodes[a];
let nb = &self.nodes[b];
na.pre_number <= nb.pre_number && na.pre_max >= nb.pre_max
}
/// Compare two blocks according to the dominator pre-order.
pub fn pre_cmp_block(&self, a: Block, b: Block) -> Ordering {
self.nodes[a].pre_number.cmp(&self.nodes[b].pre_number)
}
/// Compare two program points according to the dominator tree pre-order.
///
/// This ordering of program points have the property that given a program point, pp, all the
/// program points dominated by pp follow immediately and contiguously after pp in the order.
pub fn pre_cmp<A, B>(&self, a: A, b: B, layout: &Layout) -> Ordering
where
A: Into<ExpandedProgramPoint>,
B: Into<ExpandedProgramPoint>,
{
let a = a.into();
let b = b.into();
self.pre_cmp_block(layout.pp_block(a), layout.pp_block(b))
.then(layout.cmp(a, b))
}
/// Compare two value defs according to the dominator tree pre-order.
///
/// Two values defined at the same program point are compared according to their parameter or
/// result order.
///
/// This is a total ordering of the values in the function.
pub fn pre_cmp_def(&self, a: Value, b: Value, func: &Function) -> Ordering {
let da = func.dfg.value_def(a);
let db = func.dfg.value_def(b);
self.pre_cmp(da, db, &func.layout)
.then_with(|| da.num().cmp(&db.num()))
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::cursor::{Cursor, FuncCursor};
use crate::flowgraph::ControlFlowGraph;
use crate::ir::types::*;
use crate::ir::{Function, InstBuilder, TrapCode};
#[test]
fn empty() {
let func = Function::new();
let cfg = ControlFlowGraph::with_function(&func);
debug_assert!(cfg.is_valid());
let dtree = DominatorTree::with_function(&func, &cfg);
assert_eq!(0, dtree.nodes.keys().count());
assert_eq!(dtree.cfg_postorder(), &[]);
let mut dtpo = DominatorTreePreorder::new();
dtpo.compute(&dtree, &func.layout);
}
#[test]
fn unreachable_node() {
let mut func = Function::new();
let block0 = func.dfg.make_block();
let v0 = func.dfg.append_block_param(block0, I32);
let block1 = func.dfg.make_block();
let block2 = func.dfg.make_block();
let mut cur = FuncCursor::new(&mut func);
cur.insert_block(block0);
cur.ins().brnz(v0, block2, &[]);
cur.ins().trap(TrapCode::User(0));
cur.insert_block(block1);
let v1 = cur.ins().iconst(I32, 1);
let v2 = cur.ins().iadd(v0, v1);
cur.ins().jump(block0, &[v2]);
cur.insert_block(block2);
cur.ins().return_(&[v0]);
let cfg = ControlFlowGraph::with_function(cur.func);
let dt = DominatorTree::with_function(cur.func, &cfg);
// Fall-through-first, prune-at-source DFT:
//
// block0 {
// brnz block2 {
// trap
// block2 {
// return
// } block2
// } block0
assert_eq!(dt.cfg_postorder(), &[block2, block0]);
let v2_def = cur.func.dfg.value_def(v2).unwrap_inst();
assert!(!dt.dominates(v2_def, block0, &cur.func.layout));
assert!(!dt.dominates(block0, v2_def, &cur.func.layout));
let mut dtpo = DominatorTreePreorder::new();
dtpo.compute(&dt, &cur.func.layout);
assert!(dtpo.dominates(block0, block0));
assert!(!dtpo.dominates(block0, block1));
assert!(dtpo.dominates(block0, block2));
assert!(!dtpo.dominates(block1, block0));
assert!(dtpo.dominates(block1, block1));
assert!(!dtpo.dominates(block1, block2));
assert!(!dtpo.dominates(block2, block0));
assert!(!dtpo.dominates(block2, block1));
assert!(dtpo.dominates(block2, block2));
}
#[test]
fn non_zero_entry_block() {
let mut func = Function::new();
let block0 = func.dfg.make_block();
let block1 = func.dfg.make_block();
let block2 = func.dfg.make_block();
let block3 = func.dfg.make_block();
let cond = func.dfg.append_block_param(block3, I32);
let mut cur = FuncCursor::new(&mut func);
cur.insert_block(block3);
let jmp_block3_block1 = cur.ins().jump(block1, &[]);
cur.insert_block(block1);
let br_block1_block0 = cur.ins().brnz(cond, block0, &[]);
let jmp_block1_block2 = cur.ins().jump(block2, &[]);
cur.insert_block(block2);
cur.ins().jump(block0, &[]);
cur.insert_block(block0);
let cfg = ControlFlowGraph::with_function(cur.func);
let dt = DominatorTree::with_function(cur.func, &cfg);
// Fall-through-first, prune-at-source DFT:
//
// block3 {
// block3:jump block1 {
// block1 {
// block1:brnz block0 {
// block1:jump block2 {
// block2 {
// block2:jump block0 (seen)
// } block2
// } block1:jump block2
// block0 {
// } block0
// } block1:brnz block0
// } block1
// } block3:jump block1
// } block3
assert_eq!(dt.cfg_postorder(), &[block2, block0, block1, block3]);
assert_eq!(cur.func.layout.entry_block().unwrap(), block3);
assert_eq!(dt.idom(block3), None);
assert_eq!(dt.idom(block1).unwrap(), jmp_block3_block1);
assert_eq!(dt.idom(block2).unwrap(), jmp_block1_block2);
assert_eq!(dt.idom(block0).unwrap(), br_block1_block0);
assert!(dt.dominates(br_block1_block0, br_block1_block0, &cur.func.layout));
assert!(!dt.dominates(br_block1_block0, jmp_block3_block1, &cur.func.layout));
assert!(dt.dominates(jmp_block3_block1, br_block1_block0, &cur.func.layout));
assert_eq!(
dt.rpo_cmp(block3, block3, &cur.func.layout),
Ordering::Equal
);
assert_eq!(dt.rpo_cmp(block3, block1, &cur.func.layout), Ordering::Less);
assert_eq!(
dt.rpo_cmp(block3, jmp_block3_block1, &cur.func.layout),
Ordering::Less
);
assert_eq!(
dt.rpo_cmp(jmp_block3_block1, jmp_block1_block2, &cur.func.layout),
Ordering::Less
);
}
#[test]
fn backwards_layout() {
let mut func = Function::new();
let block0 = func.dfg.make_block();
let block1 = func.dfg.make_block();
let block2 = func.dfg.make_block();
let mut cur = FuncCursor::new(&mut func);
cur.insert_block(block0);
let jmp02 = cur.ins().jump(block2, &[]);
cur.insert_block(block1);
let trap = cur.ins().trap(TrapCode::User(5));
cur.insert_block(block2);
let jmp21 = cur.ins().jump(block1, &[]);
let cfg = ControlFlowGraph::with_function(cur.func);
let dt = DominatorTree::with_function(cur.func, &cfg);
assert_eq!(cur.func.layout.entry_block(), Some(block0));
assert_eq!(dt.idom(block0), None);
assert_eq!(dt.idom(block1), Some(jmp21));
assert_eq!(dt.idom(block2), Some(jmp02));
assert!(dt.dominates(block0, block0, &cur.func.layout));
assert!(dt.dominates(block0, jmp02, &cur.func.layout));
assert!(dt.dominates(block0, block1, &cur.func.layout));
assert!(dt.dominates(block0, trap, &cur.func.layout));
assert!(dt.dominates(block0, block2, &cur.func.layout));
assert!(dt.dominates(block0, jmp21, &cur.func.layout));
assert!(!dt.dominates(jmp02, block0, &cur.func.layout));
assert!(dt.dominates(jmp02, jmp02, &cur.func.layout));
assert!(dt.dominates(jmp02, block1, &cur.func.layout));
assert!(dt.dominates(jmp02, trap, &cur.func.layout));
assert!(dt.dominates(jmp02, block2, &cur.func.layout));
assert!(dt.dominates(jmp02, jmp21, &cur.func.layout));
assert!(!dt.dominates(block1, block0, &cur.func.layout));
assert!(!dt.dominates(block1, jmp02, &cur.func.layout));
assert!(dt.dominates(block1, block1, &cur.func.layout));
assert!(dt.dominates(block1, trap, &cur.func.layout));
assert!(!dt.dominates(block1, block2, &cur.func.layout));
assert!(!dt.dominates(block1, jmp21, &cur.func.layout));
assert!(!dt.dominates(trap, block0, &cur.func.layout));
assert!(!dt.dominates(trap, jmp02, &cur.func.layout));
assert!(!dt.dominates(trap, block1, &cur.func.layout));
assert!(dt.dominates(trap, trap, &cur.func.layout));
assert!(!dt.dominates(trap, block2, &cur.func.layout));
assert!(!dt.dominates(trap, jmp21, &cur.func.layout));
assert!(!dt.dominates(block2, block0, &cur.func.layout));
assert!(!dt.dominates(block2, jmp02, &cur.func.layout));
assert!(dt.dominates(block2, block1, &cur.func.layout));
assert!(dt.dominates(block2, trap, &cur.func.layout));
assert!(dt.dominates(block2, block2, &cur.func.layout));
assert!(dt.dominates(block2, jmp21, &cur.func.layout));
assert!(!dt.dominates(jmp21, block0, &cur.func.layout));
assert!(!dt.dominates(jmp21, jmp02, &cur.func.layout));
assert!(dt.dominates(jmp21, block1, &cur.func.layout));
assert!(dt.dominates(jmp21, trap, &cur.func.layout));
assert!(!dt.dominates(jmp21, block2, &cur.func.layout));
assert!(dt.dominates(jmp21, jmp21, &cur.func.layout));
}
}