mikros/rust
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Don't build a map of predecessors, just count them instead

Browse Source
This commit is contained in:
James Miller 2016-03-11 19:42:26 +13:00
parent eee7f3c732
commit c70bc3a5da
1 changed files with 4 additions and 88 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

92
src/librustc_mir/transform/break_critical_edges.rs
View File

@ -7,9 +7,6 @@
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::mem;
use rustc_back::slice;
use rustc::mir::repr::*;
use rustc::mir::mir_map::MirMap;
@ -43,95 +40,14 @@ pub fn break_critical_edges<'tcx>(mir_map: &mut MirMap<'tcx>) {
}
}
/*
* Predecessor map for tracking the predecessors of a block
*/
struct PredMap {
preds: Vec<BlockPredecessors>
}
/**
* Most blocks only have one predecessor, so we can cut down on
* some allocation by not using Vec until we have more than one.
*/
#[derive(Clone)]
enum BlockPredecessors {
None,
One(BasicBlock),
Some(Vec<BasicBlock>)
}
impl PredMap {
pub fn new(n: usize) -> PredMap {
let preds = vec![BlockPredecessors::None; n];
PredMap {
preds: preds
}
}
fn ensure_len(&mut self, bb: BasicBlock) {
let idx = bb.index();
while self.preds.len() <= idx {
self.preds.push(BlockPredecessors::None);
}
}
pub fn add_pred(&mut self, target: BasicBlock, pred: BasicBlock) {
self.ensure_len(target);
let preds = mem::replace(&mut self.preds[target.index()], BlockPredecessors::None);
match preds {
BlockPredecessors::None => {
self.preds[target.index()] = BlockPredecessors::One(pred);
}
BlockPredecessors::One(bb) => {
self.preds[target.index()] = BlockPredecessors::Some(vec![bb, pred]);
}
BlockPredecessors::Some(mut preds) => {
preds.push(pred);
self.preds[target.index()] = BlockPredecessors::Some(preds);
}
}
}
pub fn remove_pred(&mut self, target: BasicBlock, pred: BasicBlock) {
self.ensure_len(target);
let preds = mem::replace(&mut self.preds[target.index()], BlockPredecessors::None);
match preds {
BlockPredecessors::None => {}
BlockPredecessors::One(bb) if bb == pred => {}
BlockPredecessors::One(bb) => {
self.preds[target.index()] = BlockPredecessors::One(bb);
}
BlockPredecessors::Some(mut preds) => {
preds.retain(|&bb| bb != pred);
self.preds[target.index()] = BlockPredecessors::Some(preds);
}
}
}
pub fn get_preds(&self, bb: BasicBlock) -> &[BasicBlock] {
match self.preds[bb.index()] {
BlockPredecessors::None => &[],
BlockPredecessors::One(ref bb) => slice::ref_slice(bb),
BlockPredecessors::Some(ref bbs) => &bbs[..]
}
}
}
fn break_critical_edges_fn(mir: &mut Mir) {
let mut pred_map = PredMap::new(mir.basic_blocks.len());
let mut pred_count = vec![0u32; mir.basic_blocks.len()];
// Build the precedecessor map for the MIR
for (pred, data) in traversal::preorder(mir) {
for (_, data) in traversal::preorder(mir) {
if let Some(ref term) = data.terminator {
for &tgt in term.successors().iter() {
pred_map.add_pred(tgt, pred);
pred_count[tgt.index()] += 1;
}
}
}
@ -150,7 +66,7 @@ fn break_critical_edges_fn(mir: &mut Mir) {
let succs = term.successors_mut();
if succs.len() > 1 || (succs.len() > 0 && is_invoke) {
for tgt in succs {
let num_preds = pred_map.get_preds(*tgt).len();
let num_preds = pred_count[tgt.index()];
if num_preds > 1 {
// It's a critical edge, break it
let goto = Terminator::Goto { target: *tgt };