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librustc: Introduce a "quick reject" mechanism to quickly throw out #17995

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librustc: Introduce a "quick reject" mechanism to quickly throw out #17995

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4 changes: 2 additions & 2 deletions src/librustc/driver/config.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -101,7 +101,7 @@ pub struct Options {
/// An optional name to use as the crate for std during std injection,
/// written `extern crate std = "name"`. Default to "std". Used by
/// out-of-tree drivers.
pub alt_std_name: Option<String>
pub alt_std_name: Option<String>,
}

/// Some reasonable defaults
Expand Down Expand Up @@ -841,7 +841,7 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
color: color,
externs: externs,
crate_name: crate_name,
alt_std_name: None
alt_std_name: None,
}
}

Expand Down
190 changes: 190 additions & 0 deletions src/librustc/middle/ty.rs
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Expand Up @@ -586,6 +586,11 @@ pub struct ctxt<'tcx> {

/// Caches the representation hints for struct definitions.
pub repr_hint_cache: RefCell<DefIdMap<Rc<Vec<attr::ReprAttr>>>>,

pub overloaded_operator_filter:
RefCell<HashMap<SimplifiedType,OverloadedOperatorFilter>>,
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This should use FnvHashMap. I wonder if there are other places in the compiler where randomized HashMap's have been used, and which are causing non-determinism.


pub smart_pointers: RefCell<DefIdSet>,
}

pub enum tbox_flag {
Expand Down Expand Up @@ -1537,6 +1542,8 @@ pub fn mk_ctxt<'tcx>(s: Session,
trait_associated_types: RefCell::new(DefIdMap::new()),
selection_cache: traits::SelectionCache::new(),
repr_hint_cache: RefCell::new(DefIdMap::new()),
overloaded_operator_filter: RefCell::new(HashMap::new()),
smart_pointers: RefCell::new(DefIdSet::new()),
}
}

Expand Down Expand Up @@ -5598,3 +5605,186 @@ pub fn with_freevars<T>(tcx: &ty::ctxt, fid: ast::NodeId, f: |&[Freevar]| -> T)
Some(d) => f(d.as_slice())
}
}

pub enum AllowDerefableFlag<'a> {
AllowDerefable,
DisallowDerefable(&'a ParameterEnvironment),
}

#[deriving(Clone, PartialEq, Eq, Hash)]
pub enum SimplifiedType {
NilSimplifiedType,
BoolSimplifiedType,
CharSimplifiedType,
IntSimplifiedType(ast::IntTy),
UintSimplifiedType(ast::UintTy),
FloatSimplifiedType(ast::FloatTy),
EnumSimplifiedType(DefId),
StrSimplifiedType,
VecSimplifiedType,
PtrSimplifiedType,
TupleSimplifiedType(uint),
TraitSimplifiedType(DefId),
StructSimplifiedType(DefId),
UnboxedClosureSimplifiedType(DefId),
FunctionSimplifiedType(uint),
ParameterSimplifiedType,
}

impl SimplifiedType {
pub fn from_type(tcx: &ctxt,
ty: ty::t,
can_simplify_params: bool,
allow_derefable: AllowDerefableFlag)
-> Option<SimplifiedType> {
let simplified_type = match get(ty).sty {
ty_nil => Some(NilSimplifiedType),
ty_bool => Some(BoolSimplifiedType),
ty_char => Some(CharSimplifiedType),
ty_int(int_type) => Some(IntSimplifiedType(int_type)),
ty_uint(uint_type) => Some(UintSimplifiedType(uint_type)),
ty_float(float_type) => Some(FloatSimplifiedType(float_type)),
ty_enum(def_id, _) => Some(EnumSimplifiedType(def_id)),
ty_str => Some(StrSimplifiedType),
ty_trait(ref trait_info) => {
Some(TraitSimplifiedType(trait_info.def_id))
}
ty_struct(def_id, _) => {
Some(StructSimplifiedType(def_id))
}
ty_unboxed_closure(def_id, _) => {
Some(UnboxedClosureSimplifiedType(def_id))
}
ty_vec(..) => Some(VecSimplifiedType),
ty_ptr(_) => Some(PtrSimplifiedType),
ty_rptr(_, ref mt) => {
SimplifiedType::from_type(tcx,
mt.ty,
can_simplify_params,
allow_derefable)
}
ty_uniq(ref ty) => {
SimplifiedType::from_type(tcx,
*ty,
can_simplify_params,
allow_derefable)
}
ty_tup(ref tys) => Some(TupleSimplifiedType(tys.len())),
ty_closure(ref f) => {
Some(FunctionSimplifiedType(f.sig.inputs.len()))
}
ty_bare_fn(ref f) => {
Some(FunctionSimplifiedType(f.sig.inputs.len()))
}
ty_param(_) if can_simplify_params => {
Some(ParameterSimplifiedType)
}
ty_bot | ty_param(_) | ty_open(_) | ty_infer(_) | ty_err => None,
};

let simplified_type = match simplified_type {
None => return None,
Some(simplified_type) => simplified_type,
};

match allow_derefable {
AllowDerefable => {}
DisallowDerefable(param_env) => {
match tcx.overloaded_operator_filter
.borrow()
.find(&simplified_type) {
Some(ref flags) if flags.contains(
DEREF_OVERLOADED_OPERATOR_FILTER) => {
return None
}
Some(_) | None => {}
}

match get(ty).sty {
ty_param(ref param_ty) => {
let bounds = &param_env.bounds
.get(param_ty.space,
param_ty.idx)
.trait_bounds;
for bound in bounds.iter() {
let bad = Some(bound.def_id) ==
tcx.lang_items.deref_trait() ||
Some(bound.def_id) ==
tcx.lang_items.deref_mut_trait();
debug!("for param {} bound {} deref {} bad {}",
param_ty.repr(tcx),
bound.repr(tcx),
tcx.lang_items.deref_trait(),
bad);
if bad {
return None
}
}
}
_ => {}
}
}
}

Some(simplified_type)
}
}

pub enum MethodLookupKey {
SimplifiedTypeLookupKey(SimplifiedType),
SmartPointerLookupKey(ast::DefId, SimplifiedType),
}

impl MethodLookupKey {
pub fn from_type(tcx: &ctxt, ty: ty::t, param_env: &ParameterEnvironment)
-> Option<MethodLookupKey> {
match get(ty).sty {
ty_struct(def_id, ref substs) => {
if tcx.smart_pointers.borrow().contains(&def_id) {
let simplified_referent = SimplifiedType::from_type(
tcx,
*substs.types.get(subst::TypeSpace, 0),
true,
DisallowDerefable(param_env));
match simplified_referent {
None => return None,
Some(simplified_referent) => {
return Some(SmartPointerLookupKey(
def_id,
simplified_referent))
}
}
}
}
_ => {}
}

match SimplifiedType::from_type(tcx,
ty,
true,
DisallowDerefable(param_env)) {
None => None,
Some(simplified_type) => {
Some(SimplifiedTypeLookupKey(simplified_type))
}
}
}

pub fn might_match(&self, other: &SimplifiedType) -> bool {
match *self {
SimplifiedTypeLookupKey(ref this) => *this == *other,
SmartPointerLookupKey(def_id, ref this) => {
*this == *other || StructSimplifiedType(def_id) == *other
}
}
}
}

bitflags! {
flags OverloadedOperatorFilter: u8 {
const INDEX_OVERLOADED_OPERATOR_FILTER = 0x01,
const DEREF_OVERLOADED_OPERATOR_FILTER = 0x02,
const CALL_OVERLOADED_OPERATOR_FILTER = 0x04
}
}

65 changes: 60 additions & 5 deletions src/librustc/middle/typeck/check/method.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -161,7 +161,15 @@ pub fn lookup<'a, 'tcx>(
lcx.push_inherent_candidates(self_ty);
debug!("searching extension candidates");
lcx.push_bound_candidates(self_ty, None);
lcx.push_extension_candidates(expr.id);

let method_lookup_key = MethodLookupKey::from_type(fcx.tcx(),
self_ty,
&fcx.inh.param_env);
if method_lookup_key.is_none() {
debug!("couldn't simplify {}", lcx.ty_to_string(self_ty));
}
lcx.push_extension_candidates(expr.id, &method_lookup_key);

lcx.search(self_ty)
}

Expand Down Expand Up @@ -197,7 +205,14 @@ pub fn lookup_in_trait<'a, 'tcx>(
self_ty.repr(fcx.tcx()), self_expr.map(|e| e.repr(fcx.tcx())));

lcx.push_bound_candidates(self_ty, Some(trait_did));
lcx.push_extension_candidate(trait_did);

let method_lookup_key = MethodLookupKey::from_type(fcx.tcx(),
self_ty,
&fcx.inh.param_env);
if method_lookup_key.is_none() {
debug!("couldn't simplify {}", lcx.ty_to_string(self_ty));
}
lcx.push_extension_candidate(trait_did, &method_lookup_key);
lcx.search(self_ty)
}

Expand Down Expand Up @@ -484,7 +499,9 @@ impl<'a, 'tcx> LookupContext<'a, 'tcx> {
});
}

fn push_extension_candidate(&mut self, trait_did: DefId) {
fn push_extension_candidate(&mut self,
trait_did: DefId,
method_lookup_key: &Option<MethodLookupKey>) {
ty::populate_implementations_for_trait_if_necessary(self.tcx(), trait_did);

// Look for explicit implementations.
Expand All @@ -494,12 +511,16 @@ impl<'a, 'tcx> LookupContext<'a, 'tcx> {
let items = impl_items.get(impl_did);
self.push_candidates_from_impl(*impl_did,
items.as_slice(),
method_lookup_key,
true);
}
}
}

fn push_extension_candidates(&mut self, expr_id: ast::NodeId) {
fn push_extension_candidates(
&mut self,
expr_id: ast::NodeId,
method_lookup_key: &Option<MethodLookupKey>) {
// If the method being called is associated with a trait, then
// find all the impls of that trait. Each of those are
// candidates.
Expand All @@ -512,7 +533,7 @@ impl<'a, 'tcx> LookupContext<'a, 'tcx> {
} else {
"(external)".to_string()
});
self.push_extension_candidate(*trait_did);
self.push_extension_candidate(*trait_did, method_lookup_key);
}
}
}
Expand Down Expand Up @@ -775,6 +796,7 @@ impl<'a, 'tcx> LookupContext<'a, 'tcx> {
let items = impl_items.get(impl_did);
self.push_candidates_from_impl(*impl_did,
items.as_slice(),
&None,
false);
}
}
Expand All @@ -783,6 +805,7 @@ impl<'a, 'tcx> LookupContext<'a, 'tcx> {
fn push_candidates_from_impl(&mut self,
impl_did: DefId,
impl_items: &[ImplOrTraitItemId],
method_lookup_key: &Option<MethodLookupKey>,
is_extension: bool) {
let did = if self.report_statics == ReportStaticMethods {
// we only want to report each base trait once
Expand All @@ -798,6 +821,38 @@ impl<'a, 'tcx> LookupContext<'a, 'tcx> {
return; // already visited
}

// See if we can quickly reject...
match *method_lookup_key {
Some(ref method_lookup_key) => {
let impl_type = ty::lookup_item_type(self.tcx(), impl_did);
let simplified_impl_type =
SimplifiedType::from_type(self.tcx(),
impl_type.ty,
false,
ty::AllowDerefable);
match simplified_impl_type {
Some(ref simplified_impl_type) => {
if !method_lookup_key.might_match(
simplified_impl_type) {
debug!("quick reject succeeded");
return
}
debug!("quick reject failed: could possibly unify");
}
None => {
debug!("quick reject failed: impl type {} was \
unsimplifiable",
self.ty_to_string(impl_type.ty));
}
}
}
None => {
if is_extension {
debug!("quick reject failed: callee is unsimplifiable");
}
}
}

debug!("push_candidates_from_impl: {} {}",
token::get_name(self.m_name),
impl_items.iter()
Expand Down
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