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Merged
merged 2 commits into from
Feb 6, 2020
Merged

Improve merge_from_succ #68790

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0eb297d
Fix up `merge_from_succ`.
nnethercote Feb 3, 2020
d62b6f2
Pull out a special case in `merge_from_succ`.
nnethercote Feb 3, 2020
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14 changes: 11 additions & 3 deletions src/librustc_passes/liveness.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -822,8 +822,15 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
return false;
}

let mut changed = false;
let mut any_changed = false;
self.indices2(ln, succ_ln, |this, idx, succ_idx| {
// This is a special case, pulled out from the code below, where we
// don't have to do anything. It occurs about 60-70% of the time.
if this.rwu_table.packed_rwus[succ_idx] == INV_INV_FALSE {
return;
}

let mut changed = false;
let mut rwu = this.rwu_table.get(idx);
let succ_rwu = this.rwu_table.get(succ_idx);
if succ_rwu.reader.is_valid() && !rwu.reader.is_valid() {
Expand All @@ -843,6 +850,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {

if changed {
this.rwu_table.assign_unpacked(idx, rwu);
any_changed = true;
}
});

Expand All @@ -851,9 +859,9 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
ln,
self.ln_str(succ_ln),
first_merge,
changed
any_changed
);
return changed;
return any_changed;
}

// Indicates that a local variable was *defined*; we know that no
Expand Down