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Rollup merge of #107662 - cjgillot:copy-projection, r=oli-obk

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Turn projections into copies in CopyProp.

The current implementation can leave behind projections that are moved out several times.

This PR widens the check to turn such moves into copies: a move out of a projection of a copy is equivalent to a copy of the original projection.
This commit is contained in:
Matthias Krüger 2023-02-07 17:57:15 +01:00 • committed by GitHub
commit 306dbaf574
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4 changed files with 69 additions and 3 deletions
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5
compiler/rustc_mir_transform/src/copy_prop.rs
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@ -153,8 +153,9 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> {
fn visit_operand(&mut self, operand: &mut Operand<'tcx>, loc: Location) {
if let Operand::Move(place) = *operand
&& let Some(local) = place.as_local()
&& !self.fully_moved.contains(local)
// A move out of a projection of a copy is equivalent to a copy of the original projection.
&& !place.has_deref()
&& !self.fully_moved.contains(place.local)
{
*operand = Operand::Copy(place);
}