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Auto merge of #107627 - nnethercote:optimize-fold_ty, r=compiler-errors
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Optimize `fold_ty`

Micro-optimizing the heck out of the important `fold_ty` methods.

r? `@oli-obk`
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@bors
bors committed Feb 5, 2023
2 parents 75a0be9 + 4aec134 commit 14ea63a
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Showing 3 changed files with 104 additions and 99 deletions.
129 changes: 61 additions & 68 deletions compiler/rustc_infer/src/infer/freshen.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -140,79 +140,21 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
}
}

#[inline]
fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
if !t.needs_infer() && !t.has_erasable_regions() {
return t;
}

let tcx = self.infcx.tcx;

match *t.kind() {
ty::Infer(ty::TyVar(v)) => {
let opt_ty = self.infcx.inner.borrow_mut().type_variables().probe(v).known();
self.freshen_ty(opt_ty, ty::TyVar(v), ty::FreshTy)
}
t
} else {
match *t.kind() {
ty::Infer(v) => self.fold_infer_ty(v).unwrap_or(t),

ty::Infer(ty::IntVar(v)) => self.freshen_ty(
self.infcx
.inner
.borrow_mut()
.int_unification_table()
.probe_value(v)
.map(|v| v.to_type(tcx)),
ty::IntVar(v),
ty::FreshIntTy,
),
// This code is hot enough that a non-debug assertion here makes a noticeable
// difference on benchmarks like `wg-grammar`.
#[cfg(debug_assertions)]
ty::Placeholder(..) | ty::Bound(..) => bug!("unexpected type {:?}", t),

ty::Infer(ty::FloatVar(v)) => self.freshen_ty(
self.infcx
.inner
.borrow_mut()
.float_unification_table()
.probe_value(v)
.map(|v| v.to_type(tcx)),
ty::FloatVar(v),
ty::FreshFloatTy,
),

ty::Infer(ty::FreshTy(ct) | ty::FreshIntTy(ct) | ty::FreshFloatTy(ct)) => {
if ct >= self.ty_freshen_count {
bug!(
"Encountered a freshend type with id {} \
but our counter is only at {}",
ct,
self.ty_freshen_count
);
}
t
_ => t.super_fold_with(self),
}

ty::Generator(..)
| ty::Bool
| ty::Char
| ty::Int(..)
| ty::Uint(..)
| ty::Float(..)
| ty::Adt(..)
| ty::Str
| ty::Error(_)
| ty::Array(..)
| ty::Slice(..)
| ty::RawPtr(..)
| ty::Ref(..)
| ty::FnDef(..)
| ty::FnPtr(_)
| ty::Dynamic(..)
| ty::Never
| ty::Tuple(..)
| ty::Alias(..)
| ty::Foreign(..)
| ty::Param(..)
| ty::Closure(..)
| ty::GeneratorWitnessMIR(..)
| ty::GeneratorWitness(..) => t.super_fold_with(self),

ty::Placeholder(..) | ty::Bound(..) => bug!("unexpected type {:?}", t),
}
}

Expand Down Expand Up @@ -253,3 +195,54 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
}
}
}

impl<'a, 'tcx> TypeFreshener<'a, 'tcx> {
// This is separate from `fold_ty` to keep that method small and inlinable.
#[inline(never)]
fn fold_infer_ty(&mut self, v: ty::InferTy) -> Option<Ty<'tcx>> {
match v {
ty::TyVar(v) => {
let opt_ty = self.infcx.inner.borrow_mut().type_variables().probe(v).known();
Some(self.freshen_ty(opt_ty, ty::TyVar(v), ty::FreshTy))
}

ty::IntVar(v) => Some(
self.freshen_ty(
self.infcx
.inner
.borrow_mut()
.int_unification_table()
.probe_value(v)
.map(|v| v.to_type(self.infcx.tcx)),
ty::IntVar(v),
ty::FreshIntTy,
),
),

ty::FloatVar(v) => Some(
self.freshen_ty(
self.infcx
.inner
.borrow_mut()
.float_unification_table()
.probe_value(v)
.map(|v| v.to_type(self.infcx.tcx)),
ty::FloatVar(v),
ty::FreshFloatTy,
),
),

ty::FreshTy(ct) | ty::FreshIntTy(ct) | ty::FreshFloatTy(ct) => {
if ct >= self.ty_freshen_count {
bug!(
"Encountered a freshend type with id {} \
but our counter is only at {}",
ct,
self.ty_freshen_count
);
}
None
}
}
}
}
61 changes: 35 additions & 26 deletions compiler/rustc_infer/src/infer/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@ use rustc_middle::ty::relate::RelateResult;
use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef};
use rustc_middle::ty::visit::TypeVisitable;
pub use rustc_middle::ty::IntVarValue;
use rustc_middle::ty::{self, GenericParamDefKind, InferConst, Ty, TyCtxt};
use rustc_middle::ty::{self, GenericParamDefKind, InferConst, InferTy, Ty, TyCtxt};
use rustc_middle::ty::{ConstVid, FloatVid, IntVid, TyVid};
use rustc_span::symbol::Symbol;
use rustc_span::Span;
Expand Down Expand Up @@ -1389,8 +1389,8 @@ impl<'tcx> InferCtxt<'tcx> {
where
T: TypeFoldable<'tcx>,
{
if !value.needs_infer() {
return value; // Avoid duplicated subst-folding.
if !value.has_non_region_infer() {
return value;
}
let mut r = resolve::OpportunisticVarResolver::new(self);
value.fold_with(&mut r)
Expand Down Expand Up @@ -1870,9 +1870,33 @@ impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> {
/// If `ty` is a type variable of some kind, resolve it one level
/// (but do not resolve types found in the result). If `typ` is
/// not a type variable, just return it unmodified.
#[inline]
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
match *ty.kind() {
ty::Infer(ty::TyVar(v)) => {
if let ty::Infer(v) = ty.kind() { self.fold_infer_ty(*v).unwrap_or(ty) } else { ty }
}

fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
if let ty::ConstKind::Infer(InferConst::Var(vid)) = ct.kind() {
self.infcx
.inner
.borrow_mut()
.const_unification_table()
.probe_value(vid)
.val
.known()
.unwrap_or(ct)
} else {
ct
}
}
}

impl<'a, 'tcx> ShallowResolver<'a, 'tcx> {
// This is separate from `fold_ty` to keep that method small and inlinable.
#[inline(never)]
fn fold_infer_ty(&mut self, v: InferTy) -> Option<Ty<'tcx>> {
match v {
ty::TyVar(v) => {
// Not entirely obvious: if `typ` is a type variable,
// it can be resolved to an int/float variable, which
// can then be recursively resolved, hence the
Expand All @@ -1886,41 +1910,26 @@ impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> {
// Note: if these two lines are combined into one we get
// dynamic borrow errors on `self.inner`.
let known = self.infcx.inner.borrow_mut().type_variables().probe(v).known();
known.map_or(ty, |t| self.fold_ty(t))
known.map(|t| self.fold_ty(t))
}

ty::Infer(ty::IntVar(v)) => self
ty::IntVar(v) => self
.infcx
.inner
.borrow_mut()
.int_unification_table()
.probe_value(v)
.map_or(ty, |v| v.to_type(self.infcx.tcx)),
.map(|v| v.to_type(self.infcx.tcx)),

ty::Infer(ty::FloatVar(v)) => self
ty::FloatVar(v) => self
.infcx
.inner
.borrow_mut()
.float_unification_table()
.probe_value(v)
.map_or(ty, |v| v.to_type(self.infcx.tcx)),
.map(|v| v.to_type(self.infcx.tcx)),

_ => ty,
}
}

fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
if let ty::ConstKind::Infer(InferConst::Var(vid)) = ct.kind() {
self.infcx
.inner
.borrow_mut()
.const_unification_table()
.probe_value(vid)
.val
.known()
.unwrap_or(ct)
} else {
ct
ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => None,
}
}
}
Expand Down
13 changes: 8 additions & 5 deletions compiler/rustc_infer/src/infer/resolve.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -16,26 +16,29 @@ use std::ops::ControlFlow;
/// useful for printing messages etc but also required at various
/// points for correctness.
pub struct OpportunisticVarResolver<'a, 'tcx> {
infcx: &'a InferCtxt<'tcx>,
// The shallow resolver is used to resolve inference variables at every
// level of the type.
shallow_resolver: crate::infer::ShallowResolver<'a, 'tcx>,
}

impl<'a, 'tcx> OpportunisticVarResolver<'a, 'tcx> {
#[inline]
pub fn new(infcx: &'a InferCtxt<'tcx>) -> Self {
OpportunisticVarResolver { infcx }
OpportunisticVarResolver { shallow_resolver: crate::infer::ShallowResolver { infcx } }
}
}

impl<'a, 'tcx> TypeFolder<'tcx> for OpportunisticVarResolver<'a, 'tcx> {
fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
self.infcx.tcx
TypeFolder::tcx(&self.shallow_resolver)
}

#[inline]
fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
if !t.has_non_region_infer() {
t // micro-optimize -- if there is nothing in this type that this fold affects...
} else {
let t = self.infcx.shallow_resolve(t);
let t = self.shallow_resolver.fold_ty(t);
t.super_fold_with(self)
}
}
Expand All @@ -44,7 +47,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for OpportunisticVarResolver<'a, 'tcx> {
if !ct.has_non_region_infer() {
ct // micro-optimize -- if there is nothing in this const that this fold affects...
} else {
let ct = self.infcx.shallow_resolve(ct);
let ct = self.shallow_resolver.fold_const(ct);
ct.super_fold_with(self)
}
}
Expand Down

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