Remove `BackendRepr::Uninhabited`, replaced with an `uninhabited: bool` field in `LayoutData`.

Also update comments that refered to BackendRepr::Uninhabited.

6 files changed, 5 insertions, 10 deletions

diff --git a/compiler/rustc_target/src/callconv/loongarch.rs b/compiler/rustc_target/src/callconv/loongarch.rs
index 47566bde6b4..3fa67c624a7 100644
--- a/compiler/rustc_target/src/callconv/loongarch.rs
+++ b/compiler/rustc_target/src/callconv/loongarch.rs
@@ -80,7 +80,7 @@ where
                 }
             }
         },
-        BackendRepr::Vector { .. } | BackendRepr::Uninhabited => return Err(CannotUseFpConv),
+        BackendRepr::Vector { .. } => return Err(CannotUseFpConv),
         BackendRepr::ScalarPair(..) | BackendRepr::Memory { .. } => match arg_layout.fields {
             FieldsShape::Primitive => {
                 unreachable!("aggregates can't have `FieldsShape::Primitive`")
diff --git a/compiler/rustc_target/src/callconv/mod.rs b/compiler/rustc_target/src/callconv/mod.rs
index c2a176facdf..e5f986269dd 100644
--- a/compiler/rustc_target/src/callconv/mod.rs
+++ b/compiler/rustc_target/src/callconv/mod.rs
@@ -38,7 +38,7 @@ mod xtensa;
 pub enum PassMode {
     /// Ignore the argument.
     ///
-    /// The argument is either uninhabited or a ZST.
+    /// The argument is a ZST.
     Ignore,
     /// Pass the argument directly.
     ///
@@ -350,7 +350,6 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
         scalar_attrs: impl Fn(&TyAndLayout<'a, Ty>, Scalar, Size) -> ArgAttributes,
     ) -> Self {
         let mode = match layout.backend_repr {
-            BackendRepr::Uninhabited => PassMode::Ignore,
             BackendRepr::Scalar(scalar) => {
                 PassMode::Direct(scalar_attrs(&layout, scalar, Size::ZERO))
             }
diff --git a/compiler/rustc_target/src/callconv/riscv.rs b/compiler/rustc_target/src/callconv/riscv.rs
index 265ae20f991..785175229b0 100644
--- a/compiler/rustc_target/src/callconv/riscv.rs
+++ b/compiler/rustc_target/src/callconv/riscv.rs
@@ -86,7 +86,7 @@ where
                 }
             }
         },
-        BackendRepr::Vector { .. } | BackendRepr::Uninhabited => return Err(CannotUseFpConv),
+        BackendRepr::Vector { .. } => return Err(CannotUseFpConv),
         BackendRepr::ScalarPair(..) | BackendRepr::Memory { .. } => match arg_layout.fields {
             FieldsShape::Primitive => {
                 unreachable!("aggregates can't have `FieldsShape::Primitive`")
diff --git a/compiler/rustc_target/src/callconv/x86.rs b/compiler/rustc_target/src/callconv/x86.rs
index 5f4f4cd57f6..7e5aab0201b 100644
--- a/compiler/rustc_target/src/callconv/x86.rs
+++ b/compiler/rustc_target/src/callconv/x86.rs
@@ -108,9 +108,7 @@ where
                 Ty: TyAbiInterface<'a, C> + Copy,
             {
                 match layout.backend_repr {
-                    BackendRepr::Uninhabited
-                    | BackendRepr::Scalar(_)
-                    | BackendRepr::ScalarPair(..) => false,
+                    BackendRepr::Scalar(_) | BackendRepr::ScalarPair(..) => false,
                     BackendRepr::Vector { .. } => true,
                     BackendRepr::Memory { .. } => {
                         for i in 0..layout.fields.count() {
diff --git a/compiler/rustc_target/src/callconv/x86_64.rs b/compiler/rustc_target/src/callconv/x86_64.rs
index b15d82c26da..ab306e20239 100644
--- a/compiler/rustc_target/src/callconv/x86_64.rs
+++ b/compiler/rustc_target/src/callconv/x86_64.rs
@@ -51,8 +51,6 @@ where
         }
 
         let mut c = match layout.backend_repr {
-            BackendRepr::Uninhabited => return Ok(()),
-
             BackendRepr::Scalar(scalar) => match scalar.primitive() {
                 Primitive::Int(..) | Primitive::Pointer(_) => Class::Int,
                 Primitive::Float(_) => Class::Sse,
diff --git a/compiler/rustc_target/src/callconv/x86_win64.rs b/compiler/rustc_target/src/callconv/x86_win64.rs
index 2ef5127de04..4d99a9f9ba0 100644
--- a/compiler/rustc_target/src/callconv/x86_win64.rs
+++ b/compiler/rustc_target/src/callconv/x86_win64.rs
@@ -8,7 +8,7 @@ use crate::spec::{HasTargetSpec, RustcAbi};
 pub(crate) fn compute_abi_info<Ty>(cx: &impl HasTargetSpec, fn_abi: &mut FnAbi<'_, Ty>) {
     let fixup = |a: &mut ArgAbi<'_, Ty>, is_ret: bool| {
         match a.layout.backend_repr {
-            BackendRepr::Uninhabited | BackendRepr::Memory { sized: false } => {}
+            BackendRepr::Memory { sized: false } => {}
             BackendRepr::ScalarPair(..) | BackendRepr::Memory { sized: true } => {
                 match a.layout.size.bits() {
                     8 => a.cast_to(Reg::i8()),