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Added ControlFlowGraph::recompute_ebb for incremental CFG updates.

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This commit is contained in:
Angus Holder
2017-03-12 15:20:06 +00:00
committed by Jakob Stoklund Olesen
parent 11a0daa7fd
commit 1e1a1a8797
1 changed files with 94 additions and 30 deletions
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124
lib/cretonne/src/cfg.rs
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@@ -27,6 +27,7 @@ use ir::{Function, Inst, Ebb};
use ir::instructions::BranchInfo;
use entity_map::{EntityMap, Keys};
use std::collections::HashSet;
use std::mem;
/// A basic block denoted by its enclosing Ebb and last instruction.
pub type BasicBlock = (Ebb, Inst);
@@ -74,22 +75,49 @@ impl ControlFlowGraph {
self.data.resize(func.dfg.num_ebbs());
for ebb in &func.layout {
for inst in func.layout.ebb_insts(ebb) {
match func.dfg[inst].analyze_branch(&func.dfg.value_lists) {
BranchInfo::SingleDest(dest, _) => {
self.compute_ebb(func, ebb);
}
}
fn compute_ebb(&mut self, func: &Function, ebb: Ebb) {
for inst in func.layout.ebb_insts(ebb) {
match func.dfg[inst].analyze_branch(&func.dfg.value_lists) {
BranchInfo::SingleDest(dest, _) => {
self.add_edge((ebb, inst), dest);
}
BranchInfo::Table(jt) => {
for (_, dest) in func.jump_tables[jt].entries() {
self.add_edge((ebb, inst), dest);
}
BranchInfo::Table(jt) => {
for (_, dest) in func.jump_tables[jt].entries() {
self.add_edge((ebb, inst), dest);
}
}
BranchInfo::NotABranch => {}
}
BranchInfo::NotABranch => {}
}
}
}
fn invalidate_ebb_successors(&mut self, ebb: Ebb) {
// Temporarily take ownership because we need mutable access to self.data inside the loop.
// Unfortunately borrowck cannot see that our mut accesses to predecessors don't alias
// our iteration over successors.
let mut successors = mem::replace(&mut self.data[ebb].successors, Vec::new());
for suc in successors.iter().cloned() {
self.data[suc].predecessors.retain(|&(e, _)| e != ebb);
}
successors.clear();
self.data[ebb].successors = successors;
}
/// Recompute the control flow graph of `ebb`.
///
/// This is for use after modifying instructions within a specific EBB. It recomputes all edges
/// from `ebb` while leaving edges to `ebb` intact. Its functionality a subset of that of the
/// more expensive `compute`, and should be used when we know we don't need to recompute the CFG
/// from scratch, but rather that our changes have been restricted to specific EBBs.
pub fn recompute_ebb(&mut self, func: &Function, ebb: Ebb) {
self.invalidate_ebb_successors(ebb);
self.compute_ebb(func, ebb);
}
fn add_edge(&mut self, from: BasicBlock, to: Ebb) {
self.data[from.0].successors.push(to);
self.data[to].predecessors.push(from);
@@ -207,32 +235,68 @@ mod tests {
cur.insert_ebb(ebb2);
}
let cfg = ControlFlowGraph::with_function(&func);
let mut cfg = ControlFlowGraph::with_function(&func);
let ebb0_predecessors = cfg.get_predecessors(ebb0);
let ebb1_predecessors = cfg.get_predecessors(ebb1);
let ebb2_predecessors = cfg.get_predecessors(ebb2);
{
let ebb0_predecessors = cfg.get_predecessors(ebb0);
let ebb1_predecessors = cfg.get_predecessors(ebb1);
let ebb2_predecessors = cfg.get_predecessors(ebb2);
let ebb0_successors = cfg.get_successors(ebb0);
let ebb1_successors = cfg.get_successors(ebb1);
let ebb2_successors = cfg.get_successors(ebb2);
let ebb0_successors = cfg.get_successors(ebb0);
let ebb1_successors = cfg.get_successors(ebb1);
let ebb2_successors = cfg.get_successors(ebb2);
assert_eq!(ebb0_predecessors.len(), 0);
assert_eq!(ebb1_predecessors.len(), 2);
assert_eq!(ebb2_predecessors.len(), 2);
assert_eq!(ebb0_predecessors.len(), 0);
assert_eq!(ebb1_predecessors.len(), 2);
assert_eq!(ebb2_predecessors.len(), 2);
assert_eq!(ebb1_predecessors.contains(&(ebb0, jmp_ebb0_ebb1)), true);
assert_eq!(ebb1_predecessors.contains(&(ebb1, br_ebb1_ebb1)), true);
assert_eq!(ebb2_predecessors.contains(&(ebb0, br_ebb0_ebb2)), true);
assert_eq!(ebb2_predecessors.contains(&(ebb1, jmp_ebb1_ebb2)), true);
assert_eq!(ebb1_predecessors.contains(&(ebb0, jmp_ebb0_ebb1)), true);
assert_eq!(ebb1_predecessors.contains(&(ebb1, br_ebb1_ebb1)), true);
assert_eq!(ebb2_predecessors.contains(&(ebb0, br_ebb0_ebb2)), true);
assert_eq!(ebb2_predecessors.contains(&(ebb1, jmp_ebb1_ebb2)), true);
assert_eq!(ebb0_successors.len(), 2);
assert_eq!(ebb1_successors.len(), 2);
assert_eq!(ebb2_successors.len(), 0);
assert_eq!(ebb0_successors.len(), 2);
assert_eq!(ebb1_successors.len(), 2);
assert_eq!(ebb2_successors.len(), 0);
assert_eq!(ebb0_successors.contains(&ebb1), true);
assert_eq!(ebb0_successors.contains(&ebb2), true);
assert_eq!(ebb1_successors.contains(&ebb1), true);
assert_eq!(ebb1_successors.contains(&ebb2), true);
assert_eq!(ebb0_successors.contains(&ebb1), true);
assert_eq!(ebb0_successors.contains(&ebb2), true);
assert_eq!(ebb1_successors.contains(&ebb1), true);
assert_eq!(ebb1_successors.contains(&ebb2), true);
}
// Change some instructions and recompute ebb0
func.dfg.replace(br_ebb0_ebb2).brnz(cond, ebb1, &[]);
func.dfg.replace(jmp_ebb0_ebb1).return_(&[]);
cfg.recompute_ebb(&mut func, ebb0);
let br_ebb0_ebb1 = br_ebb0_ebb2;
{
let ebb0_predecessors = cfg.get_predecessors(ebb0);
let ebb1_predecessors = cfg.get_predecessors(ebb1);
let ebb2_predecessors = cfg.get_predecessors(ebb2);
let ebb0_successors = cfg.get_successors(ebb0);
let ebb1_successors = cfg.get_successors(ebb1);
let ebb2_successors = cfg.get_successors(ebb2);
assert_eq!(ebb0_predecessors.len(), 0);
assert_eq!(ebb1_predecessors.len(), 2);
assert_eq!(ebb2_predecessors.len(), 1);
assert_eq!(ebb1_predecessors.contains(&(ebb0, br_ebb0_ebb1)), true);
assert_eq!(ebb1_predecessors.contains(&(ebb1, br_ebb1_ebb1)), true);
assert_eq!(ebb2_predecessors.contains(&(ebb0, br_ebb0_ebb2)), false);
assert_eq!(ebb2_predecessors.contains(&(ebb1, jmp_ebb1_ebb2)), true);
assert_eq!(ebb0_successors.len(), 1);
assert_eq!(ebb1_successors.len(), 2);
assert_eq!(ebb2_successors.len(), 0);
assert_eq!(ebb0_successors.contains(&ebb1), true);
assert_eq!(ebb0_successors.contains(&ebb2), false);
assert_eq!(ebb1_successors.contains(&ebb1), true);
assert_eq!(ebb1_successors.contains(&ebb2), true);
}
}
}