From eb74096a32702e45bb9cd8d1c2c787c2067272d8 Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Thu, 9 Apr 2020 14:56:19 -0700 Subject: [PATCH] Avoid calling `fn_sig` query during `is_const_fn_raw` --- src/librustc_mir/const_eval/fn_queries.rs | 27 +++++++++-------------- 1 file changed, 10 insertions(+), 17 deletions(-) diff --git a/src/librustc_mir/const_eval/fn_queries.rs b/src/librustc_mir/const_eval/fn_queries.rs index 8ae4f9f4a0d6e..bf438ead84079 100644 --- a/src/librustc_mir/const_eval/fn_queries.rs +++ b/src/librustc_mir/const_eval/fn_queries.rs @@ -99,8 +99,16 @@ fn is_const_fn_raw(tcx: TyCtxt<'_>, def_id: DefId) -> bool { let node = tcx.hir().get(hir_id); - if let Some(whitelisted) = is_const_intrinsic(tcx, def_id) { - whitelisted + if let hir::Node::ForeignItem(hir::ForeignItem { kind: hir::ForeignItemKind::Fn(..), .. }) = + node + { + // Intrinsics use `rustc_const_{un,}stable` attributes to indicate constness. All other + // foreign items cannot be evaluated at compile-time. + if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = tcx.hir().get_foreign_abi(hir_id) { + tcx.lookup_const_stability(def_id).is_some() + } else { + false + } } else if let Some(fn_like) = FnLikeNode::from_node(node) { if fn_like.constness() == hir::Constness::Const { return true; @@ -116,21 +124,6 @@ fn is_const_fn_raw(tcx: TyCtxt<'_>, def_id: DefId) -> bool { } } -/// Const evaluability whitelist is here to check evaluability at the -/// top level beforehand. -fn is_const_intrinsic(tcx: TyCtxt<'_>, def_id: DefId) -> Option { - if tcx.is_closure(def_id) { - return None; - } - - match tcx.fn_sig(def_id).abi() { - Abi::RustIntrinsic | Abi::PlatformIntrinsic => { - Some(tcx.lookup_const_stability(def_id).is_some()) - } - _ => None, - } -} - /// Checks whether the given item is an `impl` that has a `const` modifier. fn is_const_impl_raw(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool { let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);