diff --git a/src/abi/mod.rs b/src/abi/mod.rs
index 199fa6861cf..eddb479073c 100644
--- a/src/abi/mod.rs
+++ b/src/abi/mod.rs
@@ -70,7 +70,7 @@ pub(crate) fn get_function_sig<'tcx>(
     default_call_conv: CallConv,
     inst: Instance<'tcx>,
 ) -> Signature {
-    assert!(!inst.substs.has_infer());
+    assert!(!inst.args.has_infer());
     clif_sig_from_fn_abi(
         tcx,
         default_call_conv,
@@ -377,16 +377,16 @@ pub(crate) fn codegen_terminator_call<'tcx>(
     let ret_place = codegen_place(fx, destination);
 
     // Handle special calls like intrinsics and empty drop glue.
-    let instance = if let ty::FnDef(def_id, substs) = *func.layout().ty.kind() {
+    let instance = if let ty::FnDef(def_id, fn_args) = *func.layout().ty.kind() {
         let instance =
-            ty::Instance::expect_resolve(fx.tcx, ty::ParamEnv::reveal_all(), def_id, substs)
+            ty::Instance::expect_resolve(fx.tcx, ty::ParamEnv::reveal_all(), def_id, fn_args)
                 .polymorphize(fx.tcx);
 
         if fx.tcx.symbol_name(instance).name.starts_with("llvm.") {
             crate::intrinsics::codegen_llvm_intrinsic_call(
                 fx,
                 &fx.tcx.symbol_name(instance).name,
-                substs,
+                fn_args,
                 args,
                 ret_place,
                 target,
@@ -611,7 +611,7 @@ pub(crate) fn codegen_drop<'tcx>(
                 // `Instance::resolve_drop_in_place`?
                 let virtual_drop = Instance {
                     def: ty::InstanceDef::Virtual(drop_instance.def_id(), 0),
-                    substs: drop_instance.substs,
+                    args: drop_instance.args,
                 };
                 let fn_abi =
                     RevealAllLayoutCx(fx.tcx).fn_abi_of_instance(virtual_drop, ty::List::empty());
@@ -648,7 +648,7 @@ pub(crate) fn codegen_drop<'tcx>(
 
                 let virtual_drop = Instance {
                     def: ty::InstanceDef::Virtual(drop_instance.def_id(), 0),
-                    substs: drop_instance.substs,
+                    args: drop_instance.args,
                 };
                 let fn_abi =
                     RevealAllLayoutCx(fx.tcx).fn_abi_of_instance(virtual_drop, ty::List::empty());
diff --git a/src/base.rs b/src/base.rs
index 334b2780b49..e05f2146f0c 100644
--- a/src/base.rs
+++ b/src/base.rs
@@ -28,7 +28,7 @@ pub(crate) fn codegen_fn<'tcx>(
     module: &mut dyn Module,
     instance: Instance<'tcx>,
 ) -> CodegenedFunction {
-    debug_assert!(!instance.substs.has_infer());
+    debug_assert!(!instance.args.has_infer());
 
     let symbol_name = tcx.symbol_name(instance).name.to_string();
     let _timer = tcx.prof.generic_activity_with_arg("codegen fn", &*symbol_name);
@@ -578,13 +578,13 @@ fn codegen_stmt<'tcx>(
                     let from_ty = fx.monomorphize(operand.ty(&fx.mir.local_decls, fx.tcx));
                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
                     match *from_ty.kind() {
-                        ty::FnDef(def_id, substs) => {
+                        ty::FnDef(def_id, args) => {
                             let func_ref = fx.get_function_ref(
                                 Instance::resolve_for_fn_ptr(
                                     fx.tcx,
                                     ParamEnv::reveal_all(),
                                     def_id,
-                                    substs,
+                                    args,
                                 )
                                 .unwrap()
                                 .polymorphize(fx.tcx),
@@ -668,11 +668,11 @@ fn codegen_stmt<'tcx>(
                 ) => {
                     let operand = codegen_operand(fx, operand);
                     match *operand.layout().ty.kind() {
-                        ty::Closure(def_id, substs) => {
+                        ty::Closure(def_id, args) => {
                             let instance = Instance::resolve_closure(
                                 fx.tcx,
                                 def_id,
-                                substs,
+                                args,
                                 ty::ClosureKind::FnOnce,
                             )
                             .expect("failed to normalize and resolve closure during codegen")
diff --git a/src/constant.rs b/src/constant.rs
index 427340c333e..c3153574295 100644
--- a/src/constant.rs
+++ b/src/constant.rs
@@ -57,7 +57,7 @@ pub(crate) fn codegen_tls_ref<'tcx>(
     let tls_ptr = if !def_id.is_local() && fx.tcx.needs_thread_local_shim(def_id) {
         let instance = ty::Instance {
             def: ty::InstanceDef::ThreadLocalShim(def_id),
-            substs: ty::InternalSubsts::empty(),
+            args: ty::GenericArgs::empty(),
         };
         let func_ref = fx.get_function_ref(instance);
         let call = fx.bcx.ins().call(func_ref, &[]);
diff --git a/src/global_asm.rs b/src/global_asm.rs
index 63a1f6959dd..baadd7a9e81 100644
--- a/src/global_asm.rs
+++ b/src/global_asm.rs
@@ -42,7 +42,7 @@ pub(crate) fn codegen_global_asm_item(tcx: TyCtxt<'_>, global_asm: &mut String,
                         InlineAsmOperand::SymFn { anon_const } => {
                             let ty = tcx.typeck_body(anon_const.body).node_type(anon_const.hir_id);
                             let instance = match ty.kind() {
-                                &ty::FnDef(def_id, substs) => Instance::new(def_id, substs),
+                                &ty::FnDef(def_id, args) => Instance::new(def_id, args),
                                 _ => span_bug!(op_sp, "asm sym is not a function"),
                             };
                             let symbol = tcx.symbol_name(instance);
diff --git a/src/inline_asm.rs b/src/inline_asm.rs
index 3ba530c040f..518e3da07a4 100644
--- a/src/inline_asm.rs
+++ b/src/inline_asm.rs
@@ -254,12 +254,12 @@ pub(crate) fn codegen_inline_asm<'tcx>(
             }
             InlineAsmOperand::SymFn { ref value } => {
                 let literal = fx.monomorphize(value.literal);
-                if let ty::FnDef(def_id, substs) = *literal.ty().kind() {
+                if let ty::FnDef(def_id, args) = *literal.ty().kind() {
                     let instance = ty::Instance::resolve_for_fn_ptr(
                         fx.tcx,
                         ty::ParamEnv::reveal_all(),
                         def_id,
-                        substs,
+                        args,
                     )
                     .unwrap();
                     let symbol = fx.tcx.symbol_name(instance);
diff --git a/src/intrinsics/llvm.rs b/src/intrinsics/llvm.rs
index f67fdb59270..63b5402f2b6 100644
--- a/src/intrinsics/llvm.rs
+++ b/src/intrinsics/llvm.rs
@@ -3,23 +3,35 @@
 use crate::intrinsics::*;
 use crate::prelude::*;
 
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 
 pub(crate) fn codegen_llvm_intrinsic_call<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     intrinsic: &str,
-    substs: SubstsRef<'tcx>,
+    generic_args: GenericArgsRef<'tcx>,
     args: &[mir::Operand<'tcx>],
     ret: CPlace<'tcx>,
     target: Option<BasicBlock>,
 ) {
     if intrinsic.starts_with("llvm.aarch64") {
         return llvm_aarch64::codegen_aarch64_llvm_intrinsic_call(
-            fx, intrinsic, substs, args, ret, target,
+            fx,
+            intrinsic,
+            generic_args,
+            args,
+            ret,
+            target,
         );
     }
     if intrinsic.starts_with("llvm.x86") {
-        return llvm_x86::codegen_x86_llvm_intrinsic_call(fx, intrinsic, substs, args, ret, target);
+        return llvm_x86::codegen_x86_llvm_intrinsic_call(
+            fx,
+            intrinsic,
+            generic_args,
+            args,
+            ret,
+            target,
+        );
     }
 
     match intrinsic {
diff --git a/src/intrinsics/llvm_aarch64.rs b/src/intrinsics/llvm_aarch64.rs
index 33b2f4702a7..c20a9915930 100644
--- a/src/intrinsics/llvm_aarch64.rs
+++ b/src/intrinsics/llvm_aarch64.rs
@@ -3,12 +3,12 @@
 use crate::intrinsics::*;
 use crate::prelude::*;
 
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 
 pub(crate) fn codegen_aarch64_llvm_intrinsic_call<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     intrinsic: &str,
-    _substs: SubstsRef<'tcx>,
+    _args: GenericArgsRef<'tcx>,
     args: &[mir::Operand<'tcx>],
     ret: CPlace<'tcx>,
     target: Option<BasicBlock>,
diff --git a/src/intrinsics/llvm_x86.rs b/src/intrinsics/llvm_x86.rs
index 24ad0083a22..18162fb5ab2 100644
--- a/src/intrinsics/llvm_x86.rs
+++ b/src/intrinsics/llvm_x86.rs
@@ -3,12 +3,12 @@
 use crate::intrinsics::*;
 use crate::prelude::*;
 
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 
 pub(crate) fn codegen_x86_llvm_intrinsic_call<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     intrinsic: &str,
-    _substs: SubstsRef<'tcx>,
+    _args: GenericArgsRef<'tcx>,
     args: &[mir::Operand<'tcx>],
     ret: CPlace<'tcx>,
     target: Option<BasicBlock>,
diff --git a/src/intrinsics/mod.rs b/src/intrinsics/mod.rs
index 5862f18299e..da8ab361331 100644
--- a/src/intrinsics/mod.rs
+++ b/src/intrinsics/mod.rs
@@ -24,7 +24,7 @@ pub(crate) use llvm::codegen_llvm_intrinsic_call;
 use rustc_middle::ty;
 use rustc_middle::ty::layout::{HasParamEnv, ValidityRequirement};
 use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_span::symbol::{kw, sym, Symbol};
 
 use crate::prelude::*;
@@ -213,13 +213,13 @@ pub(crate) fn codegen_intrinsic_call<'tcx>(
     source_info: mir::SourceInfo,
 ) {
     let intrinsic = fx.tcx.item_name(instance.def_id());
-    let substs = instance.substs;
+    let instance_args = instance.args;
 
     if intrinsic.as_str().starts_with("simd_") {
         self::simd::codegen_simd_intrinsic_call(
             fx,
             intrinsic,
-            substs,
+            instance_args,
             args,
             destination,
             target.expect("target for simd intrinsic"),
@@ -233,7 +233,7 @@ pub(crate) fn codegen_intrinsic_call<'tcx>(
             fx,
             instance,
             intrinsic,
-            substs,
+            instance_args,
             args,
             destination,
             target,
@@ -365,7 +365,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     instance: Instance<'tcx>,
     intrinsic: Symbol,
-    substs: SubstsRef<'tcx>,
+    generic_args: GenericArgsRef<'tcx>,
     args: &[mir::Operand<'tcx>],
     ret: CPlace<'tcx>,
     destination: Option<BasicBlock>,
@@ -394,7 +394,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let dst = dst.load_scalar(fx);
             let count = count.load_scalar(fx);
 
-            let elem_ty = substs.type_at(0);
+            let elem_ty = generic_args.type_at(0);
             let elem_size: u64 = fx.layout_of(elem_ty).size.bytes();
             assert_eq!(args.len(), 3);
             let byte_amount =
@@ -410,7 +410,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let src = src.load_scalar(fx);
             let count = count.load_scalar(fx);
 
-            let elem_ty = substs.type_at(0);
+            let elem_ty = generic_args.type_at(0);
             let elem_size: u64 = fx.layout_of(elem_ty).size.bytes();
             assert_eq!(args.len(), 3);
             let byte_amount =
@@ -428,7 +428,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
         sym::size_of_val => {
             intrinsic_args!(fx, args => (ptr); intrinsic);
 
-            let layout = fx.layout_of(substs.type_at(0));
+            let layout = fx.layout_of(generic_args.type_at(0));
             // Note: Can't use is_unsized here as truly unsized types need to take the fixed size
             // branch
             let size = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
@@ -443,7 +443,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
         sym::min_align_of_val => {
             intrinsic_args!(fx, args => (ptr); intrinsic);
 
-            let layout = fx.layout_of(substs.type_at(0));
+            let layout = fx.layout_of(generic_args.type_at(0));
             // Note: Can't use is_unsized here as truly unsized types need to take the fixed size
             // branch
             let align = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
@@ -602,7 +602,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
         sym::assert_inhabited | sym::assert_zero_valid | sym::assert_mem_uninitialized_valid => {
             intrinsic_args!(fx, args => (); intrinsic);
 
-            let ty = substs.type_at(0);
+            let ty = generic_args.type_at(0);
 
             let requirement = ValidityRequirement::from_intrinsic(intrinsic);
 
@@ -674,7 +674,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             intrinsic_args!(fx, args => (ptr, base); intrinsic);
             let ptr = ptr.load_scalar(fx);
             let base = base.load_scalar(fx);
-            let ty = substs.type_at(0);
+            let ty = generic_args.type_at(0);
 
             let pointee_size: u64 = fx.layout_of(ty).size.bytes();
             let diff_bytes = fx.bcx.ins().isub(ptr, base);
@@ -720,7 +720,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             intrinsic_args!(fx, args => (ptr); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
-            let ty = substs.type_at(0);
+            let ty = generic_args.type_at(0);
             match ty.kind() {
                 ty::Uint(UintTy::U128) | ty::Int(IntTy::I128) => {
                     // FIXME implement 128bit atomics
@@ -751,7 +751,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             intrinsic_args!(fx, args => (ptr, val); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
-            let ty = substs.type_at(0);
+            let ty = generic_args.type_at(0);
             match ty.kind() {
                 ty::Uint(UintTy::U128) | ty::Int(IntTy::I128) => {
                     // FIXME implement 128bit atomics
@@ -1128,7 +1128,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let lhs_ref = lhs_ref.load_scalar(fx);
             let rhs_ref = rhs_ref.load_scalar(fx);
 
-            let size = fx.layout_of(substs.type_at(0)).layout.size();
+            let size = fx.layout_of(generic_args.type_at(0)).layout.size();
             // FIXME add and use emit_small_memcmp
             let is_eq_value = if size == Size::ZERO {
                 // No bytes means they're trivially equal
diff --git a/src/intrinsics/simd.rs b/src/intrinsics/simd.rs
index 6741362e8b6..d1c29f24ab9 100644
--- a/src/intrinsics/simd.rs
+++ b/src/intrinsics/simd.rs
@@ -1,6 +1,6 @@
 //! Codegen `extern "platform-intrinsic"` intrinsics.
 
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_span::Symbol;
 use rustc_target::abi::Endian;
 
@@ -21,7 +21,7 @@ fn report_simd_type_validation_error(
 pub(super) fn codegen_simd_intrinsic_call<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     intrinsic: Symbol,
-    _substs: SubstsRef<'tcx>,
+    _args: GenericArgsRef<'tcx>,
     args: &[mir::Operand<'tcx>],
     ret: CPlace<'tcx>,
     target: BasicBlock,
diff --git a/src/main_shim.rs b/src/main_shim.rs
index 20ba73f3852..b5efe44d8b3 100644
--- a/src/main_shim.rs
+++ b/src/main_shim.rs
@@ -1,6 +1,6 @@
 use rustc_hir::LangItem;
-use rustc_middle::ty::subst::GenericArg;
 use rustc_middle::ty::AssocKind;
+use rustc_middle::ty::GenericArg;
 use rustc_session::config::{sigpipe, EntryFnType};
 use rustc_span::symbol::Ident;
 
@@ -119,7 +119,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                     tcx,
                     ParamEnv::reveal_all(),
                     report.def_id,
-                    tcx.mk_substs(&[GenericArg::from(main_ret_ty)]),
+                    tcx.mk_args(&[GenericArg::from(main_ret_ty)]),
                 )
                 .unwrap()
                 .unwrap()
@@ -146,7 +146,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                     tcx,
                     ParamEnv::reveal_all(),
                     start_def_id,
-                    tcx.mk_substs(&[main_ret_ty.into()]),
+                    tcx.mk_args(&[main_ret_ty.into()]),
                 )
                 .unwrap()
                 .unwrap()
diff --git a/src/pretty_clif.rs b/src/pretty_clif.rs
index 5a4f9e80445..0ead50c34ea 100644
--- a/src/pretty_clif.rs
+++ b/src/pretty_clif.rs
@@ -9,7 +9,7 @@
 //!
 //! function u0:22(i64) -> i8, i8 system_v {
 //! ; symbol _ZN97_$LT$example..IsNotEmpty$u20$as$u20$mini_core..FnOnce$LT$$LP$$RF$$RF$$u5b$u16$u5d$$C$$RP$$GT$$GT$9call_once17hd517c453d67c0915E
-//! ; instance Instance { def: Item(WithOptConstParam { did: DefId(0:42 ~ example[4e51]::{impl#0}::call_once), const_param_did: None }), substs: [ReErased, ReErased] }
+//! ; instance Instance { def: Item(WithOptConstParam { did: DefId(0:42 ~ example[4e51]::{impl#0}::call_once), const_param_did: None }), args: [ReErased, ReErased] }
 //! ; abi FnAbi { args: [ArgAbi { layout: TyAndLayout { ty: IsNotEmpty, layout: Layout { size: Size(0 bytes), align: AbiAndPrefAlign { abi: Align(1 bytes), pref: Align(8 bytes) }, abi: Aggregate { sized: true }, fields: Arbitrary { offsets: [], memory_index: [] }, largest_niche: None, variants: Single { index: 0 } } }, mode: Ignore }, ArgAbi { layout: TyAndLayout { ty: &&[u16], layout: Layout { size: Size(8 bytes), align: AbiAndPrefAlign { abi: Align(8 bytes), pref: Align(8 bytes) }, abi: Scalar(Initialized { value: Pointer(AddressSpace(0)), valid_range: 1..=18446744073709551615 }), fields: Primitive, largest_niche: Some(Niche { offset: Size(0 bytes), value: Pointer(AddressSpace(0)), valid_range: 1..=18446744073709551615 }), variants: Single { index: 0 } } }, mode: Direct(ArgAttributes { regular: NonNull | NoUndef, arg_ext: None, pointee_size: Size(0 bytes), pointee_align: Some(Align(8 bytes)) }) }], ret: ArgAbi { layout: TyAndLayout { ty: (u8, u8), layout: Layout { size: Size(2 bytes), align: AbiAndPrefAlign { abi: Align(1 bytes), pref: Align(8 bytes) }, abi: ScalarPair(Initialized { value: Int(I8, false), valid_range: 0..=255 }, Initialized { value: Int(I8, false), valid_range: 0..=255 }), fields: Arbitrary { offsets: [Size(0 bytes), Size(1 bytes)], memory_index: [0, 1] }, largest_niche: None, variants: Single { index: 0 } } }, mode: Pair(ArgAttributes { regular: NoUndef, arg_ext: None, pointee_size: Size(0 bytes), pointee_align: None }, ArgAttributes { regular: NoUndef, arg_ext: None, pointee_size: Size(0 bytes), pointee_align: None }) }, c_variadic: false, fixed_count: 1, conv: Rust, can_unwind: false }
 //!
 //! ; kind  loc.idx   param    pass mode                            ty
@@ -25,7 +25,7 @@
 //!
 //!     ss0 = explicit_slot 16
 //!     sig0 = (i64, i64) -> i8, i8 system_v
-//!     fn0 = colocated u0:23 sig0 ; Instance { def: Item(WithOptConstParam { did: DefId(0:46 ~ example[4e51]::{impl#1}::call_mut), const_param_did: None }), substs: [ReErased, ReErased] }
+//!     fn0 = colocated u0:23 sig0 ; Instance { def: Item(WithOptConstParam { did: DefId(0:46 ~ example[4e51]::{impl#1}::call_mut), const_param_did: None }), args: [ReErased, ReErased] }
 //!
 //! block0(v0: i64):
 //!     nop
@@ -261,7 +261,7 @@ pub(crate) fn write_clif_file(
 
 impl fmt::Debug for FunctionCx<'_, '_, '_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        writeln!(f, "{:?}", self.instance.substs)?;
+        writeln!(f, "{:?}", self.instance.args)?;
         writeln!(f, "{:?}", self.local_map)?;
 
         let mut clif = String::new();
diff --git a/src/value_and_place.rs b/src/value_and_place.rs
index 133c989b686..ec0b61a7ce5 100644
--- a/src/value_and_place.rs
+++ b/src/value_and_place.rs
@@ -850,11 +850,11 @@ pub(crate) fn assert_assignable<'tcx>(
                 }
             }
         }
-        (&ty::Adt(adt_def_a, substs_a), &ty::Adt(adt_def_b, substs_b))
+        (&ty::Adt(adt_def_a, args_a), &ty::Adt(adt_def_b, args_b))
             if adt_def_a.did() == adt_def_b.did() =>
         {
-            let mut types_a = substs_a.types();
-            let mut types_b = substs_b.types();
+            let mut types_a = args_a.types();
+            let mut types_b = args_b.types();
             loop {
                 match (types_a.next(), types_b.next()) {
                     (Some(a), Some(b)) => assert_assignable(fx, a, b, limit - 1),
@@ -864,11 +864,11 @@ pub(crate) fn assert_assignable<'tcx>(
             }
         }
         (ty::Array(a, _), ty::Array(b, _)) => assert_assignable(fx, *a, *b, limit - 1),
-        (&ty::Closure(def_id_a, substs_a), &ty::Closure(def_id_b, substs_b))
+        (&ty::Closure(def_id_a, args_a), &ty::Closure(def_id_b, args_b))
             if def_id_a == def_id_b =>
         {
-            let mut types_a = substs_a.types();
-            let mut types_b = substs_b.types();
+            let mut types_a = args_a.types();
+            let mut types_b = args_b.types();
             loop {
                 match (types_a.next(), types_b.next()) {
                     (Some(a), Some(b)) => assert_assignable(fx, a, b, limit - 1),