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rustc_mir: split off some qualify_consts::Checker fields into a State…
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… struct.
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@eddyb
eddyb committed Feb 14, 2019
1 parent a5e4d1a commit 732a2dc
Showing 1 changed file with 73 additions and 61 deletions.
134 changes: 73 additions & 61 deletions src/librustc_mir/transform/qualify_consts.rs
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Expand Up @@ -94,18 +94,31 @@ impl fmt::Display for Mode {
}
}

struct Checker<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
struct State {
local_qualif: IndexVec<Local, Option<Qualif>>,

qualif: Qualif,
}

impl State {
/// Add the given qualification to self.qualif.
fn add(&mut self, qualif: Qualif) {
self.qualif = self.qualif | qualif;
}
}

struct Checker<'a, 'gcx, 'tcx> {
tcx: TyCtxt<'a, 'gcx, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
mode: Mode,
span: Span,
def_id: DefId,
mir: &'a Mir<'tcx>,
rpo: ReversePostorder<'a, 'tcx>,
tcx: TyCtxt<'a, 'gcx, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
local_qualif: IndexVec<Local, Option<Qualif>>,
qualif: Qualif,

state: State,
temp_promotion_state: IndexVec<Local, TempState>,
promotion_candidates: Vec<Candidate>
promotion_candidates: Vec<Candidate>,
}

macro_rules! unleash_miri {
Expand Down Expand Up @@ -145,8 +158,10 @@ impl<'a, 'tcx> Checker<'a, 'tcx, 'tcx> {
rpo,
tcx,
param_env,
local_qualif,
qualif: Qualif::empty(),
state: State {
local_qualif,
qualif: Qualif::empty(),
},
temp_promotion_state: temps,
promotion_candidates: vec![]
}
Expand All @@ -157,7 +172,7 @@ impl<'a, 'tcx> Checker<'a, 'tcx, 'tcx> {
// slightly pointless (even with feature-gating).
fn not_const(&mut self) {
unleash_miri!(self);
self.add(Qualif::NOT_CONST);
self.state.add(Qualif::NOT_CONST);
if self.mode != Mode::Fn {
let mut err = struct_span_err!(
self.tcx.sess,
Expand All @@ -176,31 +191,26 @@ impl<'a, 'tcx> Checker<'a, 'tcx, 'tcx> {
}
}

/// Adds the given qualification to `self.qualif`.
fn add(&mut self, qualif: Qualif) {
self.qualif = self.qualif | qualif;
}

/// Adds the given type's qualification to `self.qualif`.
/// Adds the given type's qualification to self.state.qualif.
fn add_type(&mut self, ty: Ty<'tcx>) {
self.add(Qualif::MUTABLE_INTERIOR | Qualif::NEEDS_DROP);
self.qualif.restrict(ty, self.tcx, self.param_env);
self.state.add(Qualif::MUTABLE_INTERIOR | Qualif::NEEDS_DROP);
self.state.qualif.restrict(ty, self.tcx, self.param_env);
}

/// Within the provided closure, `self.qualif` will start
/// Within the provided closure, `self.state.qualif` will start
/// out empty, and its value after the closure returns will
/// be combined with the value before the call to nest.
fn nest<F: FnOnce(&mut Self)>(&mut self, f: F) {
let original = self.qualif;
self.qualif = Qualif::empty();
let original = self.state.qualif;
self.state.qualif = Qualif::empty();
f(self);
self.add(original);
self.state.add(original);
}

/// Assign the current qualification to the given destination.
fn assign(&mut self, dest: &Place<'tcx>, location: Location) {
trace!("assign: {:?}", dest);
let qualif = self.qualif;
let qualif = self.state.qualif;
let span = self.span;
let store = |slot: &mut Option<Qualif>| {
if slot.is_some() {
Expand All @@ -215,7 +225,7 @@ impl<'a, 'tcx> Checker<'a, 'tcx, 'tcx> {
if self.mir.local_kind(index) == LocalKind::Temp
&& self.temp_promotion_state[index].is_promotable() {
debug!("store to promotable temp {:?} ({:?})", index, qualif);
store(&mut self.local_qualif[index]);
store(&mut self.state.local_qualif[index]);
}
}
return;
Expand Down Expand Up @@ -253,14 +263,14 @@ impl<'a, 'tcx> Checker<'a, 'tcx, 'tcx> {
}
};
debug!("store to var {:?}", index);
match &mut self.local_qualif[index] {
match &mut self.state.local_qualif[index] {
// this is overly restrictive, because even full assignments do not clear the qualif
// While we could special case full assignments, this would be inconsistent with
// aggregates where we overwrite all fields via assignments, which would not get
// that feature.
Some(ref mut qualif) => *qualif = *qualif | self.qualif,
Some(ref mut qualif) => *qualif = *qualif | self.state.qualif,
// insert new qualification
qualif @ None => *qualif = Some(self.qualif),
qualif @ None => *qualif = Some(self.state.qualif),
}
}

Expand Down Expand Up @@ -317,12 +327,12 @@ impl<'a, 'tcx> Checker<'a, 'tcx, 'tcx> {
}
}

self.qualif = self.local_qualif[RETURN_PLACE].unwrap_or(Qualif::NOT_CONST);
self.state.qualif = self.state.local_qualif[RETURN_PLACE].unwrap_or(Qualif::NOT_CONST);

// Account for errors in consts by using the
// conservative type qualification instead.
if self.qualif.intersects(Qualif::CONST_ERROR) {
self.qualif = Qualif::empty();
if self.state.qualif.intersects(Qualif::CONST_ERROR) {
self.state.qualif = Qualif::empty();
let return_ty = mir.return_ty();
self.add_type(return_ty);
}
Expand All @@ -346,7 +356,7 @@ impl<'a, 'tcx> Checker<'a, 'tcx, 'tcx> {
}
}

(self.qualif, Lrc::new(promoted_temps))
(self.state.qualif, Lrc::new(promoted_temps))
}

fn is_const_panic_fn(&self, def_id: DefId) -> bool {
Expand All @@ -355,7 +365,7 @@ impl<'a, 'tcx> Checker<'a, 'tcx, 'tcx> {
}
}

/// Accumulates an Rvalue or Call's effects in self.qualif.
/// Accumulates an Rvalue or Call's effects in self.state.qualif.
/// For functions (constant or not), it also records
/// candidates for promotion in promotion_candidates.
impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
Expand All @@ -370,22 +380,22 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
self.not_const();
}
LocalKind::Var if self.mode == Mode::Fn => {
self.add(Qualif::NOT_CONST);
self.state.add(Qualif::NOT_CONST);
}
LocalKind::Var |
LocalKind::Arg |
LocalKind::Temp => {
if let LocalKind::Arg = kind {
self.add(Qualif::FN_ARGUMENT);
self.state.add(Qualif::FN_ARGUMENT);
}

if !self.temp_promotion_state[local].is_promotable() {
debug!("visit_local: (not promotable) local={:?}", local);
self.add(Qualif::NOT_PROMOTABLE);
self.state.add(Qualif::NOT_PROMOTABLE);
}

if let Some(qualif) = self.local_qualif[local] {
self.add(qualif);
if let Some(qualif) = self.state.local_qualif[local] {
self.state.add(qualif);
} else {
self.not_const();
}
Expand All @@ -411,7 +421,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
"thread-local statics cannot be \
accessed at compile-time");
}
self.add(Qualif::NOT_CONST);
self.state.add(Qualif::NOT_CONST);
return;
}

Expand All @@ -430,7 +440,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
return;
}
unleash_miri!(self);
self.add(Qualif::NOT_CONST);
self.state.add(Qualif::NOT_CONST);

if self.mode != Mode::Fn {
let mut err = struct_span_err!(self.tcx.sess, self.span, E0013,
Expand Down Expand Up @@ -458,7 +468,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
this.not_const()
} else {
// just make sure this doesn't get promoted
this.add(Qualif::NOT_CONST);
this.state.add(Qualif::NOT_CONST);
}
let base_ty = proj.base.ty(this.mir, this.tcx).to_ty(this.tcx);
match this.mode {
Expand Down Expand Up @@ -508,7 +518,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
}

let ty = place.ty(this.mir, this.tcx).to_ty(this.tcx);
this.qualif.restrict(ty, this.tcx, this.param_env);
this.state.qualif.restrict(ty, this.tcx, this.param_env);
}

ProjectionElem::Downcast(..) => {
Expand All @@ -529,7 +539,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
Operand::Move(_) => {
// Mark the consumed locals to indicate later drops are noops.
if let Operand::Move(Place::Local(local)) = *operand {
self.local_qualif[local] = self.local_qualif[local].map(|q|
self.state.local_qualif[local] = self.state.local_qualif[local].map(|q|
q - Qualif::NEEDS_DROP
);
}
Expand All @@ -543,12 +553,12 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
let (bits, _) = self.tcx.at(constant.span).mir_const_qualif(*def_id);

let qualif = Qualif::from_bits(bits).expect("invalid mir_const_qualif");
self.add(qualif);
self.state.add(qualif);

// Just in case the type is more specific than
// the definition, e.g., impl associated const
// with type parameters, take it into account.
self.qualif.restrict(constant.ty, self.tcx, self.param_env);
self.state.qualif.restrict(constant.ty, self.tcx, self.param_env);
}
}
}
Expand Down Expand Up @@ -630,7 +640,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {

if forbidden_mut {
unleash_miri!(self);
self.add(Qualif::NOT_CONST);
self.state.add(Qualif::NOT_CONST);
if self.mode != Mode::Fn {
let mut err = struct_span_err!(self.tcx.sess, self.span, E0017,
"references in {}s may only refer \
Expand All @@ -654,11 +664,11 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
// Constants cannot be borrowed if they contain interior mutability as
// it means that our "silent insertion of statics" could change
// initializer values (very bad).
if self.qualif.contains(Qualif::MUTABLE_INTERIOR) {
if self.state.qualif.contains(Qualif::MUTABLE_INTERIOR) {
// A reference of a MUTABLE_INTERIOR place is instead
// NOT_CONST (see `if forbidden_mut` below), to avoid
// duplicate errors (from reborrowing, for example).
self.qualif = self.qualif - Qualif::MUTABLE_INTERIOR;
self.state.qualif = self.state.qualif - Qualif::MUTABLE_INTERIOR;
if self.mode != Mode::Fn {
span_err!(self.tcx.sess, self.span, E0492,
"cannot borrow a constant which may contain \
Expand All @@ -673,7 +683,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
debug!("visit_rvalue: forbidden_mut={:?}", forbidden_mut);
if forbidden_mut {
unleash_miri!(self);
self.add(Qualif::NOT_CONST);
self.state.add(Qualif::NOT_CONST);
} else {
// We might have a candidate for promotion.
let candidate = Candidate::Ref(location);
Expand All @@ -689,7 +699,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
if let Place::Local(local) = *place {
if self.mir.local_kind(local) == LocalKind::Temp {
debug!("visit_rvalue: local={:?}", local);
if let Some(qualif) = self.local_qualif[local] {
if let Some(qualif) = self.state.local_qualif[local] {
// `forbidden_mut` is false, so we can safely ignore
// `MUTABLE_INTERIOR` from the local's qualifications.
// This allows borrowing fields which don't have
Expand All @@ -716,7 +726,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
unleash_miri!(self);
if let Mode::Fn = self.mode {
// in normal functions, mark such casts as not promotable
self.add(Qualif::NOT_CONST);
self.state.add(Qualif::NOT_CONST);
} else if !self.tcx.features().const_raw_ptr_to_usize_cast {
// in const fn and constants require the feature gate
// FIXME: make it unsafe inside const fn and constants
Expand Down Expand Up @@ -744,7 +754,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
unleash_miri!(self);
if let Mode::Fn = self.mode {
// raw pointer operations are not allowed inside promoteds
self.add(Qualif::NOT_CONST);
self.state.add(Qualif::NOT_CONST);
} else if !self.tcx.features().const_compare_raw_pointers {
// require the feature gate inside constants and const fn
// FIXME: make it unsafe to use these operations
Expand All @@ -761,7 +771,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {

Rvalue::NullaryOp(NullOp::Box, _) => {
unleash_miri!(self);
self.add(Qualif::NOT_CONST);
self.state.add(Qualif::NOT_CONST);
if self.mode != Mode::Fn {
let mut err = struct_span_err!(self.tcx.sess, self.span, E0010,
"allocations are not allowed in {}s", self.mode);
Expand All @@ -781,13 +791,13 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
Rvalue::Aggregate(ref kind, _) => {
if let AggregateKind::Adt(def, ..) = **kind {
if def.has_dtor(self.tcx) {
self.add(Qualif::NEEDS_DROP);
self.state.add(Qualif::NEEDS_DROP);
}

if Some(def.did) == self.tcx.lang_items().unsafe_cell_type() {
let ty = rvalue.ty(self.mir, self.tcx);
self.add_type(ty);
assert!(self.qualif.contains(Qualif::MUTABLE_INTERIOR));
assert!(self.state.qualif.contains(Qualif::MUTABLE_INTERIOR));
}
}
}
Expand Down Expand Up @@ -983,7 +993,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
}
let candidate = Candidate::Argument { bb, index: i };
if is_shuffle && i == 2 {
if this.qualif.is_empty() {
if this.state.qualif.is_empty() {
debug!("visit_terminator_kind: candidate={:?}", candidate);
this.promotion_candidates.push(candidate);
} else {
Expand All @@ -1010,7 +1020,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
// which happens even without the user requesting it.
// We can error out with a hard error if the argument is not
// constant here.
if (this.qualif - Qualif::NOT_PROMOTABLE).is_empty() {
if (this.state.qualif - Qualif::NOT_PROMOTABLE).is_empty() {
debug!("visit_terminator_kind: candidate={:?}", candidate);
this.promotion_candidates.push(candidate);
} else {
Expand All @@ -1023,7 +1033,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {

// non-const fn calls
if !is_const_fn {
self.qualif = Qualif::NOT_CONST;
self.state.qualif = Qualif::NOT_CONST;
if self.mode != Mode::Fn {
self.tcx.sess.delay_span_bug(
self.span,
Expand All @@ -1034,16 +1044,16 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {

if let Some((ref dest, _)) = *destination {
// Avoid propagating irrelevant callee/argument qualifications.
if self.qualif.intersects(Qualif::CONST_ERROR) {
self.qualif = Qualif::NOT_CONST;
if self.state.qualif.intersects(Qualif::CONST_ERROR) {
self.state.qualif = Qualif::NOT_CONST;
} else {
// Be conservative about the returned value of a const fn.
let tcx = self.tcx;
let ty = dest.ty(self.mir, tcx).to_ty(tcx);
if is_const_fn && !is_promotable_const_fn && self.mode == Mode::Fn {
self.qualif = Qualif::NOT_PROMOTABLE;
self.state.qualif = Qualif::NOT_PROMOTABLE;
} else {
self.qualif = Qualif::empty();
self.state.qualif = Qualif::empty();
}
self.add_type(ty);
}
Expand All @@ -1058,7 +1068,9 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx, 'tcx> {
// HACK(eddyb): emulate a bit of dataflow analysis,
// conservatively, that drop elaboration will do.
let needs_drop = if let Place::Local(local) = *place {
if self.local_qualif[local].map_or(true, |q| q.contains(Qualif::NEEDS_DROP)) {
let local_needs_drop = self.state.local_qualif[local]
.map_or(true, |q| q.contains(Qualif::NEEDS_DROP));
if local_needs_drop {
Some(self.mir.local_decls[local].source_info.span)
} else {
None
Expand Down

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