bjoernager/rust
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Limit storage duration of inlined always live locals

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This commit is contained in:
Tomasz Miąsko 2020-11-15 00:00:00 +00:00
parent 75042566d1
commit f27d56d1ff
7 changed files with 73 additions and 5 deletions
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39
compiler/rustc_mir/src/transform/inline.rs
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@ -459,6 +459,7 @@ impl Inliner<'tcx> {
tcx: self.tcx,
callsite_span: callsite.source_info.span,
body_span: callee_body.span,
always_live_locals: BitSet::new_filled(callee_body.local_decls.len()),
};
// Map all `Local`s, `SourceScope`s and `BasicBlock`s to new ones
@ -490,6 +491,34 @@ impl Inliner<'tcx> {
}
}
// If there are any locals without storage markers, give them storage only for the
// duration of the call.
for local in callee_body.vars_and_temps_iter() {
if integrator.always_live_locals.contains(local) {
let new_local = integrator.map_local(local);
caller_body[callsite.block].statements.push(Statement {
source_info: callsite.source_info,
kind: StatementKind::StorageLive(new_local),
});
}
}
if let Some(block) = callsite.target {
// To avoid repeated O(n) insert, push any new statements to the end and rotate
// the slice once.
let mut n = 0;
for local in callee_body.vars_and_temps_iter().rev() {
if integrator.always_live_locals.contains(local) {
let new_local = integrator.map_local(local);
caller_body[block].statements.push(Statement {
source_info: callsite.source_info,
kind: StatementKind::StorageDead(new_local),
});
n += 1;
}
}
caller_body[block].statements.rotate_right(n);
}
// Insert all of the (mapped) parts of the callee body into the caller.
caller_body.local_decls.extend(
// FIXME(eddyb) make `Range<Local>` iterable so that we can use
@ -670,6 +699,7 @@ struct Integrator<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
callsite_span: Span,
body_span: Span,
always_live_locals: BitSet<Local>,
}
impl<'a, 'tcx> Integrator<'a, 'tcx> {
@ -759,6 +789,15 @@ impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> {
}
}
fn visit_statement(&mut self, statement: &mut Statement<'tcx>, location: Location) {
if let StatementKind::StorageLive(local) | StatementKind::StorageDead(local) =
statement.kind
{
self.always_live_locals.remove(local);
}
self.super_statement(statement, location);
}
fn visit_terminator(&mut self, terminator: &mut Terminator<'tcx>, loc: Location) {
// Don't try to modify the implicit `_0` access on return (`return` terminators are
// replaced down below anyways).