Box `CastTarget` within `PassMode`.

Because `PassMode::Cast` is by far the largest variant, but is
relatively rare.

This requires making `PassMode` not impl `Copy`, and `Clone` is no
longer necessary. This causes lots of sigil adjusting, but nothing very
notable.

11 files changed, 57 insertions, 57 deletions

diff --git a/compiler/rustc_codegen_cranelift/src/abi/comments.rs b/compiler/rustc_codegen_cranelift/src/abi/comments.rs
index 37d2679c10d..7f4619b5c94 100644
--- a/compiler/rustc_codegen_cranelift/src/abi/comments.rs
+++ b/compiler/rustc_codegen_cranelift/src/abi/comments.rs
@@ -24,7 +24,7 @@ pub(super) fn add_arg_comment<'tcx>(
     local: Option<mir::Local>,
     local_field: Option<usize>,
     params: &[Value],
-    arg_abi_mode: PassMode,
+    arg_abi_mode: &PassMode,
     arg_layout: TyAndLayout<'tcx>,
 ) {
     if !fx.clif_comments.enabled() {
diff --git a/compiler/rustc_codegen_cranelift/src/abi/pass_mode.rs b/compiler/rustc_codegen_cranelift/src/abi/pass_mode.rs
index 6c10baa53d4..058dee176e2 100644
--- a/compiler/rustc_codegen_cranelift/src/abi/pass_mode.rs
+++ b/compiler/rustc_codegen_cranelift/src/abi/pass_mode.rs
@@ -38,7 +38,7 @@ fn apply_arg_attrs_to_abi_param(mut param: AbiParam, arg_attrs: ArgAttributes) -
     param
 }
 
-fn cast_target_to_abi_params(cast: CastTarget) -> SmallVec<[AbiParam; 2]> {
+fn cast_target_to_abi_params(cast: &CastTarget) -> SmallVec<[AbiParam; 2]> {
     let (rest_count, rem_bytes) = if cast.rest.unit.size.bytes() == 0 {
         (0, 0)
     } else {
@@ -100,7 +100,7 @@ impl<'tcx> ArgAbiExt<'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
                 }
                 _ => unreachable!("{:?}", self.layout.abi),
             },
-            PassMode::Cast(cast) => cast_target_to_abi_params(cast),
+            PassMode::Cast(ref cast) => cast_target_to_abi_params(cast),
             PassMode::Indirect { attrs, extra_attrs: None, on_stack } => {
                 if on_stack {
                     // Abi requires aligning struct size to pointer size
@@ -145,7 +145,9 @@ impl<'tcx> ArgAbiExt<'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
                 }
                 _ => unreachable!("{:?}", self.layout.abi),
             },
-            PassMode::Cast(cast) => (None, cast_target_to_abi_params(cast).into_iter().collect()),
+            PassMode::Cast(ref cast) => {
+                (None, cast_target_to_abi_params(cast).into_iter().collect())
+            }
             PassMode::Indirect { attrs: _, extra_attrs: None, on_stack } => {
                 assert!(!on_stack);
                 (Some(AbiParam::special(pointer_ty(tcx), ArgumentPurpose::StructReturn)), vec![])
@@ -160,7 +162,7 @@ impl<'tcx> ArgAbiExt<'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
 pub(super) fn to_casted_value<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     arg: CValue<'tcx>,
-    cast: CastTarget,
+    cast: &CastTarget,
 ) -> SmallVec<[Value; 2]> {
     let (ptr, meta) = arg.force_stack(fx);
     assert!(meta.is_none());
@@ -179,7 +181,7 @@ pub(super) fn from_casted_value<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     block_params: &[Value],
     layout: TyAndLayout<'tcx>,
-    cast: CastTarget,
+    cast: &CastTarget,
 ) -> CValue<'tcx> {
     let abi_params = cast_target_to_abi_params(cast);
     let abi_param_size: u32 = abi_params.iter().map(|param| param.value_type.bytes()).sum();
@@ -224,7 +226,7 @@ pub(super) fn adjust_arg_for_abi<'tcx>(
             let (a, b) = arg.load_scalar_pair(fx);
             smallvec![a, b]
         }
-        PassMode::Cast(cast) => to_casted_value(fx, arg, cast),
+        PassMode::Cast(ref cast) => to_casted_value(fx, arg, cast),
         PassMode::Indirect { .. } => {
             if is_owned {
                 match arg.force_stack(fx) {
@@ -268,7 +270,7 @@ pub(super) fn cvalue_for_param<'tcx>(
         local,
         local_field,
         &block_params,
-        arg_abi.mode,
+        &arg_abi.mode,
         arg_abi.layout,
     );
 
@@ -282,7 +284,9 @@ pub(super) fn cvalue_for_param<'tcx>(
             assert_eq!(block_params.len(), 2, "{:?}", block_params);
             Some(CValue::by_val_pair(block_params[0], block_params[1], arg_abi.layout))
         }
-        PassMode::Cast(cast) => Some(from_casted_value(fx, &block_params, arg_abi.layout, cast)),
+        PassMode::Cast(ref cast) => {
+            Some(from_casted_value(fx, &block_params, arg_abi.layout, cast))
+        }
         PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ } => {
             assert_eq!(block_params.len(), 1, "{:?}", block_params);
             Some(CValue::by_ref(Pointer::new(block_params[0]), arg_abi.layout))
diff --git a/compiler/rustc_codegen_cranelift/src/abi/returning.rs b/compiler/rustc_codegen_cranelift/src/abi/returning.rs
index ff3bb2dfd00..29ef5e2dfda 100644
--- a/compiler/rustc_codegen_cranelift/src/abi/returning.rs
+++ b/compiler/rustc_codegen_cranelift/src/abi/returning.rs
@@ -44,7 +44,7 @@ pub(super) fn codegen_return_param<'tcx>(
         Some(RETURN_PLACE),
         None,
         &ret_param,
-        fx.fn_abi.as_ref().unwrap().ret.mode,
+        &fx.fn_abi.as_ref().unwrap().ret.mode,
         fx.fn_abi.as_ref().unwrap().ret.layout,
     );
 
@@ -92,7 +92,7 @@ pub(super) fn codegen_with_call_return_arg<'tcx>(
             ret_place
                 .write_cvalue(fx, CValue::by_val_pair(ret_val_a, ret_val_b, ret_arg_abi.layout));
         }
-        PassMode::Cast(cast) => {
+        PassMode::Cast(ref cast) => {
             let results =
                 fx.bcx.inst_results(call_inst).iter().copied().collect::<SmallVec<[Value; 2]>>();
             let result =
@@ -131,7 +131,7 @@ pub(crate) fn codegen_return(fx: &mut FunctionCx<'_, '_, '_>) {
             let (ret_val_a, ret_val_b) = place.to_cvalue(fx).load_scalar_pair(fx);
             fx.bcx.ins().return_(&[ret_val_a, ret_val_b]);
         }
-        PassMode::Cast(cast) => {
+        PassMode::Cast(ref cast) => {
             let place = fx.get_local_place(RETURN_PLACE);
             let ret_val = place.to_cvalue(fx);
             let ret_vals = super::pass_mode::to_casted_value(fx, ret_val, cast);
diff --git a/compiler/rustc_codegen_gcc/src/abi.rs b/compiler/rustc_codegen_gcc/src/abi.rs
index 0ed3e1fbe93..9b55db6a547 100644
--- a/compiler/rustc_codegen_gcc/src/abi.rs
+++ b/compiler/rustc_codegen_gcc/src/abi.rs
@@ -133,7 +133,7 @@ impl<'gcc, 'tcx> FnAbiGccExt<'gcc, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             match self.ret.mode {
                 PassMode::Ignore => cx.type_void(),
                 PassMode::Direct(_) | PassMode::Pair(..) => self.ret.layout.immediate_gcc_type(cx),
-                PassMode::Cast(cast) => cast.gcc_type(cx),
+                PassMode::Cast(ref cast) => cast.gcc_type(cx),
                 PassMode::Indirect { .. } => {
                     argument_tys.push(cx.type_ptr_to(self.ret.memory_ty(cx)));
                     cx.type_void()
@@ -157,7 +157,7 @@ impl<'gcc, 'tcx> FnAbiGccExt<'gcc, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
                 PassMode::Indirect { extra_attrs: Some(_), .. } => {
                     unimplemented!();
                 }
-                PassMode::Cast(cast) => cast.gcc_type(cx),
+                PassMode::Cast(ref cast) => cast.gcc_type(cx),
                 PassMode::Indirect { extra_attrs: None, on_stack: true, .. } => {
                     on_stack_param_indices.insert(argument_tys.len());
                     arg.memory_ty(cx)
diff --git a/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs b/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
index 5fbdedac0c4..f4493776ea2 100644
--- a/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
+++ b/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
@@ -130,7 +130,7 @@ impl<'a, 'gcc, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
                 sym::volatile_load | sym::unaligned_volatile_load => {
                     let tp_ty = substs.type_at(0);
                     let mut ptr = args[0].immediate();
-                    if let PassMode::Cast(ty) = fn_abi.ret.mode {
+                    if let PassMode::Cast(ty) = &fn_abi.ret.mode {
                         ptr = self.pointercast(ptr, self.type_ptr_to(ty.gcc_type(self)));
                     }
                     let load = self.volatile_load(ptr.get_type(), ptr);
@@ -320,7 +320,7 @@ impl<'a, 'gcc, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
             };
 
         if !fn_abi.ret.is_ignore() {
-            if let PassMode::Cast(ty) = fn_abi.ret.mode {
+            if let PassMode::Cast(ty) = &fn_abi.ret.mode {
                 let ptr_llty = self.type_ptr_to(ty.gcc_type(self));
                 let ptr = self.pointercast(result.llval, ptr_llty);
                 self.store(llval, ptr, result.align);
@@ -416,7 +416,7 @@ impl<'gcc, 'tcx> ArgAbiExt<'gcc, 'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
         else if self.is_unsized_indirect() {
             bug!("unsized `ArgAbi` must be handled through `store_fn_arg`");
         }
-        else if let PassMode::Cast(cast) = self.mode {
+        else if let PassMode::Cast(ref cast) = self.mode {
             // FIXME(eddyb): Figure out when the simpler Store is safe, clang
             // uses it for i16 -> {i8, i8}, but not for i24 -> {i8, i8, i8}.
             let can_store_through_cast_ptr = false;
diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
index 9eb3574e77b..09c53afa6c8 100644
--- a/compiler/rustc_codegen_llvm/src/abi.rs
+++ b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -213,7 +213,7 @@ impl<'ll, 'tcx> ArgAbiExt<'ll, 'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
             OperandValue::Ref(val, None, self.layout.align.abi).store(bx, dst)
         } else if self.is_unsized_indirect() {
             bug!("unsized `ArgAbi` must be handled through `store_fn_arg`");
-        } else if let PassMode::Cast(cast) = self.mode {
+        } else if let PassMode::Cast(cast) = &self.mode {
             // FIXME(eddyb): Figure out when the simpler Store is safe, clang
             // uses it for i16 -> {i8, i8}, but not for i24 -> {i8, i8, i8}.
             let can_store_through_cast_ptr = false;
@@ -335,7 +335,7 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             if let PassMode::Indirect { .. } = self.ret.mode { 1 } else { 0 } + args_capacity,
         );
 
-        let llreturn_ty = match self.ret.mode {
+        let llreturn_ty = match &self.ret.mode {
             PassMode::Ignore => cx.type_void(),
             PassMode::Direct(_) | PassMode::Pair(..) => self.ret.layout.immediate_llvm_type(cx),
             PassMode::Cast(cast) => cast.llvm_type(cx),
@@ -351,7 +351,7 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
                 llargument_tys.push(ty.llvm_type(cx));
             }
 
-            let llarg_ty = match arg.mode {
+            let llarg_ty = match &arg.mode {
                 PassMode::Ignore => continue,
                 PassMode::Direct(_) => arg.layout.immediate_llvm_type(cx),
                 PassMode::Pair(..) => {
@@ -426,11 +426,11 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             i += 1;
             i - 1
         };
-        match self.ret.mode {
-            PassMode::Direct(ref attrs) => {
+        match &self.ret.mode {
+            PassMode::Direct(attrs) => {
                 attrs.apply_attrs_to_llfn(llvm::AttributePlace::ReturnValue, cx, llfn);
             }
-            PassMode::Indirect { ref attrs, extra_attrs: _, on_stack } => {
+            PassMode::Indirect { attrs, extra_attrs: _, on_stack } => {
                 assert!(!on_stack);
                 let i = apply(attrs);
                 let sret = llvm::CreateStructRetAttr(cx.llcx, self.ret.layout.llvm_type(cx));
@@ -445,23 +445,23 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             if arg.pad.is_some() {
                 apply(&ArgAttributes::new());
             }
-            match arg.mode {
+            match &arg.mode {
                 PassMode::Ignore => {}
-                PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: true } => {
+                PassMode::Indirect { attrs, extra_attrs: None, on_stack: true } => {
                     let i = apply(attrs);
                     let byval = llvm::CreateByValAttr(cx.llcx, arg.layout.llvm_type(cx));
                     attributes::apply_to_llfn(llfn, llvm::AttributePlace::Argument(i), &[byval]);
                 }
-                PassMode::Direct(ref attrs)
-                | PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: false } => {
+                PassMode::Direct(attrs)
+                | PassMode::Indirect { attrs, extra_attrs: None, on_stack: false } => {
                     apply(attrs);
                 }
-                PassMode::Indirect { ref attrs, extra_attrs: Some(ref extra_attrs), on_stack } => {
+                PassMode::Indirect { attrs, extra_attrs: Some(extra_attrs), on_stack } => {
                     assert!(!on_stack);
                     apply(attrs);
                     apply(extra_attrs);
                 }
-                PassMode::Pair(ref a, ref b) => {
+                PassMode::Pair(a, b) => {
                     apply(a);
                     apply(b);
                 }
@@ -488,11 +488,11 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             i += 1;
             i - 1
         };
-        match self.ret.mode {
-            PassMode::Direct(ref attrs) => {
+        match &self.ret.mode {
+            PassMode::Direct(attrs) => {
                 attrs.apply_attrs_to_callsite(llvm::AttributePlace::ReturnValue, bx.cx, callsite);
             }
-            PassMode::Indirect { ref attrs, extra_attrs: _, on_stack } => {
+            PassMode::Indirect { attrs, extra_attrs: _, on_stack } => {
                 assert!(!on_stack);
                 let i = apply(bx.cx, attrs);
                 let sret = llvm::CreateStructRetAttr(bx.cx.llcx, self.ret.layout.llvm_type(bx));
@@ -521,9 +521,9 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             if arg.pad.is_some() {
                 apply(bx.cx, &ArgAttributes::new());
             }
-            match arg.mode {
+            match &arg.mode {
                 PassMode::Ignore => {}
-                PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: true } => {
+                PassMode::Indirect { attrs, extra_attrs: None, on_stack: true } => {
                     let i = apply(bx.cx, attrs);
                     let byval = llvm::CreateByValAttr(bx.cx.llcx, arg.layout.llvm_type(bx));
                     attributes::apply_to_callsite(
@@ -532,19 +532,15 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
                         &[byval],
                     );
                 }
-                PassMode::Direct(ref attrs)
-                | PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: false } => {
+                PassMode::Direct(attrs)
+                | PassMode::Indirect { attrs, extra_attrs: None, on_stack: false } => {
                     apply(bx.cx, attrs);
                 }
-                PassMode::Indirect {
-                    ref attrs,
-                    extra_attrs: Some(ref extra_attrs),
-                    on_stack: _,
-                } => {
+                PassMode::Indirect { attrs, extra_attrs: Some(extra_attrs), on_stack: _ } => {
                     apply(bx.cx, attrs);
                     apply(bx.cx, extra_attrs);
                 }
-                PassMode::Pair(ref a, ref b) => {
+                PassMode::Pair(a, b) => {
                     apply(bx.cx, a);
                     apply(bx.cx, b);
                 }
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 9f364749287..d46a6dd32c8 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -161,7 +161,7 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
             sym::volatile_load | sym::unaligned_volatile_load => {
                 let tp_ty = substs.type_at(0);
                 let ptr = args[0].immediate();
-                let load = if let PassMode::Cast(ty) = fn_abi.ret.mode {
+                let load = if let PassMode::Cast(ty) = &fn_abi.ret.mode {
                     let llty = ty.llvm_type(self);
                     let ptr = self.pointercast(ptr, self.type_ptr_to(llty));
                     self.volatile_load(llty, ptr)
@@ -374,7 +374,7 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
         };
 
         if !fn_abi.ret.is_ignore() {
-            if let PassMode::Cast(ty) = fn_abi.ret.mode {
+            if let PassMode::Cast(ty) = &fn_abi.ret.mode {
                 let ptr_llty = self.type_ptr_to(ty.llvm_type(self));
                 let ptr = self.pointercast(result.llval, ptr_llty);
                 self.store(llval, ptr, result.align);
diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index 47a40be5d8c..187af47114f 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -324,7 +324,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             bx.unreachable();
             return;
         }
-        let llval = match self.fn_abi.ret.mode {
+        let llval = match &self.fn_abi.ret.mode {
             PassMode::Ignore | PassMode::Indirect { .. } => {
                 bx.ret_void();
                 return;
@@ -360,7 +360,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         llval
                     }
                 };
-                let ty = bx.cast_backend_type(&cast_ty);
+                let ty = bx.cast_backend_type(cast_ty);
                 let addr = bx.pointercast(llslot, bx.type_ptr_to(ty));
                 bx.load(ty, addr, self.fn_abi.ret.layout.align.abi)
             }
@@ -1222,8 +1222,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
         if by_ref && !arg.is_indirect() {
             // Have to load the argument, maybe while casting it.
-            if let PassMode::Cast(ty) = arg.mode {
-                let llty = bx.cast_backend_type(&ty);
+            if let PassMode::Cast(ty) = &arg.mode {
+                let llty = bx.cast_backend_type(ty);
                 let addr = bx.pointercast(llval, bx.type_ptr_to(llty));
                 llval = bx.load(llty, addr, align.min(arg.layout.align.abi));
             } else {
diff --git a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
index 94ac71a4dd2..e11ebdce80f 100644
--- a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
@@ -597,8 +597,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         };
 
         if !fn_abi.ret.is_ignore() {
-            if let PassMode::Cast(ty) = fn_abi.ret.mode {
-                let ptr_llty = bx.type_ptr_to(bx.cast_backend_type(&ty));
+            if let PassMode::Cast(ty) = &fn_abi.ret.mode {
+                let ptr_llty = bx.type_ptr_to(bx.cast_backend_type(ty));
                 let ptr = bx.pointercast(result.llval, ptr_llty);
                 bx.store(llval, ptr, result.align);
             } else {
diff --git a/compiler/rustc_const_eval/src/interpret/terminator.rs b/compiler/rustc_const_eval/src/interpret/terminator.rs
index c8557d172ed..27bb828feac 100644
--- a/compiler/rustc_const_eval/src/interpret/terminator.rs
+++ b/compiler/rustc_const_eval/src/interpret/terminator.rs
@@ -218,7 +218,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // Padding must be fully equal.
         let pad_compat = || caller_abi.pad == callee_abi.pad;
         // When comparing the PassMode, we have to be smart about comparing the attributes.
-        let arg_attr_compat = |a1: ArgAttributes, a2: ArgAttributes| {
+        let arg_attr_compat = |a1: &ArgAttributes, a2: &ArgAttributes| {
             // There's only one regular attribute that matters for the call ABI: InReg.
             // Everything else is things like noalias, dereferencable, nonnull, ...
             // (This also applies to pointee_size, pointee_align.)
@@ -233,7 +233,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             }
             return true;
         };
-        let mode_compat = || match (caller_abi.mode, callee_abi.mode) {
+        let mode_compat = || match (&caller_abi.mode, &callee_abi.mode) {
             (PassMode::Ignore, PassMode::Ignore) => true,
             (PassMode::Direct(a1), PassMode::Direct(a2)) => arg_attr_compat(a1, a2),
             (PassMode::Pair(a1, b1), PassMode::Pair(a2, b2)) => {
diff --git a/compiler/rustc_target/src/abi/call/mod.rs b/compiler/rustc_target/src/abi/call/mod.rs
index ab53ea6101d..d4430b1609b 100644
--- a/compiler/rustc_target/src/abi/call/mod.rs
+++ b/compiler/rustc_target/src/abi/call/mod.rs
@@ -26,7 +26,7 @@ mod x86;
 mod x86_64;
 mod x86_win64;
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
+#[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)]
 pub enum PassMode {
     /// Ignore the argument.
     ///
@@ -42,7 +42,7 @@ pub enum PassMode {
     Pair(ArgAttributes, ArgAttributes),
     /// Pass the argument after casting it, to either
     /// a single uniform or a pair of registers.
-    Cast(CastTarget),
+    Cast(Box<CastTarget>),
     /// Pass the argument indirectly via a hidden pointer.
     /// The `extra_attrs` value, if any, is for the extra data (vtable or length)
     /// which indicates that it refers to an unsized rvalue.
@@ -548,7 +548,7 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
     }
 
     pub fn cast_to<T: Into<CastTarget>>(&mut self, target: T) {
-        self.mode = PassMode::Cast(target.into());
+        self.mode = PassMode::Cast(Box::new(target.into()));
     }
 
     pub fn pad_with(&mut self, reg: Reg) {
@@ -737,6 +737,6 @@ mod size_asserts {
     use super::*;
     use rustc_data_structures::static_assert_size;
     // These are in alphabetical order, which is easy to maintain.
-    static_assert_size!(ArgAbi<'_, usize>, 208);
-    static_assert_size!(FnAbi<'_, usize>, 248);
+    static_assert_size!(ArgAbi<'_, usize>, 72);
+    static_assert_size!(FnAbi<'_, usize>, 112);
 }