Skip to content

Commit

Permalink
Unrolled build for rust-lang#119077
Browse files Browse the repository at this point in the history
Rollup merge of rust-lang#119077 - tmiasko:lint, r=cjgillot

Separate MIR lints from validation

Add a MIR lint pass, enabled with -Zlint-mir, which identifies undefined or
likely erroneous behaviour.

The initial implementation mostly migrates existing checks of this nature from
MIR validator, where they did not belong (those checks have false positives and
there is nothing inherently invalid about MIR with undefined behaviour).

Fixes rust-lang#104736
Fixes rust-lang#104843
Fixes rust-lang#116079
Fixes rust-lang#116736
Fixes rust-lang#118990
  • Loading branch information
rust-timer authored Dec 23, 2023
2 parents 495203b + ba430a3 commit 1621059
Show file tree
Hide file tree
Showing 13 changed files with 196 additions and 56 deletions.
50 changes: 3 additions & 47 deletions compiler/rustc_const_eval/src/transform/validate.rs
Original file line number Diff line number Diff line change
Expand Up @@ -8,9 +8,6 @@ use rustc_middle::mir::interpret::Scalar;
use rustc_middle::mir::visit::{NonUseContext, PlaceContext, Visitor};
use rustc_middle::mir::*;
use rustc_middle::ty::{self, InstanceDef, ParamEnv, Ty, TyCtxt, TypeVisitableExt, Variance};
use rustc_mir_dataflow::impls::MaybeStorageLive;
use rustc_mir_dataflow::storage::always_storage_live_locals;
use rustc_mir_dataflow::{Analysis, ResultsCursor};
use rustc_target::abi::{Size, FIRST_VARIANT};
use rustc_target::spec::abi::Abi;

Expand Down Expand Up @@ -51,12 +48,6 @@ impl<'tcx> MirPass<'tcx> for Validator {
Reveal::All => tcx.param_env_reveal_all_normalized(def_id),
};

let always_live_locals = always_storage_live_locals(body);
let storage_liveness = MaybeStorageLive::new(std::borrow::Cow::Owned(always_live_locals))
.into_engine(tcx, body)
.iterate_to_fixpoint()
.into_results_cursor(body);

let can_unwind = if mir_phase <= MirPhase::Runtime(RuntimePhase::Initial) {
// In this case `AbortUnwindingCalls` haven't yet been executed.
true
Expand All @@ -83,7 +74,6 @@ impl<'tcx> MirPass<'tcx> for Validator {
mir_phase,
unwind_edge_count: 0,
reachable_blocks: traversal::reachable_as_bitset(body),
storage_liveness,
place_cache: FxHashSet::default(),
value_cache: FxHashSet::default(),
can_unwind,
Expand Down Expand Up @@ -116,7 +106,6 @@ struct CfgChecker<'a, 'tcx> {
mir_phase: MirPhase,
unwind_edge_count: usize,
reachable_blocks: BitSet<BasicBlock>,
storage_liveness: ResultsCursor<'a, 'tcx, MaybeStorageLive<'static>>,
place_cache: FxHashSet<PlaceRef<'tcx>>,
value_cache: FxHashSet<u128>,
// If `false`, then the MIR must not contain `UnwindAction::Continue` or
Expand Down Expand Up @@ -294,28 +283,13 @@ impl<'a, 'tcx> CfgChecker<'a, 'tcx> {
}

impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
fn visit_local(&mut self, local: Local, context: PlaceContext, location: Location) {
fn visit_local(&mut self, local: Local, _context: PlaceContext, location: Location) {
if self.body.local_decls.get(local).is_none() {
self.fail(
location,
format!("local {local:?} has no corresponding declaration in `body.local_decls`"),
);
}

if self.reachable_blocks.contains(location.block) && context.is_use() {
// We check that the local is live whenever it is used. Technically, violating this
// restriction is only UB and not actually indicative of not well-formed MIR. This means
// that an optimization which turns MIR that already has UB into MIR that fails this
// check is not necessarily wrong. However, we have no such optimizations at the moment,
// and so we include this check anyway to help us catch bugs. If you happen to write an
// optimization that might cause this to incorrectly fire, feel free to remove this
// check.
self.storage_liveness.seek_after_primary_effect(location);
let locals_with_storage = self.storage_liveness.get();
if !locals_with_storage.contains(local) {
self.fail(location, format!("use of local {local:?}, which has no storage here"));
}
}
}

fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
Expand Down Expand Up @@ -367,26 +341,8 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
self.fail(location, format!("explicit `{kind:?}` is forbidden"));
}
}
StatementKind::StorageLive(local) => {
// We check that the local is not live when entering a `StorageLive` for it.
// Technically, violating this restriction is only UB and not actually indicative
// of not well-formed MIR. This means that an optimization which turns MIR that
// already has UB into MIR that fails this check is not necessarily wrong. However,
// we have no such optimizations at the moment, and so we include this check anyway
// to help us catch bugs. If you happen to write an optimization that might cause
// this to incorrectly fire, feel free to remove this check.
if self.reachable_blocks.contains(location.block) {
self.storage_liveness.seek_before_primary_effect(location);
let locals_with_storage = self.storage_liveness.get();
if locals_with_storage.contains(*local) {
self.fail(
location,
format!("StorageLive({local:?}) which already has storage here"),
);
}
}
}
StatementKind::StorageDead(_)
StatementKind::StorageLive(_)
| StatementKind::StorageDead(_)
| StatementKind::Intrinsic(_)
| StatementKind::Coverage(_)
| StatementKind::ConstEvalCounter
Expand Down
12 changes: 6 additions & 6 deletions compiler/rustc_mir_dataflow/src/impls/storage_liveness.rs
Original file line number Diff line number Diff line change
Expand Up @@ -81,17 +81,17 @@ impl<'tcx, 'a> crate::GenKillAnalysis<'tcx> for MaybeStorageLive<'a> {
}

#[derive(Clone)]
pub struct MaybeStorageDead {
always_live_locals: BitSet<Local>,
pub struct MaybeStorageDead<'a> {
always_live_locals: Cow<'a, BitSet<Local>>,
}

impl MaybeStorageDead {
pub fn new(always_live_locals: BitSet<Local>) -> Self {
impl<'a> MaybeStorageDead<'a> {
pub fn new(always_live_locals: Cow<'a, BitSet<Local>>) -> Self {
MaybeStorageDead { always_live_locals }
}
}

impl<'tcx> crate::AnalysisDomain<'tcx> for MaybeStorageDead {
impl<'tcx, 'a> crate::AnalysisDomain<'tcx> for MaybeStorageDead<'a> {
type Domain = BitSet<Local>;

const NAME: &'static str = "maybe_storage_dead";
Expand All @@ -112,7 +112,7 @@ impl<'tcx> crate::AnalysisDomain<'tcx> for MaybeStorageDead {
}
}

impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeStorageDead {
impl<'tcx, 'a> crate::GenKillAnalysis<'tcx> for MaybeStorageDead<'a> {
type Idx = Local;

fn domain_size(&self, body: &Body<'tcx>) -> usize {
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_mir_transform/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,7 @@ pub mod inline;
mod instsimplify;
mod jump_threading;
mod large_enums;
mod lint;
mod lower_intrinsics;
mod lower_slice_len;
mod match_branches;
Expand Down
119 changes: 119 additions & 0 deletions compiler/rustc_mir_transform/src/lint.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,119 @@
//! 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_index::bit_set::BitSet;
use rustc_middle::mir::visit::{PlaceContext, Visitor};
use rustc_middle::mir::*;
use rustc_middle::ty::TyCtxt;
use rustc_mir_dataflow::impls::{MaybeStorageDead, MaybeStorageLive};
use rustc_mir_dataflow::storage::always_storage_live_locals;
use rustc_mir_dataflow::{Analysis, ResultsCursor};
use std::borrow::Cow;

pub fn lint_body<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, when: String) {
let reachable_blocks = traversal::reachable_as_bitset(body);
let always_live_locals = &always_storage_live_locals(body);

let maybe_storage_live = MaybeStorageLive::new(Cow::Borrowed(always_live_locals))
.into_engine(tcx, body)
.iterate_to_fixpoint()
.into_results_cursor(body);

let maybe_storage_dead = MaybeStorageDead::new(Cow::Borrowed(always_live_locals))
.into_engine(tcx, body)
.iterate_to_fixpoint()
.into_results_cursor(body);

Lint {
tcx,
when,
body,
is_fn_like: tcx.def_kind(body.source.def_id()).is_fn_like(),
always_live_locals,
reachable_blocks,
maybe_storage_live,
maybe_storage_dead,
}
.visit_body(body);
}

struct Lint<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
when: String,
body: &'a Body<'tcx>,
is_fn_like: bool,
always_live_locals: &'a BitSet<Local>,
reachable_blocks: BitSet<BasicBlock>,
maybe_storage_live: ResultsCursor<'a, 'tcx, MaybeStorageLive<'a>>,
maybe_storage_dead: ResultsCursor<'a, 'tcx, MaybeStorageDead<'a>>,
}

impl<'a, 'tcx> Lint<'a, 'tcx> {
#[track_caller]
fn fail(&self, location: Location, msg: impl AsRef<str>) {
let span = self.body.source_info(location).span;
self.tcx.sess.dcx().span_delayed_bug(
span,
format!(
"broken MIR in {:?} ({}) at {:?}:\n{}",
self.body.source.instance,
self.when,
location,
msg.as_ref()
),
);
}
}

impl<'a, 'tcx> Visitor<'tcx> for Lint<'a, 'tcx> {
fn visit_local(&mut self, local: Local, context: PlaceContext, location: Location) {
if self.reachable_blocks.contains(location.block) && context.is_use() {
self.maybe_storage_dead.seek_after_primary_effect(location);
if self.maybe_storage_dead.get().contains(local) {
self.fail(location, format!("use of local {local:?}, which has no storage here"));
}
}
}

fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
match statement.kind {
StatementKind::StorageLive(local) => {
if self.reachable_blocks.contains(location.block) {
self.maybe_storage_live.seek_before_primary_effect(location);
if self.maybe_storage_live.get().contains(local) {
self.fail(
location,
format!("StorageLive({local:?}) which already has storage here"),
);
}
}
}
_ => {}
}

self.super_statement(statement, location);
}

fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
match terminator.kind {
TerminatorKind::Return => {
if self.is_fn_like && self.reachable_blocks.contains(location.block) {
self.maybe_storage_live.seek_after_primary_effect(location);
for local in self.maybe_storage_live.get().iter() {
if !self.always_live_locals.contains(local) {
self.fail(
location,
format!(
"local {local:?} still has storage when returning from function"
),
);
}
}
}
}
_ => {}
}

self.super_terminator(terminator, location);
}
}
12 changes: 11 additions & 1 deletion compiler/rustc_mir_transform/src/pass_manager.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ use rustc_middle::mir::{self, Body, MirPhase, RuntimePhase};
use rustc_middle::ty::TyCtxt;
use rustc_session::Session;

use crate::{validate, MirPass};
use crate::{lint::lint_body, validate, MirPass};

/// Just like `MirPass`, except it cannot mutate `Body`.
pub trait MirLint<'tcx> {
Expand Down Expand Up @@ -109,6 +109,7 @@ fn run_passes_inner<'tcx>(
phase_change: Option<MirPhase>,
validate_each: bool,
) {
let lint = tcx.sess.opts.unstable_opts.lint_mir & !body.should_skip();
let validate = validate_each & tcx.sess.opts.unstable_opts.validate_mir & !body.should_skip();
let overridden_passes = &tcx.sess.opts.unstable_opts.mir_enable_passes;
trace!(?overridden_passes);
Expand All @@ -131,6 +132,9 @@ fn run_passes_inner<'tcx>(
if validate {
validate_body(tcx, body, format!("before pass {name}"));
}
if lint {
lint_body(tcx, body, format!("before pass {name}"));
}

if let Some(prof_arg) = &prof_arg {
tcx.sess
Expand All @@ -147,6 +151,9 @@ fn run_passes_inner<'tcx>(
if validate {
validate_body(tcx, body, format!("after pass {name}"));
}
if lint {
lint_body(tcx, body, format!("after pass {name}"));
}

body.pass_count += 1;
}
Expand All @@ -164,6 +171,9 @@ fn run_passes_inner<'tcx>(
if validate || new_phase == MirPhase::Runtime(RuntimePhase::Optimized) {
validate_body(tcx, body, format!("after phase change to {}", new_phase.name()));
}
if lint {
lint_body(tcx, body, format!("after phase change to {}", new_phase.name()));
}

body.pass_count = 1;
}
Expand Down
3 changes: 2 additions & 1 deletion compiler/rustc_mir_transform/src/ref_prop.rs
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ use rustc_middle::ty::TyCtxt;
use rustc_mir_dataflow::impls::MaybeStorageDead;
use rustc_mir_dataflow::storage::always_storage_live_locals;
use rustc_mir_dataflow::Analysis;
use std::borrow::Cow;

use crate::ssa::{SsaLocals, StorageLiveLocals};

Expand Down Expand Up @@ -120,7 +121,7 @@ fn compute_replacement<'tcx>(

// Compute `MaybeStorageDead` dataflow to check that we only replace when the pointee is
// definitely live.
let mut maybe_dead = MaybeStorageDead::new(always_live_locals)
let mut maybe_dead = MaybeStorageDead::new(Cow::Owned(always_live_locals))
.into_engine(tcx, body)
.iterate_to_fixpoint()
.into_results_cursor(body);
Expand Down
2 changes: 2 additions & 0 deletions compiler/rustc_session/src/options.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1694,6 +1694,8 @@ options! {
"link native libraries in the linker invocation (default: yes)"),
link_only: bool = (false, parse_bool, [TRACKED],
"link the `.rlink` file generated by `-Z no-link` (default: no)"),
lint_mir: bool = (false, parse_bool, [UNTRACKED],
"lint MIR before and after each transformation"),
llvm_module_flag: Vec<(String, u32, String)> = (Vec::new(), parse_llvm_module_flag, [TRACKED],
"a list of module flags to pass to LLVM (space separated)"),
llvm_plugins: Vec<String> = (Vec::new(), parse_list, [TRACKED],
Expand Down
1 change: 1 addition & 0 deletions src/tools/compiletest/src/runtest.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2445,6 +2445,7 @@ impl<'test> TestCx<'test> {
"-Copt-level=1",
&zdump_arg,
"-Zvalidate-mir",
"-Zlint-mir",
"-Zdump-mir-exclude-pass-number",
]);
if let Some(pass) = &self.props.mir_unit_test {
Expand Down
1 change: 1 addition & 0 deletions tests/mir-opt/reference_prop.rs
Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
// compile-flags: -Zlint-mir=no
// unit-test: ReferencePropagation
// needs-unwind

Expand Down
30 changes: 30 additions & 0 deletions tests/ui/mir/lint/no-storage.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
// compile-flags: -Zlint-mir --crate-type=lib -Ztreat-err-as-bug
// failure-status: 101
// dont-check-compiler-stderr
// regex-error-pattern: use of local .*, which has no storage here
#![feature(custom_mir, core_intrinsics)]
extern crate core;
use core::intrinsics::mir::*;

#[custom_mir(dialect = "built")]
pub fn f(a: bool) {
mir!(
let b: ();
{
match a { true => bb1, _ => bb2 }
}
bb1 = {
StorageLive(b);
Goto(bb3)
}
bb2 = {
Goto(bb3)
}
bb3 = {
b = ();
RET = b;
StorageDead(b);
Return()
}
)
}
Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
// compile-flags: -Zvalidate-mir -Ztreat-err-as-bug
// compile-flags: -Zlint-mir -Ztreat-err-as-bug
// failure-status: 101
// error-pattern: broken MIR in
// error-pattern: StorageLive(_1) which already has storage here
Expand Down
File renamed without changes.
Loading

0 comments on commit 1621059

Please sign in to comment.