diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs index 5ed5644bca19c..e7dd36d183aa9 100644 --- a/compiler/rustc_middle/src/ty/context.rs +++ b/compiler/rustc_middle/src/ty/context.rs @@ -243,11 +243,20 @@ impl<'tcx> CtxtInterners<'tcx> { } } +// For these preinterned values, an alternative would be to have +// variable-length vectors that grow as needed. But that turned out to be +// slightly more complex and no faster. + const NUM_PREINTERNED_TY_VARS: u32 = 100; const NUM_PREINTERNED_FRESH_TYS: u32 = 20; const NUM_PREINTERNED_FRESH_INT_TYS: u32 = 3; const NUM_PREINTERNED_FRESH_FLOAT_TYS: u32 = 3; +// 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; +const NUM_PREINTERNED_RE_LATE_BOUNDS_V: u32 = 20; + pub struct CommonTypes<'tcx> { pub unit: Ty<'tcx>, pub bool: Ty<'tcx>, @@ -295,6 +304,14 @@ pub struct CommonLifetimes<'tcx> { /// Erased region, used outside of type inference. pub re_erased: Region<'tcx>, + + /// Pre-interned `ReVar(ty::RegionVar(n))` for small values of `n`. + pub re_vars: Vec>, + + /// Pre-interned values of the form: + /// `ReLateBound(DebruijnIndex(i), BoundRegion { var: v, kind: BrAnon(v, None) }) + /// for small values of `i` and `v`. + pub re_late_bounds: Vec>>, } pub struct CommonConsts<'tcx> { @@ -358,7 +375,31 @@ impl<'tcx> CommonLifetimes<'tcx> { )) }; - CommonLifetimes { re_static: mk(ty::ReStatic), re_erased: mk(ty::ReErased) } + let re_vars = + (0..NUM_PREINTERNED_RE_VARS).map(|n| mk(ty::ReVar(ty::RegionVid::from(n)))).collect(); + + let re_late_bounds = (0..NUM_PREINTERNED_RE_LATE_BOUNDS_I) + .map(|i| { + (0..NUM_PREINTERNED_RE_LATE_BOUNDS_V) + .map(|v| { + mk(ty::ReLateBound( + ty::DebruijnIndex::from(i), + ty::BoundRegion { + var: ty::BoundVar::from(v), + kind: ty::BrAnon(v, None), + }, + )) + }) + .collect() + }) + .collect(); + + CommonLifetimes { + re_static: mk(ty::ReStatic), + re_erased: mk(ty::ReErased), + re_vars, + re_late_bounds, + } } } @@ -2002,7 +2043,16 @@ impl<'tcx> TyCtxt<'tcx> { debruijn: ty::DebruijnIndex, bound_region: ty::BoundRegion, ) -> Region<'tcx> { - self.intern_region(ty::ReLateBound(debruijn, bound_region)) + // Use a pre-interned one when possible. + if let ty::BoundRegion { var, kind: ty::BrAnon(v, None) } = bound_region + && var.as_u32() == v + && let Some(inner) = self.lifetimes.re_late_bounds.get(debruijn.as_usize()) + && let Some(re) = inner.get(v as usize).copied() + { + re + } else { + self.intern_region(ty::ReLateBound(debruijn, bound_region)) + } } #[inline] @@ -2011,8 +2061,13 @@ impl<'tcx> TyCtxt<'tcx> { } #[inline] - pub fn mk_re_var(self, vid: ty::RegionVid) -> Region<'tcx> { - self.intern_region(ty::ReVar(vid)) + pub fn mk_re_var(self, v: ty::RegionVid) -> Region<'tcx> { + // Use a pre-interned one when possible. + self.lifetimes + .re_vars + .get(v.as_usize()) + .copied() + .unwrap_or_else(|| self.intern_region(ty::ReVar(v))) } #[inline]