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Pre-intern some const infer vars #141499

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Pre-intern some const infer vars #141499

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f1ff041
Use Ty::new_var quick path
compiler-errors May 24, 2025
5771471
Fast path pre-intern const infer vars
compiler-errors May 24, 2025
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2 changes: 1 addition & 1 deletion compiler/rustc_borrowck/src/type_check/relate_tys.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -139,7 +139,7 @@ impl<'a, 'b, 'tcx> NllTypeRelating<'a, 'b, 'tcx> {
variance,
ty,
)?;
Ok(infcx.resolve_vars_if_possible(Ty::new_infer(infcx.tcx, ty::TyVar(ty_vid))))
Ok(infcx.resolve_vars_if_possible(Ty::new_var(infcx.tcx, ty_vid)))
};

let (a, b) = match (a.kind(), b.kind()) {
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9 changes: 7 additions & 2 deletions compiler/rustc_middle/src/ty/consts.rs
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Expand Up @@ -75,8 +75,13 @@ impl<'tcx> Const<'tcx> {
}

#[inline]
pub fn new_var(tcx: TyCtxt<'tcx>, infer: ty::ConstVid) -> Const<'tcx> {
Const::new(tcx, ty::ConstKind::Infer(ty::InferConst::Var(infer)))
pub fn new_var(tcx: TyCtxt<'tcx>, v: ty::ConstVid) -> Const<'tcx> {
// Use a pre-interned one when possible.
tcx.consts
.ct_vars
.get(v.as_usize())
.copied()
.unwrap_or_else(|| Const::new(tcx, ty::ConstKind::Infer(ty::InferConst::Var(v))))
}

#[inline]
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9 changes: 9 additions & 0 deletions compiler/rustc_middle/src/ty/context.rs
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Expand Up @@ -1014,6 +1014,8 @@ const NUM_PREINTERNED_FRESH_TYS: u32 = 20;
const NUM_PREINTERNED_FRESH_INT_TYS: u32 = 3;
const NUM_PREINTERNED_FRESH_FLOAT_TYS: u32 = 3;

const NUM_PREINTERNED_CT_VARS: u32 = 100;

// This number may seem high, but it is reached in all but the smallest crates.
const NUM_PREINTERNED_RE_VARS: u32 = 500;
const NUM_PREINTERNED_RE_LATE_BOUNDS_I: u32 = 2;
Expand Down Expand Up @@ -1084,6 +1086,8 @@ pub struct CommonConsts<'tcx> {
pub false_: Const<'tcx>,
/// Use [`ty::ValTree::zst`] instead.
pub(crate) valtree_zst: ValTree<'tcx>,
/// Pre-interned `ConstKind::Infer(InferConst::Var(n))` for small values of `n`.
pub ct_vars: Vec<Const<'tcx>>,
}

impl<'tcx> CommonTypes<'tcx> {
Expand Down Expand Up @@ -1197,6 +1201,10 @@ impl<'tcx> CommonConsts<'tcx> {
let valtree_true = mk_valtree(ty::ValTreeKind::Leaf(ty::ScalarInt::TRUE));
let valtree_false = mk_valtree(ty::ValTreeKind::Leaf(ty::ScalarInt::FALSE));

let ct_vars = (0..NUM_PREINTERNED_CT_VARS)
.map(|n| mk_const(ty::ConstKind::Infer(ty::InferConst::Var(ty::ConstVid::from(n)))))
.collect();

CommonConsts {
unit: mk_const(ty::ConstKind::Value(ty::Value {
ty: types.unit,
Expand All @@ -1210,6 +1218,7 @@ impl<'tcx> CommonConsts<'tcx> {
ty: types.bool,
valtree: valtree_false,
})),
ct_vars,
valtree_zst,
}
}
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