Auto merge of #117166 - oli-obk:mir_const_qualif_perf, r=petrochenkov

Only call `mir_const_qualif` if absolutely necessary

Pull the perf change out of https://github.com/rust-lang/rust/pull/113617

This should not have any impact on behaviour (if it does, we'll see an ICE)
This commit is contained in:
bors 2023-10-27 16:06:02 +00:00
commit 10143e781b

View File

@ -20,6 +20,7 @@
#[macro_use] #[macro_use]
extern crate rustc_middle; extern crate rustc_middle;
use hir::ConstContext;
use required_consts::RequiredConstsVisitor; use required_consts::RequiredConstsVisitor;
use rustc_const_eval::util; use rustc_const_eval::util;
use rustc_data_structures::fx::FxIndexSet; use rustc_data_structures::fx::FxIndexSet;
@ -251,8 +252,13 @@ fn mir_const_qualif(tcx: TyCtxt<'_>, def: LocalDefId) -> ConstQualifs {
let const_kind = tcx.hir().body_const_context(def); let const_kind = tcx.hir().body_const_context(def);
// No need to const-check a non-const `fn`. // No need to const-check a non-const `fn`.
if const_kind.is_none() { match const_kind {
return Default::default(); Some(ConstContext::Const { .. } | ConstContext::Static(_))
| Some(ConstContext::ConstFn) => {}
None => span_bug!(
tcx.def_span(def),
"`mir_const_qualif` should only be called on const fns and const items"
),
} }
// N.B., this `borrow()` is guaranteed to be valid (i.e., the value // N.B., this `borrow()` is guaranteed to be valid (i.e., the value
@ -317,7 +323,21 @@ fn mir_promoted(
// Ensure that we compute the `mir_const_qualif` for constants at // Ensure that we compute the `mir_const_qualif` for constants at
// this point, before we steal the mir-const result. // this point, before we steal the mir-const result.
// Also this means promotion can rely on all const checks having been done. // Also this means promotion can rely on all const checks having been done.
let const_qualifs = tcx.mir_const_qualif(def);
let const_qualifs = match tcx.def_kind(def) {
DefKind::Fn | DefKind::AssocFn | DefKind::Closure
if tcx.constness(def) == hir::Constness::Const
|| tcx.is_const_default_method(def.to_def_id()) =>
{
tcx.mir_const_qualif(def)
}
DefKind::AssocConst
| DefKind::Const
| DefKind::Static(_)
| DefKind::InlineConst
| DefKind::AnonConst => tcx.mir_const_qualif(def),
_ => ConstQualifs::default(),
};
let mut body = tcx.mir_const(def).steal(); let mut body = tcx.mir_const(def).steal();
if let Some(error_reported) = const_qualifs.tainted_by_errors { if let Some(error_reported) = const_qualifs.tainted_by_errors {
body.tainted_by_errors = Some(error_reported); body.tainted_by_errors = Some(error_reported);