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Fix fuzzbug

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This commit is contained in:
Chris Fallin 2021-12-15 19:02:14 -08:00
parent e63bb7a113
commit ba80cea24b
1 changed files with 15 additions and 39 deletions
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54
src/backend/stackify.rs
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@ -281,13 +281,22 @@ impl Shape {
// those loops.
let start_loopnest = &loop_nest[start];
let end_loopnest = &loop_nest[block];
let extra_loops = start_loopnest
.strip_prefix(&end_loopnest[..])
.expect("Irreducible control flow");
let start = if extra_loops.len() > 0 {
extra_loops[0].0
// Find common prefix of loopnests at start and end
// points, and put a block start at the top of that
// loop. In other words, we put the block around the
// innermost loop that surrounds the whole forward
// edge (or around the whole body if not). As long as
// control flow is reducible, this will not result in
// an edge into a loop.
let start_idx = start_loopnest
.iter()
.zip(end_loopnest.iter())
.take_while(|(a, b)| a == b)
.count();
let start = if start_idx > 0 {
start_loopnest[start_idx - 1].0
} else {
start
0
};
block_starts[start].push(block);
@ -309,39 +318,6 @@ impl Shape {
}
}
// Fix up contiguous runs of `Forward` regions: when we have
// overlap, make them properly nest. We need to scan backward
// to do this.
log::trace!("before forward-edge re-nesting: {:?}", regions);
let mut stack: Vec<usize> = vec![];
for i in (0..regions.len()).rev() {
if !regions[i].is_forward() {
continue;
}
log::trace!("cleaning up forward edges: looking at {:?}", regions[i]);
while let Some(&top_idx) = stack.last() {
if regions[i].end() <= regions[top_idx].start() {
stack.pop();
} else {
break;
}
}
stack.push(i);
for &stack_idx in &stack {
log::trace!(" -> examining against {:?}", regions[stack_idx]);
if regions[i].start() < regions[stack_idx].start() {
let inner =
Region::Forward(regions[i].start().block, regions[stack_idx].end().block);
let outer = Region::Forward(regions[i].start().block, regions[i].end().block);
regions[stack_idx] = outer;
regions[i] = inner;
log::trace!(" -> re-nest");
}
}
}
log::trace!("after stackifying: {:?}", regions);
// Ensure the regions properly nest.