nordic-dev.net/rust
nordic-dev.net/rust
2
0
Fork 0
mirror of https://github.com/rust-lang/rust.git synced 2024-10-31 06:22:00 +00:00
Code Issues Packages Projects Releases Wiki Activity

Migrate memory overlap check from validator to lint

Browse Source 
The check attempts to identify potential undefined behaviour, rather
than whether MIR is well-formed. It belongs in the lint not validator.
This commit is contained in:
Tomasz Miąsko 2024-01-04 14:24:41 +01:00
parent a084e063e6
commit df116ec246
8 changed files with 85 additions and 237 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
compiler/rustc_const_eval/src/transform/validate.rs
View File

@ -74,7 +74,6 @@ impl<'tcx> MirPass<'tcx> for Validator {
mir_phase,
unwind_edge_count: 0,
reachable_blocks: traversal::reachable_as_bitset(body),
place_cache: FxHashSet::default(),
value_cache: FxHashSet::default(),
can_unwind,
};
@ -106,7 +105,6 @@ struct CfgChecker<'a, 'tcx> {
mir_phase: MirPhase,
unwind_edge_count: usize,
reachable_blocks: BitSet<BasicBlock>,
place_cache: FxHashSet<PlaceRef<'tcx>>,
value_cache: FxHashSet<u128>,
// If `false`, then the MIR must not contain `UnwindAction::Continue` or
// `TerminatorKind::Resume`.
@ -294,19 +292,6 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
match &statement.kind {
StatementKind::Assign(box (dest, rvalue)) => {
// FIXME(JakobDegen): Check this for all rvalues, not just this one.
if let Rvalue::Use(Operand::Copy(src) | Operand::Move(src)) = rvalue {
// The sides of an assignment must not alias. Currently this just checks whether
// the places are identical.
if dest == src {
self.fail(
location,
"encountered `Assign` statement with overlapping memory",
);
}
}
}
StatementKind::AscribeUserType(..) => {
if self.mir_phase >= MirPhase::Runtime(RuntimePhase::Initial) {
self.fail(
@ -341,7 +326,8 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
self.fail(location, format!("explicit `{kind:?}` is forbidden"));
}
}
StatementKind::StorageLive(_)
StatementKind::Assign(..)
| StatementKind::StorageLive(_)
| StatementKind::StorageDead(_)
| StatementKind::Intrinsic(_)
| StatementKind::Coverage(_)
@ -404,10 +390,7 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
}
// The call destination place and Operand::Move place used as an argument might be
// passed by a reference to the callee. Consequently they must be non-overlapping
// and cannot be packed. Currently this simply checks for duplicate places.
self.place_cache.clear();
self.place_cache.insert(destination.as_ref());
// passed by a reference to the callee. Consequently they cannot be packed.
if is_within_packed(self.tcx, &self.body.local_decls, *destination).is_some() {
// This is bad! The callee will expect the memory to be aligned.
self.fail(
@ -418,10 +401,8 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
),
);
}
let mut has_duplicates = false;
for arg in args {
if let Operand::Move(place) = arg {
has_duplicates |= !self.place_cache.insert(place.as_ref());
if is_within_packed(self.tcx, &self.body.local_decls, *place).is_some() {
// This is bad! The callee will expect the memory to be aligned.
self.fail(
@ -434,16 +415,6 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
}
}
}
if has_duplicates {
self.fail(
location,
format!(
"encountered overlapping memory in `Move` arguments to `Call` terminator: {:?}",
terminator.kind,
),
);
}
}
TerminatorKind::Assert { target, unwind, .. } => {
self.check_edge(location, *target, EdgeKind::Normal);
@ -1112,17 +1083,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
)
}
}
// FIXME(JakobDegen): Check this for all rvalues, not just this one.
if let Rvalue::Use(Operand::Copy(src) | Operand::Move(src)) = rvalue {
// The sides of an assignment must not alias. Currently this just checks whether
// the places are identical.
if dest == src {
self.fail(
location,
"encountered `Assign` statement with overlapping memory",
);
}
}
}
StatementKind::AscribeUserType(..) => {
if self.mir_phase >= MirPhase::Runtime(RuntimePhase::Initial) {

7
compiler/rustc_mir_transform/src/dest_prop.rs
View File

@ -133,7 +133,6 @@
use std::collections::hash_map::{Entry, OccupiedEntry};
use crate::simplify::remove_dead_blocks;
use crate::MirPass;
use rustc_data_structures::fx::FxHashMap;
use rustc_index::bit_set::BitSet;
@ -241,12 +240,6 @@ impl<'tcx> MirPass<'tcx> for DestinationPropagation {
apply_merges(body, tcx, &merges, &merged_locals);
}
if round_count != 0 {
// Merging can introduce overlap between moved arguments and/or call destination in an
// unreachable code, which validator considers to be ill-formed.
remove_dead_blocks(body);
}
trace!(round_count);
}
}

43
compiler/rustc_mir_transform/src/lint.rs
View File

@ -1,6 +1,7 @@
//! This pass statically detects code which has undefined behaviour or is likely to be erroneous.
//! It can be used to locate problems in MIR building or optimizations. It assumes that all code
//! can be executed, so it has false positives.
use rustc_data_structures::fx::FxHashSet;
use rustc_index::bit_set::BitSet;
use rustc_middle::mir::visit::{PlaceContext, Visitor};
use rustc_middle::mir::*;
@ -31,6 +32,7 @@ pub fn lint_body<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, when: String) {
always_live_locals,
maybe_storage_live,
maybe_storage_dead,
places: Default::default(),
};
for (bb, data) in traversal::reachable(body) {
lint.visit_basic_block_data(bb, data);
@ -45,6 +47,7 @@ struct Lint<'a, 'tcx> {
always_live_locals: &'a BitSet<Local>,
maybe_storage_live: ResultsCursor<'a, 'tcx, MaybeStorageLive<'a>>,
maybe_storage_dead: ResultsCursor<'a, 'tcx, MaybeStorageDead<'a>>,
places: FxHashSet<PlaceRef<'tcx>>,
}
impl<'a, 'tcx> Lint<'a, 'tcx> {
@ -75,10 +78,22 @@ impl<'a, 'tcx> Visitor<'tcx> for Lint<'a, 'tcx> {
}
fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
match statement.kind {
match &statement.kind {
StatementKind::Assign(box (dest, rvalue)) => {
if let Rvalue::Use(Operand::Copy(src) | Operand::Move(src)) = rvalue {
// The sides of an assignment must not alias. Currently this just checks whether
// the places are identical.
if dest == src {
self.fail(
location,
"encountered `Assign` statement with overlapping memory",
);
}
}
}
StatementKind::StorageLive(local) => {
self.maybe_storage_live.seek_before_primary_effect(location);
if self.maybe_storage_live.get().contains(local) {
if self.maybe_storage_live.get().contains(*local) {
self.fail(
location,
format!("StorageLive({local:?}) which already has storage here"),
@ -92,7 +107,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Lint<'a, 'tcx> {
}
fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
match terminator.kind {
match &terminator.kind {
TerminatorKind::Return => {
if self.is_fn_like {
self.maybe_storage_live.seek_after_primary_effect(location);
@ -108,6 +123,28 @@ impl<'a, 'tcx> Visitor<'tcx> for Lint<'a, 'tcx> {
}
}
}
TerminatorKind::Call { args, destination, .. } => {
// The call destination place and Operand::Move place used as an argument might be
// passed by a reference to the callee. Consequently they must be non-overlapping.
// Currently this simply checks for duplicate places.
self.places.clear();
self.places.insert(destination.as_ref());
let mut has_duplicates = false;
for arg in args {
if let Operand::Move(place) = arg {
has_duplicates |= !self.places.insert(place.as_ref());
}
}
if has_duplicates {
self.fail(
location,
format!(
"encountered overlapping memory in `Move` arguments to `Call` terminator: {:?}",
terminator.kind,
),
);
}
}
_ => {}
}

82
tests/mir-opt/dest-prop/unreachable.f.DestinationPropagation.panic-abort.diff
View File

@ -1,82 +0,0 @@
- // MIR for `f` before DestinationPropagation
+ // MIR for `f` after DestinationPropagation
fn f(_1: T) -> () {
debug a => _1;
let mut _0: ();
let _2: T;
let mut _3: bool;
let _4: ();
let mut _5: T;
let mut _6: T;
let _7: ();
let mut _8: T;
let mut _9: T;
scope 1 {
- debug b => _2;
+ debug b => _1;
}
bb0: {
- StorageLive(_2);
- _2 = _1;
+ nop;
+ nop;
StorageLive(_3);
_3 = const false;
- goto -> bb3;
+ goto -> bb1;
}
bb1: {
- StorageLive(_4);
- StorageLive(_5);
- _5 = _1;
- StorageLive(_6);
- _6 = _1;
- _4 = g::<T>(_1, _1) -> [return: bb2, unwind unreachable];
- }
-
- bb2: {
- StorageDead(_6);
- StorageDead(_5);
- StorageDead(_4);
- _0 = const ();
- goto -> bb5;
- }
-
- bb3: {
StorageLive(_7);
- StorageLive(_8);
- _8 = _1;
- StorageLive(_9);
- _9 = _1;
- _7 = g::<T>(_1, _1) -> [return: bb4, unwind unreachable];
+ nop;
+ nop;
+ nop;
+ nop;
+ _7 = g::<T>(_1, _1) -> [return: bb2, unwind unreachable];
}
- bb4: {
- StorageDead(_9);
- StorageDead(_8);
+ bb2: {
+ nop;
+ nop;
StorageDead(_7);
_0 = const ();
- goto -> bb5;
+ goto -> bb3;
}
- bb5: {
+ bb3: {
StorageDead(_3);
- StorageDead(_2);
+ nop;
return;
}
}

82
tests/mir-opt/dest-prop/unreachable.f.DestinationPropagation.panic-unwind.diff
View File

@ -1,82 +0,0 @@
- // MIR for `f` before DestinationPropagation
+ // MIR for `f` after DestinationPropagation
fn f(_1: T) -> () {
debug a => _1;
let mut _0: ();
let _2: T;
let mut _3: bool;
let _4: ();
let mut _5: T;
let mut _6: T;
let _7: ();
let mut _8: T;
let mut _9: T;
scope 1 {
- debug b => _2;
+ debug b => _1;
}
bb0: {
- StorageLive(_2);
- _2 = _1;
+ nop;
+ nop;
StorageLive(_3);
_3 = const false;
- goto -> bb3;
+ goto -> bb1;
}
bb1: {
- StorageLive(_4);
- StorageLive(_5);
- _5 = _1;
- StorageLive(_6);
- _6 = _1;
- _4 = g::<T>(_1, _1) -> [return: bb2, unwind continue];
- }
-
- bb2: {
- StorageDead(_6);
- StorageDead(_5);
- StorageDead(_4);
- _0 = const ();
- goto -> bb5;
- }
-
- bb3: {
StorageLive(_7);
- StorageLive(_8);
- _8 = _1;
- StorageLive(_9);
- _9 = _1;
- _7 = g::<T>(_1, _1) -> [return: bb4, unwind continue];
+ nop;
+ nop;
+ nop;
+ nop;
+ _7 = g::<T>(_1, _1) -> [return: bb2, unwind continue];
}
- bb4: {
- StorageDead(_9);
- StorageDead(_8);
+ bb2: {
+ nop;
+ nop;
StorageDead(_7);
_0 = const ();
- goto -> bb5;
+ goto -> bb3;
}
- bb5: {
+ bb3: {
StorageDead(_3);
- StorageDead(_2);
+ nop;
return;
}
}

20
tests/mir-opt/dest-prop/unreachable.rs
View File

@ -1,20 +0,0 @@
// skip-filecheck
// EMIT_MIR_FOR_EACH_PANIC_STRATEGY
// Check that unreachable code is removed after the destination propagation.
// Regression test for issue #105428.
//
// compile-flags: --crate-type=lib -Zmir-opt-level=0
// compile-flags: -Zmir-enable-passes=+GVN,+SimplifyConstCondition-after-const-prop,+DestinationPropagation
// EMIT_MIR unreachable.f.DestinationPropagation.diff
pub fn f<T: Copy>(a: T) {
let b = a;
if false {
g(a, b);
} else {
g(b, b);
}
}
#[inline(never)]
pub fn g<T: Copy>(_: T, _: T) {}

19
tests/ui/mir/lint/assignment-overlap.rs Normal file
View File

@ -0,0 +1,19 @@
// compile-flags: --crate-type=lib -Zlint-mir -Ztreat-err-as-bug
// build-fail
// failure-status: 101
// dont-check-compiler-stderr
// error-pattern: encountered `Assign` statement with overlapping memory
#![feature(custom_mir, core_intrinsics)]
extern crate core;
use core::intrinsics::mir::*;
#[custom_mir(dialect = "runtime", phase = "optimized")]
pub fn main() {
mir!(
let a: [u8; 1024];
{
a = a;
Return()
}
)
}

23
tests/ui/mir/lint/call-overlap.rs Normal file
View File

@ -0,0 +1,23 @@
// compile-flags: -Zlint-mir -Ztreat-err-as-bug
// build-fail
// failure-status: 101
// dont-check-compiler-stderr
// error-pattern: encountered overlapping memory in `Move` arguments to `Call`
#![feature(custom_mir, core_intrinsics)]
extern crate core;
use core::intrinsics::mir::*;
#[custom_mir(dialect = "runtime", phase = "optimized")]
pub fn main() {
mir!(
let a: [u8; 1024];
{
Call(a = f(Move(a)), ReturnTo(bb1), UnwindUnreachable())
}
bb1 = {
Return()
}
)
}
pub fn f<T: Copy>(a: T) -> T { a }