Unify validity checks into a single query

Previously, there were two queries to check whether a type allows the
0x01 or zeroed bitpattern.

I am planning on adding a further initness to check, truly uninit for
MaybeUninit, which would make this three queries. This seems overkill
for such a small feature, so this PR unifies them into one.

compiler/rustc_middle/src/query/keys.rs

@@ -4,8 +4,9 @@ use crate::infer::canonical::Canonical;
 use crate::mir;
 use crate::traits;
 use crate::ty::fast_reject::SimplifiedType;
+use crate::ty::layout::{InitKind, TyAndLayout};
 use crate::ty::subst::{GenericArg, SubstsRef};
-use crate::ty::{self, layout::TyAndLayout, Ty, TyCtxt};
+use crate::ty::{self, Ty, TyCtxt};
 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
 use rustc_hir::hir_id::{HirId, OwnerId};
 use rustc_query_system::query::{DefaultCacheSelector, SingleCacheSelector, VecCacheSelector};
@@ -696,3 +697,24 @@ impl Key for HirId {
         None
     }
 }
+
+impl<'tcx> Key for (InitKind, ty::ParamEnvAnd<'tcx, Ty<'tcx>>) {
+    type CacheSelector = DefaultCacheSelector<Self>;
+
+    // Just forward to `Ty<'tcx>`
+    #[inline(always)]
+    fn query_crate_is_local(&self) -> bool {
+        true
+    }
+
+    fn default_span(&self, _: TyCtxt<'_>) -> Span {
+        DUMMY_SP
+    }
+
+    fn ty_adt_id(&self) -> Option<DefId> {
+        match self.1.value.kind() {
+            ty::Adt(adt, _) => Some(adt.did()),
+            _ => None,
+        }
+    }
+}

compiler/rustc_middle/src/query/mod.rs

@@ -2173,12 +2173,8 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query permits_uninit_init(key: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> Result<bool, ty::layout::LayoutError<'tcx>> {
-        desc { "checking to see if `{}` permits being left uninit", key.value }
-    }
-
-    query permits_zero_init(key: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> Result<bool, ty::layout::LayoutError<'tcx>> {
-        desc { "checking to see if `{}` permits being left zeroed", key.value }
+    query check_validity_of_init(key: (InitKind, ty::ParamEnvAnd<'tcx, Ty<'tcx>>)) -> Result<bool, ty::layout::LayoutError<'tcx>> {
+        desc { "checking to see if `{}` permits being left {}", key.1.value, key.0 }
     }
 
     query compare_impl_const(

compiler/rustc_middle/src/ty/layout.rs

@@ -169,6 +169,23 @@ pub const FAT_PTR_EXTRA: usize = 1;
 /// * Cranelift stores the base-2 log of the lane count in a 4 bit integer.
 pub const MAX_SIMD_LANES: u64 = 1 << 0xF;
 
+/// Used in `might_permit_raw_init` to indicate the kind of initialisation
+/// that is checked to be valid
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
+pub enum InitKind {
+    Zero,
+    UninitMitigated0x01Fill,
+}
+
+impl fmt::Display for InitKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Zero => f.write_str("zeroed"),
+            Self::UninitMitigated0x01Fill => f.write_str("filled with 0x01"),
+        }
+    }
+}
+
 #[derive(Copy, Clone, Debug, HashStable, TyEncodable, TyDecodable)]
 pub enum LayoutError<'tcx> {
     Unknown(Ty<'tcx>),

compiler/rustc_middle/src/ty/query.rs

@@ -32,6 +32,7 @@ use crate::traits::specialization_graph;
 use crate::traits::{self, ImplSource};
 use crate::ty::context::TyCtxtFeed;
 use crate::ty::fast_reject::SimplifiedType;
+use crate::ty::layout::InitKind;
 use crate::ty::subst::{GenericArg, SubstsRef};
 use crate::ty::util::AlwaysRequiresDrop;
 use crate::ty::GeneratorDiagnosticData;