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Exclude locals completely, instead of individual places

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This commit is contained in:
Jannis Christopher Köhl 2022-11-12 14:57:14 +01:00
parent b3f648958d
commit 2e034dc68c
3 changed files with 85 additions and 29 deletions
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47
compiler/rustc_mir_dataflow/src/value_analysis.rs
View file

@ -34,7 +34,7 @@
use std::fmt::{Debug, Formatter};
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::fx::FxHashMap;
use rustc_index::vec::IndexVec;
use rustc_middle::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
use rustc_middle::mir::*;
@ -587,7 +587,8 @@ impl Map {
filter: impl FnMut(Ty<'tcx>) -> bool,
) -> Self {
let mut map = Self::new();
map.register_with_filter(tcx, body, filter, &escaped_places(body));
let exclude = excluded_locals(body);
map.register_with_filter(tcx, body, filter, &exclude);
debug!("registered {} places ({} nodes in total)", map.value_count, map.places.len());
map
}
@ -598,19 +599,14 @@ impl Map {
tcx: TyCtxt<'tcx>,
body: &Body<'tcx>,
mut filter: impl FnMut(Ty<'tcx>) -> bool,
exclude: &FxHashSet<Place<'tcx>>,
exclude: &IndexVec<Local, bool>,
) {
// We use this vector as stack, pushing and popping projections.
let mut projection = Vec::new();
for (local, decl) in body.local_decls.iter_enumerated() {
self.register_with_filter_rec(
tcx,
local,
&mut projection,
decl.ty,
&mut filter,
exclude,
);
if !exclude[local] {
self.register_with_filter_rec(tcx, local, &mut projection, decl.ty, &mut filter);
}
}
}
@ -624,17 +620,10 @@ impl Map {
projection: &mut Vec<PlaceElem<'tcx>>,
ty: Ty<'tcx>,
filter: &mut impl FnMut(Ty<'tcx>) -> bool,
exclude: &FxHashSet<Place<'tcx>>,
) {
let place = Place { local, projection: tcx.intern_place_elems(projection) };
if exclude.contains(&place) {
// This will also exclude all projections of the excluded place.
return;
}
// Note: The framework supports only scalars for now.
if filter(ty) && ty.is_scalar() {
trace!("registering place: {:?}", place);
// trace!("registering place {:?}", PlaceRef { local, projection: &*projection });
// We know that the projection only contains trackable elements.
let place = self.make_place(local, projection).unwrap();
@ -653,7 +642,7 @@ impl Map {
return;
}
projection.push(PlaceElem::Field(field, ty));
self.register_with_filter_rec(tcx, local, projection, ty, filter, exclude);
self.register_with_filter_rec(tcx, local, projection, ty, filter);
projection.pop();
});
}
@ -835,27 +824,27 @@ fn iter_fields<'tcx>(
}
}
/// Returns all places, that have their reference or address taken.
///
/// This includes shared references, and also drops and `InlineAsm` out parameters.
fn escaped_places<'tcx>(body: &Body<'tcx>) -> FxHashSet<Place<'tcx>> {
struct Collector<'tcx> {
result: FxHashSet<Place<'tcx>>,
/// Returns all locals with projections that have their reference or address taken.
fn excluded_locals<'tcx>(body: &Body<'tcx>) -> IndexVec<Local, bool> {
struct Collector {
result: IndexVec<Local, bool>,
}
impl<'tcx> Visitor<'tcx> for Collector<'tcx> {
impl<'tcx> Visitor<'tcx> for Collector {
fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
if context.is_borrow()
|| context.is_address_of()
|| context.is_drop()
|| context == PlaceContext::MutatingUse(MutatingUseContext::AsmOutput)
{
self.result.insert(*place);
// A pointer to a place could be used to access other places with the same local,
// hence we have to exclude the local completely.
self.result[place.local] = true;
}
}
}
let mut collector = Collector { result: FxHashSet::default() };
let mut collector = Collector { result: IndexVec::from_elem(false, &body.local_decls) };
collector.visit_body(body);
collector.result
}

56
src/test/mir-opt/dataflow-const-prop/sibling_ptr.main.DataflowConstProp.diff Normal file
View file

@ -0,0 +1,56 @@
- // MIR for `main` before DataflowConstProp
+ // MIR for `main` after DataflowConstProp
fn main() -> () {
let mut _0: (); // return place in scope 0 at $DIR/sibling_ptr.rs:+0:11: +0:11
let mut _1: (u8, u8); // in scope 0 at $DIR/sibling_ptr.rs:+1:9: +1:14
let _2: (); // in scope 0 at $DIR/sibling_ptr.rs:+2:5: +5:6
let mut _4: *mut u8; // in scope 0 at $DIR/sibling_ptr.rs:+4:10: +4:18
let mut _5: *mut u8; // in scope 0 at $DIR/sibling_ptr.rs:+4:10: +4:11
scope 1 {
debug x => _1; // in scope 1 at $DIR/sibling_ptr.rs:+1:9: +1:14
let _6: u8; // in scope 1 at $DIR/sibling_ptr.rs:+6:9: +6:11
scope 2 {
let _3: *mut u8; // in scope 2 at $DIR/sibling_ptr.rs:+3:13: +3:14
scope 3 {
debug p => _3; // in scope 3 at $DIR/sibling_ptr.rs:+3:13: +3:14
}
}
scope 4 {
debug x1 => _6; // in scope 4 at $DIR/sibling_ptr.rs:+6:9: +6:11
}
}
bb0: {
StorageLive(_1); // scope 0 at $DIR/sibling_ptr.rs:+1:9: +1:14
Deinit(_1); // scope 0 at $DIR/sibling_ptr.rs:+1:27: +1:33
(_1.0: u8) = const 0_u8; // scope 0 at $DIR/sibling_ptr.rs:+1:27: +1:33
(_1.1: u8) = const 0_u8; // scope 0 at $DIR/sibling_ptr.rs:+1:27: +1:33
StorageLive(_2); // scope 1 at $DIR/sibling_ptr.rs:+2:5: +5:6
StorageLive(_3); // scope 2 at $DIR/sibling_ptr.rs:+3:13: +3:14
_3 = &raw mut (_1.0: u8); // scope 2 at $SRC_DIR/core/src/ptr/mod.rs:LL:COL
StorageLive(_4); // scope 3 at $DIR/sibling_ptr.rs:+4:10: +4:18
StorageLive(_5); // scope 3 at $DIR/sibling_ptr.rs:+4:10: +4:11
_5 = _3; // scope 3 at $DIR/sibling_ptr.rs:+4:10: +4:11
_4 = ptr::mut_ptr::<impl *mut u8>::add(move _5, const 1_usize) -> bb1; // scope 3 at $DIR/sibling_ptr.rs:+4:10: +4:18
// mir::Constant
// + span: $DIR/sibling_ptr.rs:8:12: 8:15
// + literal: Const { ty: unsafe fn(*mut u8, usize) -> *mut u8 {ptr::mut_ptr::<impl *mut u8>::add}, val: Value(<ZST>) }
}
bb1: {
StorageDead(_5); // scope 3 at $DIR/sibling_ptr.rs:+4:17: +4:18
(*_4) = const 1_u8; // scope 3 at $DIR/sibling_ptr.rs:+4:9: +4:22
StorageDead(_4); // scope 3 at $DIR/sibling_ptr.rs:+4:22: +4:23
_2 = const (); // scope 2 at $DIR/sibling_ptr.rs:+2:5: +5:6
StorageDead(_3); // scope 2 at $DIR/sibling_ptr.rs:+5:5: +5:6
StorageDead(_2); // scope 1 at $DIR/sibling_ptr.rs:+5:5: +5:6
StorageLive(_6); // scope 1 at $DIR/sibling_ptr.rs:+6:9: +6:11
_6 = (_1.1: u8); // scope 1 at $DIR/sibling_ptr.rs:+6:14: +6:17
_0 = const (); // scope 0 at $DIR/sibling_ptr.rs:+0:11: +7:2
StorageDead(_6); // scope 1 at $DIR/sibling_ptr.rs:+7:1: +7:2
StorageDead(_1); // scope 0 at $DIR/sibling_ptr.rs:+7:1: +7:2
return; // scope 0 at $DIR/sibling_ptr.rs:+7:2: +7:2
}
}

11
src/test/mir-opt/dataflow-const-prop/sibling_ptr.rs Normal file
View file

@ -0,0 +1,11 @@
// unit-test: DataflowConstProp
// EMIT_MIR sibling_ptr.main.DataflowConstProp.diff
fn main() {
let mut x: (u8, u8) = (0, 0);
unsafe {
let p = std::ptr::addr_of_mut!(x.0);
*p.add(1) = 1;
}
let x1 = x.1; // should not be propagated
}