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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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34
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
}
}
ExprKind::Borrow { borrow_kind, arg } => match borrow_kind {
BorrowKind::Shallow | BorrowKind::Shared | BorrowKind::Unique => {
if !self.thir[arg]
.ty
.is_freeze(self.tcx.at(self.thir[arg].span), self.param_env)
{
let mut visitor = LayoutConstrainedPlaceVisitor::new(self.thir, self.tcx);
visit::walk_expr(&mut visitor, expr);
if visitor.found {
self.requires_unsafe(expr.span, BorrowOfLayoutConstrainedField);
ExprKind::Borrow { borrow_kind, arg } => {
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]
.ty
.is_freeze(self.tcx.at(self.thir[arg].span), self.param_env) =>
{
self.requires_unsafe(expr.span, BorrowOfLayoutConstrainedField)
}
BorrowKind::Mut { .. } => {
self.requires_unsafe(expr.span, MutationOfLayoutConstrainedField)
}
BorrowKind::Shallow | BorrowKind::Shared | BorrowKind::Unique => {}
}
}
BorrowKind::Mut { .. } => {
let mut visitor = LayoutConstrainedPlaceVisitor::new(self.thir, self.tcx);
visit::walk_expr(&mut visitor, expr);
if visitor.found {
self.requires_unsafe(expr.span, MutationOfLayoutConstrainedField);
}
}
},
}
_ => {}
}
visit::walk_expr(self, expr);