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use crate::{analysis::DominatorTree, ir::prelude::*, opt::prelude::*};
use std::collections::{HashMap, HashSet};
pub struct EarlyCodeMotion;
impl Pass for EarlyCodeMotion {
fn run_on_cfg(ctx: &PassContext, unit: &mut UnitBuilder) -> bool {
info!("ECM [{}]", unit.name());
let mut modified = false;
let pred = unit.predtbl();
let dt = unit.domtree_with_predtbl(&pred);
let mut block_numbers = HashMap::<Block, usize>::new();
let mut work_done = HashSet::<Block>::new();
let mut work_pending = HashSet::<Block>::new();
let entry = unit.entry();
work_pending.insert(entry);
block_numbers.insert(entry, 0);
while let Some(&block) = work_pending.iter().next() {
work_pending.remove(&block);
work_done.insert(block);
trace!("Working on {}", block.dump(&unit));
for inst in unit.insts(block).collect::<Vec<_>>() {
modified |= move_instruction(ctx, unit, block, inst, &dt, &block_numbers);
}
let term = unit.terminator(block);
if unit[term].opcode().is_terminator() {
work_pending.extend(
unit[term]
.blocks()
.iter()
.cloned()
.filter(|bb| !work_done.contains(bb)),
);
let next_number = block_numbers[&block] + 1;
for bb in unit[term].blocks().iter().cloned() {
block_numbers.entry(bb).or_insert(next_number);
}
}
}
trace!("Final block numbers:");
for (bb, num) in block_numbers {
trace!(" {} = {}", bb.dump(&unit), num);
}
modified
}
}
fn move_instruction(
_ctx: &PassContext,
unit: &mut UnitBuilder,
block: Block,
inst: Inst,
dt: &DominatorTree,
block_numbers: &HashMap<Block, usize>,
) -> bool {
let op = unit[inst].opcode();
if op == Opcode::Ld
|| op == Opcode::St
|| op == Opcode::Prb
|| op == Opcode::Drv
|| op == Opcode::Phi
|| op.is_terminator()
{
return false;
}
trace!(" Working on {}", inst.dump(&unit));
let doms: Vec<_> = unit[inst]
.args()
.iter()
.flat_map(|&arg| unit.get_value_inst(arg))
.map(|inst| unit.inst_block(inst).unwrap())
.map(|block| dt.dominated_by(block))
.collect();
if doms.is_empty() {
let entry = unit.entry();
let entry_term = unit.terminator(entry);
if unit.inst_block(inst) == Some(entry) {
return false;
}
unit.remove_inst(inst);
unit.insert_inst_before(inst, entry_term);
debug!("Move {} into {}", inst.dump(&unit), entry.dump(&unit));
return true;
}
let possible_bbs = doms
.get(0)
.into_iter()
.flat_map(|bbs| bbs.iter())
.filter(|bb| doms.iter().all(|bbs| bbs.contains(bb)))
.cloned();
let best_bb = possible_bbs
.flat_map(|bb| block_numbers.get(&bb).map(|&num| (bb, num)))
.min_by_key(|&(_, num)| num)
.map(|(bb, _)| bb);
let best_bb = match best_bb {
Some(bb) => bb,
None => return false,
};
trace!(" Best block: {}", best_bb.dump(&unit));
if best_bb == block {
return false;
}
debug!("Move {} into {}", inst.dump(&unit), best_bb.dump(&unit));
let term = unit.terminator(best_bb);
unit.remove_inst(inst);
unit.insert_inst_before(inst, term);
true
}