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Avoid exhausting stack space in dominator compression

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This commit is contained in:
Mark Rousskov 2022-02-23 10:31:26 -05:00
parent c651ba8a54
commit 4d89292785
1 changed files with 13 additions and 3 deletions
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16
compiler/rustc_data_structures/src/graph/dominators/mod.rs
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@ -241,9 +241,19 @@ fn compress(
v: PreorderIndex,
) {
assert!(is_processed(v, lastlinked));
let u = ancestor[v];
if is_processed(u, lastlinked) {
compress(ancestor, lastlinked, semi, label, u);
// Compute the processed list of ancestors
//
// We use a heap stack here to avoid recursing too deeply, exhausting the
// stack space.
let mut stack: smallvec::SmallVec<[_; 8]> = smallvec::smallvec![v];
let mut u = ancestor[v];
while is_processed(u, lastlinked) {
stack.push(u);
u = ancestor[u];
}
// Then in reverse order, popping the stack
for &[v, u] in stack.array_windows().rev() {
if semi[label[u]] < semi[label[v]] {
label[v] = label[u];
}