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Optimize TyCtxt::hygienic_eq.

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It's measurably faster to avoid the context comparison when possible.

The commit also adds `hygienic_eq` in one appropriate place.
This commit is contained in:
Nicholas Nethercote 2019-05-28 06:19:23 +10:00
parent caea42f6c8
commit 2ca6facaaf
1 changed files with 7 additions and 2 deletions
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9
src/librustc/ty/mod.rs
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@ -2886,7 +2886,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> {
variant.fields.iter().position(|field| {
self.adjust_ident(ident, variant.def_id, hir::DUMMY_HIR_ID).0 == field.ident.modern()
self.hygienic_eq(ident, field.ident, variant.def_id)
})
}
@ -3085,7 +3085,12 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
/// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed
/// definition's parent/scope to perform comparison.
pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool {
self.adjust_ident(use_name, def_parent_def_id, hir::DUMMY_HIR_ID).0 == def_name.modern()
// We could use `Ident::eq` here, but we deliberately don't. The name
// comparison fails frequently, and we want to avoid the expensive
// `modern()` calls required for the span comparison whenever possible.
use_name.name == def_name.name &&
self.adjust_ident(use_name, def_parent_def_id, hir::DUMMY_HIR_ID).0.span.ctxt() ==
def_name.modern().span.ctxt()
}
pub fn adjust_ident(self, mut ident: Ident, scope: DefId, block: hir::HirId) -> (Ident, DefId) {