Merging upstream version 1.70.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

2 files changed, 12 insertions, 0 deletions

diff --git a/compiler/rustc_codegen_ssa/src/traits/consts.rs b/compiler/rustc_codegen_ssa/src/traits/consts.rs
index fdc7a30e8..619063027 100644
--- a/compiler/rustc_codegen_ssa/src/traits/consts.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/consts.rs
@@ -8,6 +8,7 @@ pub trait ConstMethods<'tcx>: BackendTypes {
     // Constant constructors
     fn const_null(&self, t: Self::Type) -> Self::Value;
     fn const_undef(&self, t: Self::Type) -> Self::Value;
+    fn const_poison(&self, t: Self::Type) -> Self::Value;
     fn const_int(&self, t: Self::Type, i: i64) -> Self::Value;
     fn const_uint(&self, t: Self::Type, i: u64) -> Self::Value;
     fn const_uint_big(&self, t: Self::Type, u: u128) -> Self::Value;
diff --git a/compiler/rustc_codegen_ssa/src/traits/type_.rs b/compiler/rustc_codegen_ssa/src/traits/type_.rs
index 109161ccc..32905b079 100644
--- a/compiler/rustc_codegen_ssa/src/traits/type_.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/type_.rs
@@ -100,11 +100,22 @@ pub trait DerivedTypeMethods<'tcx>: BaseTypeMethods<'tcx> + MiscMethods<'tcx> {
 impl<'tcx, T> DerivedTypeMethods<'tcx> for T where Self: BaseTypeMethods<'tcx> + MiscMethods<'tcx> {}
 
 pub trait LayoutTypeMethods<'tcx>: Backend<'tcx> {
+    /// The backend type used for a rust type when it's in memory,
+    /// such as when it's stack-allocated or when it's being loaded or stored.
     fn backend_type(&self, layout: TyAndLayout<'tcx>) -> Self::Type;
     fn cast_backend_type(&self, ty: &CastTarget) -> Self::Type;
     fn fn_decl_backend_type(&self, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> Self::Type;
     fn fn_ptr_backend_type(&self, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> Self::Type;
     fn reg_backend_type(&self, ty: &Reg) -> Self::Type;
+    /// The backend type used for a rust type when it's in an SSA register.
+    ///
+    /// For nearly all types this is the same as the [`Self::backend_type`], however
+    /// `bool` (and other `0`-or-`1` values) are kept as [`BaseTypeMethods::type_i1`]
+    /// in registers but as [`BaseTypeMethods::type_i8`] in memory.
+    ///
+    /// Converting values between the two different backend types is done using
+    /// [`from_immediate`](super::BuilderMethods::from_immediate) and
+    /// [`to_immediate_scalar`](super::BuilderMethods::to_immediate_scalar).
     fn immediate_backend_type(&self, layout: TyAndLayout<'tcx>) -> Self::Type;
     fn is_backend_immediate(&self, layout: TyAndLayout<'tcx>) -> bool;
     fn is_backend_scalar_pair(&self, layout: TyAndLayout<'tcx>) -> bool;