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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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4
compiler/rustc_middle/src/mir/mod.rs
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@ -420,7 +420,9 @@ pub fn args_iter(&self) -> impl Iterator<Item = Local> + ExactSizeIterator {
/// Returns an iterator over all user-defined variables and compiler-generated temporaries (all
/// locals that are neither arguments nor the return place).
#[inline]
pub fn vars_and_temps_iter(&self) -> impl Iterator<Item = Local> + ExactSizeIterator {
pub fn vars_and_temps_iter(
&self,
) -> impl DoubleEndedIterator<Item = Local> + ExactSizeIterator {
let arg_count = self.arg_count;
let local_count = self.local_decls.len();
(arg_count + 1..local_count).map(Local::new)

39
compiler/rustc_mir/src/transform/inline.rs
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@ -459,6 +459,7 @@ fn dest_needs_borrow(place: Place<'_>) -> bool {
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 @@ fn dest_needs_borrow(place: Place<'_>) -> bool {
}
}
// 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 @@ fn visit_retag(&mut self, kind: &mut RetagKind, place: &mut Place<'tcx>, loc: Lo
}
}
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).

1
src/test/mir-opt/inline/inline_diverging.h.Inline.diff
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@ -40,6 +40,7 @@
- // mir::Constant
// + span: $DIR/inline-diverging.rs:22:16: 22:21
// + literal: Const { ty: fn() -> ! {sleep}, val: Value(Scalar(<ZST>)) }
+ StorageLive(_6); // scope 0 at $DIR/inline-diverging.rs:22:5: 22:22
+ StorageLive(_3); // scope 1 at $DIR/inline-diverging.rs:22:5: 22:22
+ StorageLive(_4); // scope 1 at $DIR/inline-diverging.rs:22:5: 22:22
+ _4 = &_2; // scope 1 at $DIR/inline-diverging.rs:22:5: 22:22

4
src/test/mir-opt/inline/inline_generator.main.Inline.diff
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@ -65,12 +65,16 @@
- // + literal: Const { ty: for<'r> fn(std::pin::Pin<&'r mut impl std::ops::Generator<bool>>, bool) -> std::ops::GeneratorState<<impl std::ops::Generator<bool> as std::ops::Generator<bool>>::Yield, <impl std::ops::Generator<bool> as std::ops::Generator<bool>>::Return> {<impl std::ops::Generator<bool> as std::ops::Generator<bool>>::resume}, val: Value(Scalar(<ZST>)) }
+ StorageLive(_7); // scope 0 at $DIR/inline-generator.rs:9:14: 9:46
+ _7 = const false; // scope 0 at $DIR/inline-generator.rs:9:14: 9:46
+ StorageLive(_8); // scope 0 at $DIR/inline-generator.rs:9:14: 9:46
+ StorageLive(_9); // scope 0 at $DIR/inline-generator.rs:9:14: 9:46
+ _9 = discriminant((*(_2.0: &mut [generator@$DIR/inline-generator.rs:15:5: 15:41 {bool, i32}]))); // scope 6 at $DIR/inline-generator.rs:9:14: 9:46
+ switchInt(move _9) -> [0_u32: bb3, 1_u32: bb8, 3_u32: bb7, otherwise: bb9]; // scope 6 at $DIR/inline-generator.rs:9:14: 9:46
}
- bb3: {
+ bb1: {
+ StorageDead(_9); // scope 0 at $DIR/inline-generator.rs:9:14: 9:46
+ StorageDead(_8); // scope 0 at $DIR/inline-generator.rs:9:14: 9:46
+ StorageDead(_7); // scope 0 at $DIR/inline-generator.rs:9:14: 9:46
StorageDead(_2); // scope 0 at $DIR/inline-generator.rs:9:45: 9:46
StorageDead(_4); // scope 0 at $DIR/inline-generator.rs:9:46: 9:47

4
src/test/mir-opt/inline/inline_shims.drop.Inline.diff
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@ -36,11 +36,15 @@
- // mir::Constant
- // + span: $DIR/inline-shims.rs:12:14: 12:37
- // + literal: Const { ty: unsafe fn(*mut std::option::Option<B>) {std::intrinsics::drop_in_place::<std::option::Option<B>>}, val: Value(Scalar(<ZST>)) }
+ StorageLive(_6); // scope 2 at $DIR/inline-shims.rs:12:14: 12:40
+ StorageLive(_7); // scope 2 at $DIR/inline-shims.rs:12:14: 12:40
+ _6 = discriminant((*_5)); // scope 3 at $DIR/inline-shims.rs:12:14: 12:40
+ switchInt(move _6) -> [0_isize: bb2, otherwise: bb3]; // scope 3 at $DIR/inline-shims.rs:12:14: 12:40
}
bb2: {
+ StorageDead(_7); // scope 2 at $DIR/inline-shims.rs:12:14: 12:40
+ StorageDead(_6); // scope 2 at $DIR/inline-shims.rs:12:14: 12:40
StorageDead(_5); // scope 2 at $DIR/inline-shims.rs:12:39: 12:40
return; // scope 0 at $DIR/inline-shims.rs:13:2: 13:2
+ }

10
src/test/ui/mir/auxiliary/issue_76375_aux.rs
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@ -1,8 +1,8 @@
// edition:2018
// compile-flags: -Z mir-opt-level=2 -Z unsound-mir-opts
// compile-flags: -Z mir-opt-level=2
#[inline(always)]
pub fn f(s: bool) -> String {
pub fn copy_prop(s: bool) -> String {
let a = "Hello world!".to_string();
let b = a;
let c = b;
@ -12,3 +12,9 @@ pub fn f(s: bool) -> String {
String::new()
}
}
#[inline(always)]
pub fn dest_prop(x: &[u8]) -> &[u8] {
let y = &x[..x.len()];
y
}

16
src/test/ui/mir/issue-76375.rs
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@ -1,6 +1,8 @@
// Regression test for issue #76375.
//
// edition:2018
// build-pass
// compile-flags: -Z mir-opt-level=2 -L.
// compile-flags: -Z mir-opt-level=2
// aux-build:issue_76375_aux.rs
#![crate_type = "lib"]
@ -8,8 +10,18 @@
extern crate issue_76375_aux;
pub async fn g() {
issue_76375_aux::f(true);
issue_76375_aux::copy_prop(true);
h().await;
}
pub async fn u() {
let b = [0u8; 32];
let mut i = 0;
while i != 10 {
issue_76375_aux::dest_prop(&b);
h().await;
i += 1;
}
}
pub async fn h() {}