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Only assume Stacked Borrows if -Zunsound-mir-opts is given

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This commit is contained in:
Jannis Christopher Köhl 2022-10-07 01:10:10 +02:00
parent 111324e17c
commit 3c0f3b04b5
7 changed files with 137 additions and 86 deletions
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9
compiler/rustc_middle/src/mir/visit.rs
View file

@ -1320,6 +1320,15 @@ impl PlaceContext {
) )
} }
/// Returns `true` if this place context represents an address-of.
pub fn is_address_of(&self) -> bool {
matches!(
self,
PlaceContext::NonMutatingUse(NonMutatingUseContext::AddressOf)
| PlaceContext::MutatingUse(MutatingUseContext::AddressOf)
)
}
/// Returns `true` if this place context represents a storage live or storage dead marker. /// Returns `true` if this place context represents a storage live or storage dead marker.
#[inline] #[inline]
pub fn is_storage_marker(&self) -> bool { pub fn is_storage_marker(&self) -> bool {

44
compiler/rustc_mir_dataflow/src/value_analysis.rs
View file

@ -70,6 +70,7 @@ use std::fmt::{Debug, Formatter};
use rustc_data_structures::fx::FxHashMap; use rustc_data_structures::fx::FxHashMap;
use rustc_index::vec::IndexVec; use rustc_index::vec::IndexVec;
use rustc_middle::mir::tcx::PlaceTy; use rustc_middle::mir::tcx::PlaceTy;
use rustc_middle::mir::visit::{PlaceContext, Visitor};
use rustc_middle::mir::*; use rustc_middle::mir::*;
use rustc_middle::ty::{self, Ty, TyCtxt}; use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::DUMMY_SP; use rustc_span::DUMMY_SP;
@ -567,7 +568,17 @@ impl Map {
filter: impl FnMut(Ty<'tcx>) -> bool, filter: impl FnMut(Ty<'tcx>) -> bool,
) -> Self { ) -> Self {
let mut map = Self::new(); let mut map = Self::new();
map.register_with_filter(tcx, body, 3, filter);
// If `-Zunsound-mir-opts` is given, tracking through references, and tracking of places
// that have their reference taken is allowed. This would be "unsound" in the sense that
// the correctness relies on an aliasing model similar to Stacked Borrows (which is
// not yet guaranteed).
if tcx.sess.opts.unstable_opts.unsound_mir_opts {
map.register_with_filter(tcx, body, 3, filter, &[]);
} else {
map.register_with_filter(tcx, body, 0, filter, &escaped_places(body));
}
map map
} }
@ -577,6 +588,7 @@ impl Map {
body: &Body<'tcx>, body: &Body<'tcx>,
max_derefs: u32, max_derefs: u32,
mut filter: impl FnMut(Ty<'tcx>) -> bool, mut filter: impl FnMut(Ty<'tcx>) -> bool,
exclude: &[Place<'tcx>],
) { ) {
let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id()); let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id());
let mut projection = Vec::new(); let mut projection = Vec::new();
@ -589,6 +601,7 @@ impl Map {
decl.ty, decl.ty,
&mut filter, &mut filter,
param_env, param_env,
exclude,
); );
} }
} }
@ -602,11 +615,18 @@ impl Map {
ty: Ty<'tcx>, ty: Ty<'tcx>,
filter: &mut impl FnMut(Ty<'tcx>) -> bool, filter: &mut impl FnMut(Ty<'tcx>) -> bool,
param_env: ty::ParamEnv<'tcx>, param_env: ty::ParamEnv<'tcx>,
exclude: &[Place<'tcx>],
) { ) {
// This check could be improved.
if exclude.contains(&Place { local, projection: tcx.intern_place_elems(projection) }) {
return;
}
if filter(ty) { if filter(ty) {
// This might fail if `ty` is not scalar. // This might fail if `ty` is not scalar.
let _ = self.register_with_ty(local, projection, ty); let _ = self.register_with_ty(local, projection, ty);
} }
if max_derefs > 0 { if max_derefs > 0 {
if let Some(ty::TypeAndMut { ty: deref_ty, .. }) = ty.builtin_deref(false) { if let Some(ty::TypeAndMut { ty: deref_ty, .. }) = ty.builtin_deref(false) {
// References can only be tracked if the target is `!Freeze`. // References can only be tracked if the target is `!Freeze`.
@ -620,6 +640,7 @@ impl Map {
deref_ty, deref_ty,
filter, filter,
param_env, param_env,
exclude,
); );
projection.pop(); projection.pop();
} }
@ -632,7 +653,7 @@ impl Map {
} }
projection.push(PlaceElem::Field(field, ty)); projection.push(PlaceElem::Field(field, ty));
self.register_with_filter_rec( self.register_with_filter_rec(
tcx, max_derefs, local, projection, ty, filter, param_env, tcx, max_derefs, local, projection, ty, filter, param_env, exclude,
); );
projection.pop(); projection.pop();
}); });
@ -751,6 +772,25 @@ impl PlaceInfo {
} }
} }
/// Returns all places, that have their reference or address taken.
fn escaped_places<'tcx>(body: &Body<'tcx>) -> Vec<Place<'tcx>> {
struct Collector<'tcx> {
result: Vec<Place<'tcx>>,
}
impl<'tcx> Visitor<'tcx> for Collector<'tcx> {
fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
if context.is_borrow() || context.is_address_of() {
self.result.push(*place);
}
}
}
let mut collector = Collector { result: Vec::new() };
collector.visit_body(body);
collector.result
}
struct Children<'a> { struct Children<'a> {
map: &'a Map, map: &'a Map,
next: Option<PlaceIndex>, next: Option<PlaceIndex>,

1
src/test/mir-opt/dataflow-const-prop/cast.rs
View file

@ -1,4 +1,5 @@
// unit-test: DataflowConstProp // unit-test: DataflowConstProp
// compile-flags: -Zunsound-mir-opts
// EMIT_MIR cast.main.DataflowConstProp.diff // EMIT_MIR cast.main.DataflowConstProp.diff
fn main() { fn main() {

164
src/test/mir-opt/dataflow-const-prop/if.main.DataflowConstProp.diff
View file

@ -3,30 +3,30 @@
fn main() -> () { fn main() -> () {
let mut _0: (); // return place in scope 0 at $DIR/if.rs:+0:11: +0:11 let mut _0: (); // return place in scope 0 at $DIR/if.rs:+0:11: +0:11
let _1: i32; // in scope 0 at $DIR/if.rs:+2:9: +2:10 let _1: i32; // in scope 0 at $DIR/if.rs:+1:9: +1:10
let mut _3: bool; // in scope 0 at $DIR/if.rs:+3:16: +3:24 let mut _3: bool; // in scope 0 at $DIR/if.rs:+2:16: +2:24
let mut _4: i32; // in scope 0 at $DIR/if.rs:+3:16: +3:19 let mut _4: i32; // in scope 0 at $DIR/if.rs:+2:16: +2:19
let mut _5: &i32; // in scope 0 at $DIR/if.rs:+3:17: +3:19 let mut _5: &i32; // in scope 0 at $DIR/if.rs:+2:17: +2:19
let mut _7: i32; // in scope 0 at $DIR/if.rs:+4:13: +4:14 let mut _7: i32; // in scope 0 at $DIR/if.rs:+3:13: +3:14
let mut _9: bool; // in scope 0 at $DIR/if.rs:+6:16: +6:24 let mut _9: bool; // in scope 0 at $DIR/if.rs:+5:16: +5:24
let mut _10: i32; // in scope 0 at $DIR/if.rs:+6:16: +6:19 let mut _10: i32; // in scope 0 at $DIR/if.rs:+5:16: +5:19
let mut _11: &i32; // in scope 0 at $DIR/if.rs:+6:17: +6:19 let mut _11: &i32; // in scope 0 at $DIR/if.rs:+5:17: +5:19
let mut _12: i32; // in scope 0 at $DIR/if.rs:+6:38: +6:39 let mut _12: i32; // in scope 0 at $DIR/if.rs:+5:38: +5:39
let mut _14: i32; // in scope 0 at $DIR/if.rs:+7:13: +7:14 let mut _14: i32; // in scope 0 at $DIR/if.rs:+6:13: +6:14
scope 1 { scope 1 {
debug a => _1; // in scope 1 at $DIR/if.rs:+2:9: +2:10 debug a => _1; // in scope 1 at $DIR/if.rs:+1:9: +1:10
let _2: i32; // in scope 1 at $DIR/if.rs:+3:9: +3:10 let _2: i32; // in scope 1 at $DIR/if.rs:+2:9: +2:10
scope 2 { scope 2 {
debug b => _2; // in scope 2 at $DIR/if.rs:+3:9: +3:10 debug b => _2; // in scope 2 at $DIR/if.rs:+2:9: +2:10
let _6: i32; // in scope 2 at $DIR/if.rs:+4:9: +4:10 let _6: i32; // in scope 2 at $DIR/if.rs:+3:9: +3:10
scope 3 { scope 3 {
debug c => _6; // in scope 3 at $DIR/if.rs:+4:9: +4:10 debug c => _6; // in scope 3 at $DIR/if.rs:+3:9: +3:10
let _8: i32; // in scope 3 at $DIR/if.rs:+6:9: +6:10 let _8: i32; // in scope 3 at $DIR/if.rs:+5:9: +5:10
scope 4 { scope 4 {
debug d => _8; // in scope 4 at $DIR/if.rs:+6:9: +6:10 debug d => _8; // in scope 4 at $DIR/if.rs:+5:9: +5:10
let _13: i32; // in scope 4 at $DIR/if.rs:+7:9: +7:10 let _13: i32; // in scope 4 at $DIR/if.rs:+6:9: +6:10
scope 5 { scope 5 {
debug e => _13; // in scope 5 at $DIR/if.rs:+7:9: +7:10 debug e => _13; // in scope 5 at $DIR/if.rs:+6:9: +6:10
} }
} }
} }
@ -34,87 +34,87 @@
} }
bb0: { bb0: {
StorageLive(_1); // scope 0 at $DIR/if.rs:+2:9: +2:10 StorageLive(_1); // scope 0 at $DIR/if.rs:+1:9: +1:10
_1 = const 1_i32; // scope 0 at $DIR/if.rs:+2:13: +2:14 _1 = const 1_i32; // scope 0 at $DIR/if.rs:+1:13: +1:14
StorageLive(_2); // scope 1 at $DIR/if.rs:+3:9: +3:10 StorageLive(_2); // scope 1 at $DIR/if.rs:+2:9: +2:10
StorageLive(_3); // scope 1 at $DIR/if.rs:+3:16: +3:24 StorageLive(_3); // scope 1 at $DIR/if.rs:+2:16: +2:24
StorageLive(_4); // scope 1 at $DIR/if.rs:+3:16: +3:19 StorageLive(_4); // scope 1 at $DIR/if.rs:+2:16: +2:19
StorageLive(_5); // scope 1 at $DIR/if.rs:+3:17: +3:19 StorageLive(_5); // scope 1 at $DIR/if.rs:+2:17: +2:19
_5 = &_1; // scope 1 at $DIR/if.rs:+3:17: +3:19 _5 = &_1; // scope 1 at $DIR/if.rs:+2:17: +2:19
- _4 = (*_5); // scope 1 at $DIR/if.rs:+3:16: +3:19 - _4 = (*_5); // scope 1 at $DIR/if.rs:+2:16: +2:19
- _3 = Eq(move _4, const 1_i32); // scope 1 at $DIR/if.rs:+3:16: +3:24 - _3 = Eq(move _4, const 1_i32); // scope 1 at $DIR/if.rs:+2:16: +2:24
+ _4 = const 1_i32; // scope 1 at $DIR/if.rs:+3:16: +3:19 + _4 = const 1_i32; // scope 1 at $DIR/if.rs:+2:16: +2:19
+ _3 = const true; // scope 1 at $DIR/if.rs:+3:16: +3:24 + _3 = const true; // scope 1 at $DIR/if.rs:+2:16: +2:24
StorageDead(_5); // scope 1 at $DIR/if.rs:+3:23: +3:24 StorageDead(_5); // scope 1 at $DIR/if.rs:+2:23: +2:24
StorageDead(_4); // scope 1 at $DIR/if.rs:+3:23: +3:24 StorageDead(_4); // scope 1 at $DIR/if.rs:+2:23: +2:24
- switchInt(move _3) -> [false: bb2, otherwise: bb1]; // scope 1 at $DIR/if.rs:+3:16: +3:24 - switchInt(move _3) -> [false: bb2, otherwise: bb1]; // scope 1 at $DIR/if.rs:+2:16: +2:24
+ switchInt(const true) -> [false: bb2, otherwise: bb1]; // scope 1 at $DIR/if.rs:+3:16: +3:24 + switchInt(const true) -> [false: bb2, otherwise: bb1]; // scope 1 at $DIR/if.rs:+2:16: +2:24
} }
bb1: { bb1: {
_2 = const 2_i32; // scope 1 at $DIR/if.rs:+3:27: +3:28 _2 = const 2_i32; // scope 1 at $DIR/if.rs:+2:27: +2:28
goto -> bb3; // scope 1 at $DIR/if.rs:+3:13: +3:41 goto -> bb3; // scope 1 at $DIR/if.rs:+2:13: +2:41
} }
bb2: { bb2: {
_2 = const 3_i32; // scope 1 at $DIR/if.rs:+3:38: +3:39 _2 = const 3_i32; // scope 1 at $DIR/if.rs:+2:38: +2:39
goto -> bb3; // scope 1 at $DIR/if.rs:+3:13: +3:41 goto -> bb3; // scope 1 at $DIR/if.rs:+2:13: +2:41
} }
bb3: { bb3: {
StorageDead(_3); // scope 1 at $DIR/if.rs:+3:40: +3:41 StorageDead(_3); // scope 1 at $DIR/if.rs:+2:40: +2:41
StorageLive(_6); // scope 2 at $DIR/if.rs:+4:9: +4:10 StorageLive(_6); // scope 2 at $DIR/if.rs:+3:9: +3:10
StorageLive(_7); // scope 2 at $DIR/if.rs:+4:13: +4:14 StorageLive(_7); // scope 2 at $DIR/if.rs:+3:13: +3:14
- _7 = _2; // scope 2 at $DIR/if.rs:+4:13: +4:14 - _7 = _2; // scope 2 at $DIR/if.rs:+3:13: +3:14
- _6 = Add(move _7, const 1_i32); // scope 2 at $DIR/if.rs:+4:13: +4:18 - _6 = Add(move _7, const 1_i32); // scope 2 at $DIR/if.rs:+3:13: +3:18
+ _7 = const 2_i32; // scope 2 at $DIR/if.rs:+4:13: +4:14 + _7 = const 2_i32; // scope 2 at $DIR/if.rs:+3:13: +3:14
+ _6 = const 3_i32; // scope 2 at $DIR/if.rs:+4:13: +4:18 + _6 = const 3_i32; // scope 2 at $DIR/if.rs:+3:13: +3:18
StorageDead(_7); // scope 2 at $DIR/if.rs:+4:17: +4:18 StorageDead(_7); // scope 2 at $DIR/if.rs:+3:17: +3:18
StorageLive(_8); // scope 3 at $DIR/if.rs:+6:9: +6:10 StorageLive(_8); // scope 3 at $DIR/if.rs:+5:9: +5:10
StorageLive(_9); // scope 3 at $DIR/if.rs:+6:16: +6:24 StorageLive(_9); // scope 3 at $DIR/if.rs:+5:16: +5:24
StorageLive(_10); // scope 3 at $DIR/if.rs:+6:16: +6:19 StorageLive(_10); // scope 3 at $DIR/if.rs:+5:16: +5:19
StorageLive(_11); // scope 3 at $DIR/if.rs:+6:17: +6:19 StorageLive(_11); // scope 3 at $DIR/if.rs:+5:17: +5:19
_11 = &_1; // scope 3 at $DIR/if.rs:+6:17: +6:19 _11 = &_1; // scope 3 at $DIR/if.rs:+5:17: +5:19
- _10 = (*_11); // scope 3 at $DIR/if.rs:+6:16: +6:19 - _10 = (*_11); // scope 3 at $DIR/if.rs:+5:16: +5:19
- _9 = Eq(move _10, const 1_i32); // scope 3 at $DIR/if.rs:+6:16: +6:24 - _9 = Eq(move _10, const 1_i32); // scope 3 at $DIR/if.rs:+5:16: +5:24
+ _10 = const 1_i32; // scope 3 at $DIR/if.rs:+6:16: +6:19 + _10 = const 1_i32; // scope 3 at $DIR/if.rs:+5:16: +5:19
+ _9 = const true; // scope 3 at $DIR/if.rs:+6:16: +6:24 + _9 = const true; // scope 3 at $DIR/if.rs:+5:16: +5:24
StorageDead(_11); // scope 3 at $DIR/if.rs:+6:23: +6:24 StorageDead(_11); // scope 3 at $DIR/if.rs:+5:23: +5:24
StorageDead(_10); // scope 3 at $DIR/if.rs:+6:23: +6:24 StorageDead(_10); // scope 3 at $DIR/if.rs:+5:23: +5:24
- switchInt(move _9) -> [false: bb5, otherwise: bb4]; // scope 3 at $DIR/if.rs:+6:16: +6:24 - switchInt(move _9) -> [false: bb5, otherwise: bb4]; // scope 3 at $DIR/if.rs:+5:16: +5:24
+ switchInt(const true) -> [false: bb5, otherwise: bb4]; // scope 3 at $DIR/if.rs:+6:16: +6:24 + switchInt(const true) -> [false: bb5, otherwise: bb4]; // scope 3 at $DIR/if.rs:+5:16: +5:24
} }
bb4: { bb4: {
- _8 = _1; // scope 3 at $DIR/if.rs:+6:27: +6:28 - _8 = _1; // scope 3 at $DIR/if.rs:+5:27: +5:28
+ _8 = const 1_i32; // scope 3 at $DIR/if.rs:+6:27: +6:28 + _8 = const 1_i32; // scope 3 at $DIR/if.rs:+5:27: +5:28
goto -> bb6; // scope 3 at $DIR/if.rs:+6:13: +6:45 goto -> bb6; // scope 3 at $DIR/if.rs:+5:13: +5:45
} }
bb5: { bb5: {
StorageLive(_12); // scope 3 at $DIR/if.rs:+6:38: +6:39 StorageLive(_12); // scope 3 at $DIR/if.rs:+5:38: +5:39
_12 = _1; // scope 3 at $DIR/if.rs:+6:38: +6:39 _12 = _1; // scope 3 at $DIR/if.rs:+5:38: +5:39
_8 = Add(move _12, const 1_i32); // scope 3 at $DIR/if.rs:+6:38: +6:43 _8 = Add(move _12, const 1_i32); // scope 3 at $DIR/if.rs:+5:38: +5:43
StorageDead(_12); // scope 3 at $DIR/if.rs:+6:42: +6:43 StorageDead(_12); // scope 3 at $DIR/if.rs:+5:42: +5:43
goto -> bb6; // scope 3 at $DIR/if.rs:+6:13: +6:45 goto -> bb6; // scope 3 at $DIR/if.rs:+5:13: +5:45
} }
bb6: { bb6: {
StorageDead(_9); // scope 3 at $DIR/if.rs:+6:44: +6:45 StorageDead(_9); // scope 3 at $DIR/if.rs:+5:44: +5:45
StorageLive(_13); // scope 4 at $DIR/if.rs:+7:9: +7:10 StorageLive(_13); // scope 4 at $DIR/if.rs:+6:9: +6:10
StorageLive(_14); // scope 4 at $DIR/if.rs:+7:13: +7:14 StorageLive(_14); // scope 4 at $DIR/if.rs:+6:13: +6:14
- _14 = _8; // scope 4 at $DIR/if.rs:+7:13: +7:14 - _14 = _8; // scope 4 at $DIR/if.rs:+6:13: +6:14
- _13 = Add(move _14, const 1_i32); // scope 4 at $DIR/if.rs:+7:13: +7:18 - _13 = Add(move _14, const 1_i32); // scope 4 at $DIR/if.rs:+6:13: +6:18
+ _14 = const 1_i32; // scope 4 at $DIR/if.rs:+7:13: +7:14 + _14 = const 1_i32; // scope 4 at $DIR/if.rs:+6:13: +6:14
+ _13 = const 2_i32; // scope 4 at $DIR/if.rs:+7:13: +7:18 + _13 = const 2_i32; // scope 4 at $DIR/if.rs:+6:13: +6:18
StorageDead(_14); // scope 4 at $DIR/if.rs:+7:17: +7:18 StorageDead(_14); // scope 4 at $DIR/if.rs:+6:17: +6:18
_0 = const (); // scope 0 at $DIR/if.rs:+0:11: +8:2 _0 = const (); // scope 0 at $DIR/if.rs:+0:11: +7:2
StorageDead(_13); // scope 4 at $DIR/if.rs:+8:1: +8:2 StorageDead(_13); // scope 4 at $DIR/if.rs:+7:1: +7:2
StorageDead(_8); // scope 3 at $DIR/if.rs:+8:1: +8:2 StorageDead(_8); // scope 3 at $DIR/if.rs:+7:1: +7:2
StorageDead(_6); // scope 2 at $DIR/if.rs:+8:1: +8:2 StorageDead(_6); // scope 2 at $DIR/if.rs:+7:1: +7:2
StorageDead(_2); // scope 1 at $DIR/if.rs:+8:1: +8:2 StorageDead(_2); // scope 1 at $DIR/if.rs:+7:1: +7:2
StorageDead(_1); // scope 0 at $DIR/if.rs:+8:1: +8:2 StorageDead(_1); // scope 0 at $DIR/if.rs:+7:1: +7:2
return; // scope 0 at $DIR/if.rs:+8:2: +8:2 return; // scope 0 at $DIR/if.rs:+7:2: +7:2
} }
} }

2
src/test/mir-opt/dataflow-const-prop/if.rs
View file

@ -1,8 +1,8 @@
// unit-test: DataflowConstProp // unit-test: DataflowConstProp
// compile-flags: -Zunsound-mir-opts
// EMIT_MIR if.main.DataflowConstProp.diff // EMIT_MIR if.main.DataflowConstProp.diff
fn main() { fn main() {
// This does not work (yet). Needs perhaps additional state to track unreachability.
let a = 1; let a = 1;
let b = if *&a == 1 { 2 } else { 3 }; let b = if *&a == 1 { 2 } else { 3 };
let c = b + 1; let c = b + 1;

2
src/test/mir-opt/dataflow-const-prop/ref.main.DataflowConstProp.diff
View file

@ -37,7 +37,7 @@
StorageLive(_6); // scope 2 at $DIR/ref.rs:+3:16: +3:34 StorageLive(_6); // scope 2 at $DIR/ref.rs:+3:16: +3:34
_6 = id() -> bb1; // scope 2 at $DIR/ref.rs:+3:16: +3:34 _6 = id() -> bb1; // scope 2 at $DIR/ref.rs:+3:16: +3:34
// mir::Constant // mir::Constant
// + span: $DIR/ref.rs:7:16: 7:32 // + span: $DIR/ref.rs:8:16: 8:32
// + literal: Const { ty: fn() -> u32 {id}, val: Value(<ZST>) } // + literal: Const { ty: fn() -> u32 {id}, val: Value(<ZST>) }
} }

1
src/test/mir-opt/dataflow-const-prop/ref.rs
View file

@ -1,4 +1,5 @@
// unit-test: DataflowConstProp // unit-test: DataflowConstProp
// compile-flags: -Zunsound-mir-opts
// EMIT_MIR ref.main.DataflowConstProp.diff // EMIT_MIR ref.main.DataflowConstProp.diff
fn main() { fn main() {