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Avoid invalidating CFG caches from MirPatch::apply. #146697

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Merged
bors merged 3 commits into from
Sep 25, 2025
Merged

Avoid invalidating CFG caches from MirPatch::apply. #146697

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b216cf3
Avoid invalidating from MirPatch::apply.
cjgillot Sep 18, 2025
3c232fe
Make term_patch_map sparse.
cjgillot Sep 20, 2025
ce677c7
Update compiler/rustc_mir_transform/src/patch.rs
cjgillot Sep 23, 2025
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6 changes: 3 additions & 3 deletions compiler/rustc_mir_transform/src/patch.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -244,7 +244,7 @@ impl<'tcx> MirPatch<'tcx> {
self.new_blocks.len(),
body.basic_blocks.len()
);
let bbs = if self.term_patch_map.is_empty() && self.new_blocks.is_empty() {
let bbs = if self.term_patch_map.iter().all(Option::is_none) && self.new_blocks.is_empty() {
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@lcnr lcnr Sep 19, 2025

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so this small perf regression might be real because we're now iterating over all basic blocks here even if all are None 🤔

🤷 would still be fine with landing this, but we may also consider alternatives, e.g. I would kinda assume that the patch map will be mostly None all the time, so maybe something that's better with sparse entries would perform better here.

anyways, haven't looked much at the relevant code yet

body.basic_blocks.as_mut_preserves_cfg()
} else {
body.basic_blocks.as_mut()
Expand Down Expand Up @@ -273,8 +273,8 @@ impl<'tcx> MirPatch<'tcx> {
}
debug!("MirPatch: adding statement {:?} at loc {:?}+{}", stmt, loc, delta);
loc.statement_index += delta;
let source_info = Self::source_info_for_index(&body[loc.block], loc);
body[loc.block]
let source_info = Self::source_info_for_index(&bbs[loc.block], loc);
bbs[loc.block]
.statements
.insert(loc.statement_index, Statement::new(source_info, stmt));
delta += 1;
Expand Down
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