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Rollup merge of #65839 - ecstatic-morse:promo-sanity-fixes, r=eddyb 

Clean up `check_consts` now that new promotion pass is implemented

`check_consts::resolver` contained a layer of abstraction (`QualifResolver`) to allow the existing, eager style of qualif propagation to work with either a dataflow results cursor or by applying the transfer function directly (if dataflow was not needed e.g. for promotion). However, #63812 uses a different, lazy paradigm for checking promotability, which makes this unnecessary. This PR cleans up `check_consts::validation` to use `FlowSensitiveResolver` directly, instead of through the now obselete `QualifResolver` API.

Also, this contains a few commits (the first four) that address some FIXMEs in #63812 regarding code duplication. They could be split out, but I think they will be relatively noncontroversial? Notably, `validation::Mode` is renamed to `ConstKind` and used in `promote_consts` to denote what kind of item we are in.

This is best reviewed commit-by-commit and is low priority.

r? @eddyb
This commit is contained in:
Mazdak Farrokhzad 2019-10-27 16:46:56 +01:00 committed by GitHub
parent 0982060a69 b93cdbce36
commit dae8ded9f5
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GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 242 additions and 373 deletions
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109
src/librustc_mir/transform/check_consts/mod.rs
View File

@ -4,10 +4,12 @@
//! has interior mutability or needs to be dropped, as well as the visitor that emits errors when
//! it finds operations that are invalid in a certain context.
use rustc::hir::def_id::DefId;
use rustc::hir::{self, def_id::DefId};
use rustc::mir;
use rustc::ty::{self, TyCtxt};
use std::fmt;
pub use self::qualifs::Qualif;
pub mod ops;
@ -15,15 +17,14 @@ pub mod qualifs;
mod resolver;
pub mod validation;
/// Information about the item currently being validated, as well as a reference to the global
/// Information about the item currently being const-checked, as well as a reference to the global
/// context.
pub struct Item<'mir, 'tcx> {
body: &'mir mir::Body<'tcx>,
tcx: TyCtxt<'tcx>,
def_id: DefId,
param_env: ty::ParamEnv<'tcx>,
mode: validation::Mode,
for_promotion: bool,
pub body: &'mir mir::Body<'tcx>,
pub tcx: TyCtxt<'tcx>,
pub def_id: DefId,
pub param_env: ty::ParamEnv<'tcx>,
pub const_kind: Option<ConstKind>,
}
impl Item<'mir, 'tcx> {
@ -33,43 +34,91 @@ impl Item<'mir, 'tcx> {
body: &'mir mir::Body<'tcx>,
) -> Self {
let param_env = tcx.param_env(def_id);
let mode = validation::Mode::for_item(tcx, def_id)
.expect("const validation must only be run inside a const context");
let const_kind = ConstKind::for_item(tcx, def_id);
Item {
body,
tcx,
def_id,
param_env,
mode,
for_promotion: false,
const_kind,
}
}
// HACK(eddyb) this is to get around the panic for a runtime fn from `Item::new`.
// Also, it allows promoting `&mut []`.
pub fn for_promotion(
tcx: TyCtxt<'tcx>,
def_id: DefId,
body: &'mir mir::Body<'tcx>,
) -> Self {
let param_env = tcx.param_env(def_id);
let mode = validation::Mode::for_item(tcx, def_id)
.unwrap_or(validation::Mode::ConstFn);
/// Returns the kind of const context this `Item` represents (`const`, `static`, etc.).
///
/// Panics if this `Item` is not const.
pub fn const_kind(&self) -> ConstKind {
self.const_kind.expect("`const_kind` must not be called on a non-const fn")
}
}
Item {
body,
tcx,
def_id,
param_env,
mode,
for_promotion: true,
/// The kinds of items which require compile-time evaluation.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum ConstKind {
/// A `static` item.
Static,
/// A `static mut` item.
StaticMut,
/// A `const fn` item.
ConstFn,
/// A `const` item or an anonymous constant (e.g. in array lengths).
Const,
}
impl ConstKind {
/// Returns the validation mode for the item with the given `DefId`, or `None` if this item
/// does not require validation (e.g. a non-const `fn`).
pub fn for_item(tcx: TyCtxt<'tcx>, def_id: DefId) -> Option<Self> {
use hir::BodyOwnerKind as HirKind;
let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
let mode = match tcx.hir().body_owner_kind(hir_id) {
HirKind::Closure => return None,
HirKind::Fn if tcx.is_const_fn(def_id) => ConstKind::ConstFn,
HirKind::Fn => return None,
HirKind::Const => ConstKind::Const,
HirKind::Static(hir::MutImmutable) => ConstKind::Static,
HirKind::Static(hir::MutMutable) => ConstKind::StaticMut,
};
Some(mode)
}
pub fn is_static(self) -> bool {
match self {
ConstKind::Static | ConstKind::StaticMut => true,
ConstKind::ConstFn | ConstKind::Const => false,
}
}
/// Returns `true` if the value returned by this item must be `Sync`.
///
/// This returns false for `StaticMut` since all accesses to one are `unsafe` anyway.
pub fn requires_sync(self) -> bool {
match self {
ConstKind::Static => true,
ConstKind::ConstFn | ConstKind::Const | ConstKind::StaticMut => false,
}
}
}
impl fmt::Display for ConstKind {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match *self {
ConstKind::Const => write!(f, "constant"),
ConstKind::Static | ConstKind::StaticMut => write!(f, "static"),
ConstKind::ConstFn => write!(f, "constant function"),
}
}
}
fn is_lang_panic_fn(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
/// Returns `true` if this `DefId` points to one of the official `panic` lang items.
pub fn is_lang_panic_fn(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
Some(def_id) == tcx.lang_items().panic_fn() ||
Some(def_id) == tcx.lang_items().begin_panic_fn()
}

33
src/librustc_mir/transform/check_consts/ops.rs
View File

@ -8,8 +8,7 @@ use syntax::feature_gate::{emit_feature_err, GateIssue};
use syntax::symbol::sym;
use syntax_pos::{Span, Symbol};
use super::Item;
use super::validation::Mode;
use super::{ConstKind, Item};
/// An operation that is not *always* allowed in a const context.
pub trait NonConstOp: std::fmt::Debug {
@ -36,7 +35,7 @@ pub trait NonConstOp: std::fmt::Debug {
span,
E0019,
"{} contains unimplemented expression type",
item.mode
item.const_kind()
);
if item.tcx.sess.teach(&err.get_code().unwrap()) {
err.note("A function call isn't allowed in the const's initialization expression \
@ -76,7 +75,7 @@ impl NonConstOp for FnCallNonConst {
E0015,
"calls in {}s are limited to constant functions, \
tuple structs and tuple variants",
item.mode,
item.const_kind(),
);
err.emit();
}
@ -121,8 +120,8 @@ impl NonConstOp for HeapAllocation {
fn emit_error(&self, item: &Item<'_, '_>, span: Span) {
let mut err = struct_span_err!(item.tcx.sess, span, E0010,
"allocations are not allowed in {}s", item.mode);
err.span_label(span, format!("allocation not allowed in {}s", item.mode));
"allocations are not allowed in {}s", item.const_kind());
err.span_label(span, format!("allocation not allowed in {}s", item.const_kind()));
if item.tcx.sess.teach(&err.get_code().unwrap()) {
err.note(
"The value of statics and constants must be known at compile time, \
@ -146,7 +145,7 @@ impl NonConstOp for LiveDrop {
struct_span_err!(item.tcx.sess, span, E0493,
"destructors cannot be evaluated at compile-time")
.span_label(span, format!("{}s cannot evaluate destructors",
item.mode))
item.const_kind()))
.emit();
}
}
@ -163,9 +162,9 @@ impl NonConstOp for MutBorrow {
if let BorrowKind::Mut { .. } = kind {
let mut err = struct_span_err!(item.tcx.sess, span, E0017,
"references in {}s may only refer \
to immutable values", item.mode);
to immutable values", item.const_kind());
err.span_label(span, format!("{}s require immutable values",
item.mode));
item.const_kind()));
if item.tcx.sess.teach(&err.get_code().unwrap()) {
err.note("References in statics and constants may only refer \
to immutable values.\n\n\
@ -202,7 +201,7 @@ impl NonConstOp for Panic {
sym::const_panic,
span,
GateIssue::Language,
&format!("panicking in {}s is unstable", item.mode),
&format!("panicking in {}s is unstable", item.const_kind()),
);
}
}
@ -220,7 +219,7 @@ impl NonConstOp for RawPtrComparison {
sym::const_compare_raw_pointers,
span,
GateIssue::Language,
&format!("comparing raw pointers inside {}", item.mode),
&format!("comparing raw pointers inside {}", item.const_kind()),
);
}
}
@ -238,7 +237,7 @@ impl NonConstOp for RawPtrDeref {
span, GateIssue::Language,
&format!(
"dereferencing raw pointers in {}s is unstable",
item.mode,
item.const_kind(),
),
);
}
@ -257,7 +256,7 @@ impl NonConstOp for RawPtrToIntCast {
span, GateIssue::Language,
&format!(
"casting pointers to integers in {}s is unstable",
item.mode,
item.const_kind(),
),
);
}
@ -268,13 +267,13 @@ impl NonConstOp for RawPtrToIntCast {
pub struct StaticAccess;
impl NonConstOp for StaticAccess {
fn is_allowed_in_item(&self, item: &Item<'_, '_>) -> bool {
item.mode.is_static()
item.const_kind().is_static()
}
fn emit_error(&self, item: &Item<'_, '_>, span: Span) {
let mut err = struct_span_err!(item.tcx.sess, span, E0013,
"{}s cannot refer to statics, use \
a constant instead", item.mode);
a constant instead", item.const_kind());
if item.tcx.sess.teach(&err.get_code().unwrap()) {
err.note(
"Static and const variables can refer to other const variables. \
@ -313,7 +312,7 @@ impl NonConstOp for Transmute {
&item.tcx.sess.parse_sess, sym::const_transmute,
span, GateIssue::Language,
&format!("The use of std::mem::transmute() \
is gated in {}s", item.mode));
is gated in {}s", item.const_kind()));
}
}
@ -322,7 +321,7 @@ pub struct UnionAccess;
impl NonConstOp for UnionAccess {
fn is_allowed_in_item(&self, item: &Item<'_, '_>) -> bool {
// Union accesses are stable in all contexts except `const fn`.
item.mode != Mode::ConstFn || Self::feature_gate(item.tcx).unwrap()
item.const_kind() != ConstKind::ConstFn || Self::feature_gate(item.tcx).unwrap()
}
fn feature_gate(tcx: TyCtxt<'_>) -> Option<bool> {

19
src/librustc_mir/transform/check_consts/qualifs.rs
View File

@ -5,8 +5,7 @@ use rustc::mir::interpret::ConstValue;
use rustc::ty::{self, Ty};
use syntax_pos::DUMMY_SP;
use super::Item as ConstCx;
use super::validation::Mode;
use super::{ConstKind, Item as ConstCx};
#[derive(Clone, Copy)]
pub struct QualifSet(u8);
@ -236,13 +235,17 @@ impl Qualif for HasMutInterior {
// mutably without consequences.
match ty.kind {
// Inside a `static mut`, &mut [...] is also allowed.
ty::Array(..) | ty::Slice(_) if cx.mode == Mode::StaticMut => {},
| ty::Array(..)
| ty::Slice(_)
if cx.const_kind == Some(ConstKind::StaticMut)
=> {},
// FIXME(eddyb) the `cx.for_promotion` condition
// seems unnecessary, given that this is merely a ZST.
ty::Array(_, len)
if len.try_eval_usize(cx.tcx, cx.param_env) == Some(0)
&& cx.for_promotion => {},
// FIXME(eddyb): We only return false for `&mut []` outside a const
// context which seems unnecessary given that this is merely a ZST.
| ty::Array(_, len)
if len.try_eval_usize(cx.tcx, cx.param_env) == Some(0)
&& cx.const_kind == None
=> {},
_ => return true,
}

153
src/librustc_mir/transform/check_consts/resolver.rs
View File

@ -1,21 +1,18 @@
//! Propagate `Qualif`s between locals and query the results.
//!
//! This also contains the dataflow analysis used to track `Qualif`s on complex control-flow
//! graphs.
//! This contains the dataflow analysis used to track `Qualif`s on complex control-flow graphs.
use rustc::mir::visit::Visitor;
use rustc::mir::{self, BasicBlock, Local, Location};
use rustc_index::bit_set::BitSet;
use std::cell::RefCell;
use std::marker::PhantomData;
use crate::dataflow::{self as old_dataflow, generic as dataflow};
use super::{Item, Qualif};
use self::old_dataflow::IndirectlyMutableLocals;
/// A `Visitor` that propagates qualifs between locals. This defines the transfer function of
/// `FlowSensitiveAnalysis` as well as the logic underlying `TempPromotionResolver`.
/// `FlowSensitiveAnalysis`.
///
/// This transfer does nothing when encountering an indirect assignment. Consumers should rely on
/// the `IndirectlyMutableLocals` dataflow pass to see if a `Local` may have become qualified via
@ -147,145 +144,6 @@ where
}
}
/// Types that can compute the qualifs of each local at each location in a `mir::Body`.
///
/// Code that wishes to use a `QualifResolver` must call `visit_{statement,terminator}` for each
/// statement or terminator, processing blocks in reverse post-order beginning from the
/// `START_BLOCK`. Calling code may optionally call `get` after visiting each statement or
/// terminator to query the qualification state immediately before that statement or terminator.
///
/// These conditions are much more restrictive than woud be required by `FlowSensitiveResolver`
/// alone. This is to allow a linear, on-demand `TempPromotionResolver` that can operate
/// efficiently on simple CFGs.
pub trait QualifResolver<Q> {
/// Get the qualifs of each local at the last location visited.
///
/// This takes `&mut self` so qualifs can be computed lazily.
fn get(&mut self) -> &BitSet<Local>;
/// A convenience method for `self.get().contains(local)`.
fn contains(&mut self, local: Local) -> bool {
self.get().contains(local)
}
/// Resets the resolver to the `START_BLOCK`. This allows a resolver to be reused
/// for multiple passes over a `mir::Body`.
fn reset(&mut self);
}
pub type IndirectlyMutableResults<'mir, 'tcx> =
old_dataflow::DataflowResultsCursor<'mir, 'tcx, IndirectlyMutableLocals<'mir, 'tcx>>;
/// A resolver for qualifs that works on arbitrarily complex CFGs.
///
/// As soon as a `Local` becomes writable through a reference (as determined by the
/// `IndirectlyMutableLocals` dataflow pass), we must assume that it takes on all other qualifs
/// possible for its type. This is because no effort is made to track qualifs across indirect
/// assignments (e.g. `*p = x` or calls to opaque functions).
///
/// It is possible to be more precise here by waiting until an indirect assignment actually occurs
/// before marking a borrowed `Local` as qualified.
pub struct FlowSensitiveResolver<'a, 'mir, 'tcx, Q>
where
Q: Qualif,
{
location: Location,
indirectly_mutable_locals: &'a RefCell<IndirectlyMutableResults<'mir, 'tcx>>,
cursor: dataflow::ResultsCursor<'mir, 'tcx, FlowSensitiveAnalysis<'a, 'mir, 'tcx, Q>>,
qualifs_per_local: BitSet<Local>,
/// The value of `Q::in_any_value_of_ty` for each local.
qualifs_in_any_value_of_ty: BitSet<Local>,
}
impl<Q> FlowSensitiveResolver<'a, 'mir, 'tcx, Q>
where
Q: Qualif,
{
pub fn new(
_: Q,
item: &'a Item<'mir, 'tcx>,
indirectly_mutable_locals: &'a RefCell<IndirectlyMutableResults<'mir, 'tcx>>,
dead_unwinds: &BitSet<BasicBlock>,
) -> Self {
let analysis = FlowSensitiveAnalysis {
item,
_qualif: PhantomData,
};
let results =
dataflow::Engine::new(item.tcx, item.body, item.def_id, dead_unwinds, analysis)
.iterate_to_fixpoint();
let cursor = dataflow::ResultsCursor::new(item.body, results);
let mut qualifs_in_any_value_of_ty = BitSet::new_empty(item.body.local_decls.len());
for (local, decl) in item.body.local_decls.iter_enumerated() {
if Q::in_any_value_of_ty(item, decl.ty) {
qualifs_in_any_value_of_ty.insert(local);
}
}
FlowSensitiveResolver {
cursor,
indirectly_mutable_locals,
qualifs_per_local: BitSet::new_empty(item.body.local_decls.len()),
qualifs_in_any_value_of_ty,
location: Location { block: mir::START_BLOCK, statement_index: 0 },
}
}
}
impl<Q> Visitor<'tcx> for FlowSensitiveResolver<'_, '_, 'tcx, Q>
where
Q: Qualif
{
fn visit_statement(&mut self, _: &mir::Statement<'tcx>, location: Location) {
self.location = location;
}
fn visit_terminator(&mut self, _: &mir::Terminator<'tcx>, location: Location) {
self.location = location;
}
}
impl<Q> QualifResolver<Q> for FlowSensitiveResolver<'_, '_, '_, Q>
where
Q: Qualif
{
fn get(&mut self) -> &BitSet<Local> {
let mut indirectly_mutable_locals = self.indirectly_mutable_locals.borrow_mut();
indirectly_mutable_locals.seek(self.location);
self.cursor.seek_before(self.location);
self.qualifs_per_local.overwrite(indirectly_mutable_locals.get());
self.qualifs_per_local.union(self.cursor.get());
self.qualifs_per_local.intersect(&self.qualifs_in_any_value_of_ty);
&self.qualifs_per_local
}
fn contains(&mut self, local: Local) -> bool {
// No need to update the cursor if we know that `Local` cannot possibly be qualified.
if !self.qualifs_in_any_value_of_ty.contains(local) {
return false;
}
// Otherwise, return `true` if this local is qualified or was indirectly mutable at any
// point before this statement.
self.cursor.seek_before(self.location);
if self.cursor.get().contains(local) {
return true;
}
let mut indirectly_mutable_locals = self.indirectly_mutable_locals.borrow_mut();
indirectly_mutable_locals.seek(self.location);
indirectly_mutable_locals.get().contains(local)
}
fn reset(&mut self) {
self.location = Location { block: mir::START_BLOCK, statement_index: 0 };
}
}
/// The dataflow analysis used to propagate qualifs on arbitrary CFGs.
pub(super) struct FlowSensitiveAnalysis<'a, 'mir, 'tcx, Q> {
item: &'a Item<'mir, 'tcx>,
@ -296,6 +154,13 @@ impl<'a, 'mir, 'tcx, Q> FlowSensitiveAnalysis<'a, 'mir, 'tcx, Q>
where
Q: Qualif,
{
pub(super) fn new(_: Q, item: &'a Item<'mir, 'tcx>) -> Self {
FlowSensitiveAnalysis {
item,
_qualif: PhantomData,
}
}
fn transfer_function(
&self,
state: &'a mut BitSet<Local>,

213
src/librustc_mir/transform/check_consts/validation.rs
View File

@ -1,24 +1,23 @@
//! The `Visitor` responsible for actually checking a `mir::Body` for invalid operations.
use rustc::hir::{self, def_id::DefId};
use rustc::mir::visit::{PlaceContext, Visitor, MutatingUseContext, NonMutatingUseContext};
use rustc::mir::*;
use rustc::ty::cast::CastTy;
use rustc::ty::{self, TyCtxt};
use rustc::ty;
use rustc_index::bit_set::BitSet;
use rustc_target::spec::abi::Abi;
use syntax::symbol::sym;
use syntax_pos::Span;
use std::cell::RefCell;
use std::fmt;
use std::ops::Deref;
use crate::dataflow as old_dataflow;
use super::{Item, Qualif, is_lang_panic_fn};
use super::resolver::{FlowSensitiveResolver, IndirectlyMutableResults, QualifResolver};
use super::qualifs::{HasMutInterior, NeedsDrop};
use crate::dataflow::{self as old_dataflow, generic as dataflow};
use self::old_dataflow::IndirectlyMutableLocals;
use super::ops::{self, NonConstOp};
use super::qualifs::{HasMutInterior, NeedsDrop};
use super::resolver::FlowSensitiveAnalysis;
use super::{ConstKind, Item, Qualif, is_lang_panic_fn};
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum CheckOpResult {
@ -27,73 +26,75 @@ pub enum CheckOpResult {
Allowed,
}
/// What kind of item we are in.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum Mode {
/// A `static` item.
Static,
/// A `static mut` item.
StaticMut,
/// A `const fn` item.
ConstFn,
/// A `const` item or an anonymous constant (e.g. in array lengths).
Const,
pub type IndirectlyMutableResults<'mir, 'tcx> =
old_dataflow::DataflowResultsCursor<'mir, 'tcx, IndirectlyMutableLocals<'mir, 'tcx>>;
struct QualifCursor<'a, 'mir, 'tcx, Q: Qualif> {
cursor: dataflow::ResultsCursor<'mir, 'tcx, FlowSensitiveAnalysis<'a, 'mir, 'tcx, Q>>,
in_any_value_of_ty: BitSet<Local>,
}
impl Mode {
/// Returns the validation mode for the item with the given `DefId`, or `None` if this item
/// does not require validation (e.g. a non-const `fn`).
pub fn for_item(tcx: TyCtxt<'tcx>, def_id: DefId) -> Option<Self> {
use hir::BodyOwnerKind as HirKind;
impl<Q: Qualif> QualifCursor<'a, 'mir, 'tcx, Q> {
pub fn new(
q: Q,
item: &'a Item<'mir, 'tcx>,
dead_unwinds: &BitSet<BasicBlock>,
) -> Self {
let analysis = FlowSensitiveAnalysis::new(q, item);
let results =
dataflow::Engine::new(item.tcx, item.body, item.def_id, dead_unwinds, analysis)
.iterate_to_fixpoint();
let cursor = dataflow::ResultsCursor::new(item.body, results);
let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
let mode = match tcx.hir().body_owner_kind(hir_id) {
HirKind::Closure => return None,
HirKind::Fn if tcx.is_const_fn(def_id) => Mode::ConstFn,
HirKind::Fn => return None,
HirKind::Const => Mode::Const,
HirKind::Static(hir::MutImmutable) => Mode::Static,
HirKind::Static(hir::MutMutable) => Mode::StaticMut,
};
Some(mode)
}
pub fn is_static(self) -> bool {
match self {
Mode::Static | Mode::StaticMut => true,
Mode::ConstFn | Mode::Const => false,
let mut in_any_value_of_ty = BitSet::new_empty(item.body.local_decls.len());
for (local, decl) in item.body.local_decls.iter_enumerated() {
if Q::in_any_value_of_ty(item, decl.ty) {
in_any_value_of_ty.insert(local);
}
}
}
/// Returns `true` if the value returned by this item must be `Sync`.
///
/// This returns false for `StaticMut` since all accesses to one are `unsafe` anyway.
pub fn requires_sync(self) -> bool {
match self {
Mode::Static => true,
Mode::ConstFn | Mode::Const | Mode::StaticMut => false,
}
}
}
impl fmt::Display for Mode {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match *self {
Mode::Const => write!(f, "constant"),
Mode::Static | Mode::StaticMut => write!(f, "static"),
Mode::ConstFn => write!(f, "constant function"),
QualifCursor {
cursor,
in_any_value_of_ty,
}
}
}
pub struct Qualifs<'a, 'mir, 'tcx> {
has_mut_interior: FlowSensitiveResolver<'a, 'mir, 'tcx, HasMutInterior>,
needs_drop: FlowSensitiveResolver<'a, 'mir, 'tcx, NeedsDrop>,
has_mut_interior: QualifCursor<'a, 'mir, 'tcx, HasMutInterior>,
needs_drop: QualifCursor<'a, 'mir, 'tcx, NeedsDrop>,
indirectly_mutable: IndirectlyMutableResults<'mir, 'tcx>,
}
impl Qualifs<'a, 'mir, 'tcx> {
fn indirectly_mutable(&mut self, local: Local, location: Location) -> bool {
self.indirectly_mutable.seek(location);
self.indirectly_mutable.get().contains(local)
}
/// Returns `true` if `local` is `NeedsDrop` at the given `Location`.
///
/// Only updates the cursor if absolutely necessary
fn needs_drop_lazy_seek(&mut self, local: Local, location: Location) -> bool {
if !self.needs_drop.in_any_value_of_ty.contains(local) {
return false;
}
self.needs_drop.cursor.seek_before(location);
self.needs_drop.cursor.get().contains(local)
|| self.indirectly_mutable(local, location)
}
/// Returns `true` if `local` is `HasMutInterior`, but requires the `has_mut_interior` and
/// `indirectly_mutable` cursors to be updated beforehand.
fn has_mut_interior_eager_seek(&self, local: Local) -> bool {
if !self.has_mut_interior.in_any_value_of_ty.contains(local) {
return false;
}
self.has_mut_interior.cursor.get().contains(local)
|| self.indirectly_mutable.get().contains(local)
}
}
pub struct Validator<'a, 'mir, 'tcx> {
@ -128,53 +129,43 @@ impl Deref for Validator<'_, 'mir, 'tcx> {
}
}
pub fn compute_indirectly_mutable_locals<'mir, 'tcx>(
item: &Item<'mir, 'tcx>,
) -> RefCell<IndirectlyMutableResults<'mir, 'tcx>> {
let dead_unwinds = BitSet::new_empty(item.body.basic_blocks().len());
let indirectly_mutable_locals = old_dataflow::do_dataflow(
item.tcx,
item.body,
item.def_id,
&item.tcx.get_attrs(item.def_id),
&dead_unwinds,
old_dataflow::IndirectlyMutableLocals::new(item.tcx, item.body, item.param_env),
|_, local| old_dataflow::DebugFormatted::new(&local),
);
let indirectly_mutable_locals = old_dataflow::DataflowResultsCursor::new(
indirectly_mutable_locals,
item.body,
);
RefCell::new(indirectly_mutable_locals)
}
impl Validator<'a, 'mir, 'tcx> {
pub fn new(
item: &'a Item<'mir, 'tcx>,
indirectly_mutable_locals: &'a RefCell<IndirectlyMutableResults<'mir, 'tcx>>,
) -> Self {
let dead_unwinds = BitSet::new_empty(item.body.basic_blocks().len());
let needs_drop = FlowSensitiveResolver::new(
let needs_drop = QualifCursor::new(
NeedsDrop,
item,
indirectly_mutable_locals,
&dead_unwinds,
);
let has_mut_interior = FlowSensitiveResolver::new(
let has_mut_interior = QualifCursor::new(
HasMutInterior,
item,
indirectly_mutable_locals,
&dead_unwinds,
);
let indirectly_mutable = old_dataflow::do_dataflow(
item.tcx,
item.body,
item.def_id,
&item.tcx.get_attrs(item.def_id),
&dead_unwinds,
old_dataflow::IndirectlyMutableLocals::new(item.tcx, item.body, item.param_env),
|_, local| old_dataflow::DebugFormatted::new(&local),
);
let indirectly_mutable = old_dataflow::DataflowResultsCursor::new(
indirectly_mutable,
item.body,
);
let qualifs = Qualifs {
needs_drop,
has_mut_interior,
indirectly_mutable,
};
Validator {
@ -187,14 +178,6 @@ impl Validator<'a, 'mir, 'tcx> {
}
}
/// Resets the `QualifResolver`s used by this `Validator` and returns them so they can be
/// reused.
pub fn into_qualifs(mut self) -> Qualifs<'a, 'mir, 'tcx> {
self.qualifs.needs_drop.reset();
self.qualifs.has_mut_interior.reset();
self.qualifs
}
pub fn take_errors(&mut self) -> Vec<(Span, String)> {
std::mem::replace(&mut self.errors, vec![])
}
@ -343,7 +326,7 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
let is_thread_local = self.tcx.has_attr(*def_id, sym::thread_local);
if is_thread_local {
self.check_op(ops::ThreadLocalAccess);
} else if self.mode == Mode::Static && context.is_mutating_use() {
} else if self.const_kind() == ConstKind::Static && context.is_mutating_use() {
// this is not strictly necessary as miri will also bail out
// For interior mutability we can't really catch this statically as that
// goes through raw pointers and intermediate temporaries, so miri has
@ -369,10 +352,16 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
// it depends on `HasMutInterior` being set for mutable borrows as well as values with
// interior mutability.
if let Rvalue::Ref(_, kind, ref borrowed_place) = *rvalue {
let rvalue_has_mut_interior = {
let has_mut_interior = self.qualifs.has_mut_interior.get();
HasMutInterior::in_rvalue(&self.item, &|l| has_mut_interior.contains(l), rvalue)
};
// FIXME: Change the `in_*` methods to take a `FnMut` so we don't have to manually seek
// the cursors beforehand.
self.qualifs.has_mut_interior.cursor.seek_before(location);
self.qualifs.indirectly_mutable.seek(location);
let rvalue_has_mut_interior = HasMutInterior::in_rvalue(
&self.item,
&|local| self.qualifs.has_mut_interior_eager_seek(local),
rvalue,
);
if rvalue_has_mut_interior {
let is_derived_from_illegal_borrow = match borrowed_place.as_local() {
@ -467,9 +456,6 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
trace!("visit_statement: statement={:?} location={:?}", statement, location);
self.qualifs.needs_drop.visit_statement(statement, location);
self.qualifs.has_mut_interior.visit_statement(statement, location);
match statement.kind {
StatementKind::Assign(..) => {
self.super_statement(statement, location);
@ -489,15 +475,6 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
}
}
fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
trace!("visit_terminator: terminator={:?} location={:?}", terminator, location);
self.qualifs.needs_drop.visit_terminator(terminator, location);
self.qualifs.has_mut_interior.visit_terminator(terminator, location);
self.super_terminator(terminator, location);
}
fn visit_terminator_kind(&mut self, kind: &TerminatorKind<'tcx>, location: Location) {
trace!("visit_terminator_kind: kind={:?} location={:?}", kind, location);
self.super_terminator_kind(kind, location);
@ -576,7 +553,7 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
let needs_drop = if let Some(local) = dropped_place.as_local() {
// Use the span where the local was declared as the span of the drop error.
err_span = self.body.local_decls[local].source_info.span;
self.qualifs.needs_drop.contains(local)
self.qualifs.needs_drop_lazy_seek(local, location)
} else {
true
};

85
src/librustc_mir/transform/promote_consts.rs
View File

@ -12,7 +12,6 @@
//! initialization and can otherwise silence errors, if
//! move analysis runs after promotion on broken MIR.
use rustc::hir;
use rustc::hir::def_id::DefId;
use rustc::mir::*;
use rustc::mir::interpret::ConstValue;
@ -30,7 +29,7 @@ use rustc_target::spec::abi::Abi;
use std::{iter, mem, usize};
use crate::transform::check_consts::{qualifs, Item as ConstCx};
use crate::transform::check_consts::{qualifs, Item, ConstKind, is_lang_panic_fn};
/// State of a temporary during collection and promotion.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
@ -224,18 +223,13 @@ pub fn collect_temps_and_candidates(
(collector.temps, collector.candidates)
}
/// Checks whether locals that appear in a promotion context (`Candidate`) are actually promotable.
///
/// This wraps an `Item`, and has access to all fields of that `Item` via `Deref` coercion.
struct Validator<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
body: &'a Body<'tcx>,
is_static: bool,
is_static_mut: bool,
is_non_const_fn: bool,
item: Item<'a, 'tcx>,
temps: &'a IndexVec<Local, TempState>,
// FIXME(eddyb) deduplicate the data in this vs other fields.
const_cx: ConstCx<'a, 'tcx>,
/// Explicit promotion happens e.g. for constant arguments declared via
/// `rustc_args_required_const`.
/// Implicit promotion has almost the same rules, except that disallows `const fn`
@ -245,14 +239,17 @@ struct Validator<'a, 'tcx> {
explicit: bool,
}
impl std::ops::Deref for Validator<'a, 'tcx> {
type Target = Item<'a, 'tcx>;
fn deref(&self) -> &Self::Target {
&self.item
}
}
struct Unpromotable;
impl<'tcx> Validator<'_, 'tcx> {
fn is_const_panic_fn(&self, def_id: DefId) -> bool {
Some(def_id) == self.tcx.lang_items().panic_fn() ||
Some(def_id) == self.tcx.lang_items().begin_panic_fn()
}
fn validate_candidate(&self, candidate: Candidate) -> Result<(), Unpromotable> {
match candidate {
Candidate::Ref(loc) => {
@ -317,13 +314,14 @@ impl<'tcx> Validator<'_, 'tcx> {
if self.qualif_local::<qualifs::NeedsDrop>(base) {
return Err(Unpromotable);
}
if let BorrowKind::Mut { .. } = kind {
let ty = place.ty(self.body, self.tcx).ty;
// In theory, any zero-sized value could be borrowed
// mutably without consequences. However, only &mut []
// is allowed right now, and only in functions.
if self.is_static_mut {
if self.const_kind == Some(ConstKind::StaticMut) {
// Inside a `static mut`, &mut [...] is also allowed.
match ty.kind {
ty::Array(..) | ty::Slice(_) => {}
@ -333,7 +331,7 @@ impl<'tcx> Validator<'_, 'tcx> {
// FIXME(eddyb) the `self.is_non_const_fn` condition
// seems unnecessary, given that this is merely a ZST.
match len.try_eval_usize(self.tcx, self.param_env) {
Some(0) if self.is_non_const_fn => {},
Some(0) if self.const_kind.is_none() => {},
_ => return Err(Unpromotable),
}
} else {
@ -386,7 +384,7 @@ impl<'tcx> Validator<'_, 'tcx> {
let statement = &self.body[loc.block].statements[loc.statement_index];
match &statement.kind {
StatementKind::Assign(box(_, rhs)) => {
Q::in_rvalue(&self.const_cx, per_local, rhs)
Q::in_rvalue(&self.item, per_local, rhs)
}
_ => {
span_bug!(statement.source_info.span, "{:?} is not an assignment",
@ -398,7 +396,7 @@ impl<'tcx> Validator<'_, 'tcx> {
match &terminator.kind {
TerminatorKind::Call { func, args, .. } => {
let return_ty = self.body.local_decls[local].ty;
Q::in_call(&self.const_cx, per_local, func, args, return_ty)
Q::in_call(&self.item, per_local, func, args, return_ty)
}
kind => {
span_bug!(terminator.source_info.span, "{:?} not promotable", kind);
@ -462,8 +460,8 @@ impl<'tcx> Validator<'_, 'tcx> {
} => {
// Only allow statics (not consts) to refer to other statics.
// FIXME(eddyb) does this matter at all for promotion?
let allowed = self.is_static || self.is_static_mut;
if !allowed {
let is_static = self.const_kind.map_or(false, |k| k.is_static());
if !is_static {
return Err(Unpromotable);
}
@ -490,7 +488,7 @@ impl<'tcx> Validator<'_, 'tcx> {
}
ProjectionElem::Field(..) => {
if self.is_non_const_fn {
if self.const_kind.is_none() {
let base_ty =
Place::ty_from(place.base, proj_base, self.body, self.tcx).ty;
if let Some(def) = base_ty.ty_adt_def() {
@ -545,7 +543,7 @@ impl<'tcx> Validator<'_, 'tcx> {
fn validate_rvalue(&self, rvalue: &Rvalue<'tcx>) -> Result<(), Unpromotable> {
match *rvalue {
Rvalue::Cast(CastKind::Misc, ref operand, cast_ty) if self.is_non_const_fn => {
Rvalue::Cast(CastKind::Misc, ref operand, cast_ty) if self.const_kind.is_none() => {
let operand_ty = operand.ty(self.body, self.tcx);
let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast");
let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
@ -559,7 +557,7 @@ impl<'tcx> Validator<'_, 'tcx> {
}
}
Rvalue::BinaryOp(op, ref lhs, _) if self.is_non_const_fn => {
Rvalue::BinaryOp(op, ref lhs, _) if self.const_kind.is_none() => {
if let ty::RawPtr(_) | ty::FnPtr(..) = lhs.ty(self.body, self.tcx).kind {
assert!(op == BinOp::Eq || op == BinOp::Ne ||
op == BinOp::Le || op == BinOp::Lt ||
@ -600,17 +598,17 @@ impl<'tcx> Validator<'_, 'tcx> {
// In theory, any zero-sized value could be borrowed
// mutably without consequences. However, only &mut []
// is allowed right now, and only in functions.
if self.is_static_mut {
if self.const_kind == Some(ConstKind::StaticMut) {
// Inside a `static mut`, &mut [...] is also allowed.
match ty.kind {
ty::Array(..) | ty::Slice(_) => {}
_ => return Err(Unpromotable),
}
} else if let ty::Array(_, len) = ty.kind {
// FIXME(eddyb) the `self.is_non_const_fn` condition
// seems unnecessary, given that this is merely a ZST.
// FIXME(eddyb): We only return `Unpromotable` for `&mut []` inside a
// const context which seems unnecessary given that this is merely a ZST.
match len.try_eval_usize(self.tcx, self.param_env) {
Some(0) if self.is_non_const_fn => {},
Some(0) if self.const_kind.is_none() => {},
_ => return Err(Unpromotable),
}
} else {
@ -683,7 +681,7 @@ impl<'tcx> Validator<'_, 'tcx> {
) -> Result<(), Unpromotable> {
let fn_ty = callee.ty(self.body, self.tcx);
if !self.explicit && self.is_non_const_fn {
if !self.explicit && self.const_kind.is_none() {
if let ty::FnDef(def_id, _) = fn_ty.kind {
// Never promote runtime `const fn` calls of
// functions without `#[rustc_promotable]`.
@ -697,7 +695,7 @@ impl<'tcx> Validator<'_, 'tcx> {
ty::FnDef(def_id, _) => {
self.tcx.is_const_fn(def_id) ||
self.tcx.is_unstable_const_fn(def_id).is_some() ||
self.is_const_panic_fn(def_id)
is_lang_panic_fn(self.tcx, self.def_id)
}
_ => false,
};
@ -714,6 +712,7 @@ impl<'tcx> Validator<'_, 'tcx> {
}
}
// FIXME(eddyb) remove the differences for promotability in `static`, `const`, `const fn`.
pub fn validate_candidates(
tcx: TyCtxt<'tcx>,
body: &Body<'tcx>,
@ -722,33 +721,11 @@ pub fn validate_candidates(
candidates: &[Candidate],
) -> Vec<Candidate> {
let mut validator = Validator {
tcx,
param_env: tcx.param_env(def_id),
body,
is_static: false,
is_static_mut: false,
is_non_const_fn: false,
item: Item::new(tcx, def_id, body),
temps,
const_cx: ConstCx::for_promotion(tcx, def_id, body),
explicit: false,
};
// FIXME(eddyb) remove the distinctions that make this necessary.
let id = tcx.hir().as_local_hir_id(def_id).unwrap();
match tcx.hir().body_owner_kind(id) {
hir::BodyOwnerKind::Closure => validator.is_non_const_fn = true,
hir::BodyOwnerKind::Fn => {
if !tcx.is_const_fn(def_id) {
validator.is_non_const_fn = true;
}
},
hir::BodyOwnerKind::Static(hir::MutImmutable) => validator.is_static = true,
hir::BodyOwnerKind::Static(hir::MutMutable) => validator.is_static_mut = true,
_ => {}
}
candidates.iter().copied().filter(|&candidate| {
validator.explicit = match candidate {
Candidate::Ref(_) |

3
src/librustc_mir/transform/qualify_consts.rs
View File

@ -968,8 +968,7 @@ impl<'a, 'tcx> Checker<'a, 'tcx> {
}
let item = new_checker::Item::new(self.tcx, self.def_id, self.body);
let mut_borrowed_locals = new_checker::validation::compute_indirectly_mutable_locals(&item);
let mut validator = new_checker::validation::Validator::new(&item, &mut_borrowed_locals);
let mut validator = new_checker::validation::Validator::new(&item);
validator.suppress_errors = !use_new_validator;
self.suppress_errors = use_new_validator;