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Only compute is_freeze for layout-constrained ADTs

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Places are usually shallow and quick to visit. By contrast, computing
`is_freeze` can be much costlier, involving inference and trait
solving. Making sure to call `is_freeze` only when necessary should be
beneficial for performance in most cases.
This commit is contained in:
Léo Lanteri Thauvin 2021-08-03 02:00:18 +02:00
parent e3b1c12bec
commit 2b169ccc96
1 changed files with 16 additions and 18 deletions
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26
compiler/rustc_mir_build/src/check_unsafety.rs
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@ -456,27 +456,25 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
return; // we have already visited everything by now return; // we have already visited everything by now
} }
} }
ExprKind::Borrow { borrow_kind, arg } => match borrow_kind { ExprKind::Borrow { borrow_kind, arg } => {
BorrowKind::Shallow | BorrowKind::Shared | BorrowKind::Unique => { let mut visitor = LayoutConstrainedPlaceVisitor::new(self.thir, self.tcx);
visit::walk_expr(&mut visitor, expr);
if visitor.found {
match borrow_kind {
BorrowKind::Shallow | BorrowKind::Shared | BorrowKind::Unique
if !self.thir[arg] if !self.thir[arg]
.ty .ty
.is_freeze(self.tcx.at(self.thir[arg].span), self.param_env) .is_freeze(self.tcx.at(self.thir[arg].span), self.param_env) =>
{ {
let mut visitor = LayoutConstrainedPlaceVisitor::new(self.thir, self.tcx); self.requires_unsafe(expr.span, BorrowOfLayoutConstrainedField)
visit::walk_expr(&mut visitor, expr);
if visitor.found {
self.requires_unsafe(expr.span, BorrowOfLayoutConstrainedField);
}
}
} }
BorrowKind::Mut { .. } => { BorrowKind::Mut { .. } => {
let mut visitor = LayoutConstrainedPlaceVisitor::new(self.thir, self.tcx); self.requires_unsafe(expr.span, MutationOfLayoutConstrainedField)
visit::walk_expr(&mut visitor, expr); }
if visitor.found { BorrowKind::Shallow | BorrowKind::Shared | BorrowKind::Unique => {}
self.requires_unsafe(expr.span, MutationOfLayoutConstrainedField); }
} }
} }
},
_ => {} _ => {}
} }
visit::walk_expr(self, expr); visit::walk_expr(self, expr);