inliner: Use substs_for_mir_body

Changes from 68965 extended the kind of instances that are being
inlined. For some of those, the `instance_mir` returns a MIR body that
is already expressed in terms of the types found in substitution array,
and doesn't need further substitution.

Use `substs_for_mir_body` to take that into account.

compiler/rustc_codegen_cranelift/src/common.rs

@@ -361,13 +361,11 @@ impl<'tcx, M: Module> FunctionCx<'_, 'tcx, M> {
     where
         T: TypeFoldable<'tcx> + Copy,
     {
-        if let Some(substs) = self.instance.substs_for_mir_body() {
-            self.tcx
-                .subst_and_normalize_erasing_regions(substs, ty::ParamEnv::reveal_all(), value)
-        } else {
-            self.tcx
-                .normalize_erasing_regions(ty::ParamEnv::reveal_all(), *value)
-        }
+        self.instance.subst_mir_and_normalize_erasing_regions(
+            self.tcx,
+            ty::ParamEnv::reveal_all(),
+            value
+        )
     }
 
     pub(crate) fn clif_type(&self, ty: Ty<'tcx>) -> Option<Type> {

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -92,15 +92,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         T: Copy + TypeFoldable<'tcx>,
     {
         debug!("monomorphize: self.instance={:?}", self.instance);
-        if let Some(substs) = self.instance.substs_for_mir_body() {
-            self.cx.tcx().subst_and_normalize_erasing_regions(
-                substs,
-                ty::ParamEnv::reveal_all(),
-                &value,
-            )
-        } else {
-            self.cx.tcx().normalize_erasing_regions(ty::ParamEnv::reveal_all(), *value)
-        }
+        self.instance.subst_mir_and_normalize_erasing_regions(
+            self.cx.tcx(),
+            ty::ParamEnv::reveal_all(),
+            value,
+        )
     }
 }
 

compiler/rustc_middle/src/ty/instance.rs

@@ -1,6 +1,6 @@
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::ty::print::{FmtPrinter, Printer};
-use crate::ty::subst::InternalSubsts;
+use crate::ty::subst::{InternalSubsts, Subst};
 use crate::ty::{self, SubstsRef, Ty, TyCtxt, TypeFoldable};
 use rustc_errors::ErrorReported;
 use rustc_hir::def::Namespace;
@@ -470,10 +470,33 @@ impl<'tcx> Instance<'tcx> {
     /// This function returns `Some(substs)` in the former case and `None` otherwise -- i.e., if
     /// this function returns `None`, then the MIR body does not require substitution during
     /// codegen.
-    pub fn substs_for_mir_body(&self) -> Option<SubstsRef<'tcx>> {
+    fn substs_for_mir_body(&self) -> Option<SubstsRef<'tcx>> {
         if self.def.has_polymorphic_mir_body() { Some(self.substs) } else { None }
     }
 
+    pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: &T) -> T
+    where
+        T: TypeFoldable<'tcx> + Copy,
+    {
+        if let Some(substs) = self.substs_for_mir_body() { v.subst(tcx, substs) } else { *v }
+    }
+
+    pub fn subst_mir_and_normalize_erasing_regions<T>(
+        &self,
+        tcx: TyCtxt<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        v: &T,
+    ) -> T
+    where
+        T: TypeFoldable<'tcx> + Clone,
+    {
+        if let Some(substs) = self.substs_for_mir_body() {
+            tcx.subst_and_normalize_erasing_regions(substs, param_env, v)
+        } else {
+            tcx.normalize_erasing_regions(param_env, v.clone())
+        }
+    }
+
     /// Returns a new `Instance` where generic parameters in `instance.substs` are replaced by
     /// identify parameters if they are determined to be unused in `instance.def`.
     pub fn polymorphize(self, tcx: TyCtxt<'tcx>) -> Self {

compiler/rustc_mir/src/interpret/eval_context.rs

@@ -505,11 +505,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         frame: &Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>,
         value: T,
     ) -> T {
-        if let Some(substs) = frame.instance.substs_for_mir_body() {
-            self.tcx.subst_and_normalize_erasing_regions(substs, self.param_env, &value)
-        } else {
-            self.tcx.normalize_erasing_regions(self.param_env, value)
-        }
+        frame.instance.subst_mir_and_normalize_erasing_regions(*self.tcx, self.param_env, &value)
     }
 
     /// The `substs` are assumed to already be in our interpreter "universe" (param_env).

compiler/rustc_mir/src/monomorphize/collector.rs

@@ -543,11 +543,11 @@ impl<'a, 'tcx> MirNeighborCollector<'a, 'tcx> {
         T: TypeFoldable<'tcx>,
     {
         debug!("monomorphize: self.instance={:?}", self.instance);
-        if let Some(substs) = self.instance.substs_for_mir_body() {
-            self.tcx.subst_and_normalize_erasing_regions(substs, ty::ParamEnv::reveal_all(), &value)
-        } else {
-            self.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), value)
-        }
+        self.instance.subst_mir_and_normalize_erasing_regions(
+            self.tcx,
+            ty::ParamEnv::reveal_all(),
+            &value,
+        )
     }
 }
 

compiler/rustc_mir/src/transform/inline.rs

@@ -6,7 +6,6 @@ use rustc_index::vec::Idx;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
 use rustc_middle::mir::visit::*;
 use rustc_middle::mir::*;
-use rustc_middle::ty::subst::Subst;
 use rustc_middle::ty::{self, ConstKind, Instance, InstanceDef, ParamEnv, Ty, TyCtxt};
 use rustc_span::{hygiene::ExpnKind, ExpnData, Span};
 use rustc_target::spec::abi::Abi;
@@ -128,17 +127,15 @@ impl Inliner<'tcx> {
                 self.tcx.instance_mir(callsite.callee.def)
             };
 
-            let callee_body: &Body<'tcx> = &*callee_body;
-
-            let callee_body = if self.consider_optimizing(callsite, callee_body) {
-                self.tcx.subst_and_normalize_erasing_regions(
-                    &callsite.callee.substs,
-                    self.param_env,
-                    callee_body,
-                )
-            } else {
+            if !self.consider_optimizing(callsite, &callee_body) {
                 continue;
-            };
+            }
+
+            let callee_body = callsite.callee.subst_mir_and_normalize_erasing_regions(
+                self.tcx,
+                self.param_env,
+                callee_body,
+            );
 
             // Copy only unevaluated constants from the callee_body into the caller_body.
             // Although we are only pushing `ConstKind::Unevaluated` consts to
@@ -317,7 +314,7 @@ impl Inliner<'tcx> {
                     work_list.push(target);
                     // If the place doesn't actually need dropping, treat it like
                     // a regular goto.
-                    let ty = place.ty(callee_body, tcx).subst(tcx, callsite.callee.substs).ty;
+                    let ty = callsite.callee.subst_mir(self.tcx, &place.ty(callee_body, tcx).ty);
                     if ty.needs_drop(tcx, self.param_env) {
                         cost += CALL_PENALTY;
                         if let Some(unwind) = unwind {
@@ -379,8 +376,7 @@ impl Inliner<'tcx> {
         let ptr_size = tcx.data_layout.pointer_size.bytes();
 
         for v in callee_body.vars_and_temps_iter() {
-            let v = &callee_body.local_decls[v];
-            let ty = v.ty.subst(tcx, callsite.callee.substs);
+            let ty = callsite.callee.subst_mir(self.tcx, &callee_body.local_decls[v].ty);
             // Cost of the var is the size in machine-words, if we know
             // it.
             if let Some(size) = type_size_of(tcx, self.param_env, ty) {

src/test/mir-opt/inline/inline-shims.rs

@@ -0,0 +1,13 @@
+// ignore-wasm32-bare compiled with panic=abort by default
+#![crate_type = "lib"]
+
+// EMIT_MIR inline_shims.clone.Inline.diff
+pub fn clone<A, B>(f: fn(A, B)) -> fn(A, B) {
+    f.clone()
+}
+
+// EMIT_MIR inline_shims.drop.Inline.diff
+pub fn drop<A, B>(a: *mut Vec<A>, b: *mut Option<B>) {
+    unsafe { std::ptr::drop_in_place(a) }
+    unsafe { std::ptr::drop_in_place(b) }
+}

src/test/mir-opt/inline/inline_shims.clone.Inline.diff

@@ -0,0 +1,26 @@
+- // MIR for `clone` before Inline
++ // MIR for `clone` after Inline
+
+  fn clone(_1: fn(A, B)) -> fn(A, B) {
+      debug f => _1;                       // in scope 0 at $DIR/inline-shims.rs:5:20: 5:21
+      let mut _0: fn(A, B);                // return place in scope 0 at $DIR/inline-shims.rs:5:36: 5:44
+      let mut _2: &fn(A, B);               // in scope 0 at $DIR/inline-shims.rs:6:5: 6:6
++     scope 1 (inlined <fn(A, B) as Clone>::clone - shim(fn(A, B))) { // at $DIR/inline-shims.rs:6:5: 6:14
++     }
+
+      bb0: {
+          StorageLive(_2);                 // scope 0 at $DIR/inline-shims.rs:6:5: 6:6
+          _2 = &_1;                        // scope 0 at $DIR/inline-shims.rs:6:5: 6:6
+-         _0 = <fn(A, B) as Clone>::clone(move _2) -> bb1; // scope 0 at $DIR/inline-shims.rs:6:5: 6:14
+-                                          // mir::Constant
+-                                          // + span: $DIR/inline-shims.rs:6:7: 6:12
+-                                          // + literal: Const { ty: for<'r> fn(&'r fn(A, B)) -> fn(A, B) {<fn(A, B) as std::clone::Clone>::clone}, val: Value(Scalar(<ZST>)) }
+-     }
+- 
+-     bb1: {
++         _0 = (*_2);                      // scope 1 at $DIR/inline-shims.rs:6:5: 6:14
+          StorageDead(_2);                 // scope 0 at $DIR/inline-shims.rs:6:13: 6:14
+          return;                          // scope 0 at $DIR/inline-shims.rs:7:2: 7:2
+      }
+  }
+

src/test/mir-opt/inline/inline_shims.drop.Inline.diff

@@ -0,0 +1,52 @@
+- // MIR for `drop` before Inline
++ // MIR for `drop` after Inline
+
+  fn drop(_1: *mut Vec<A>, _2: *mut Option<B>) -> () {
+      debug a => _1;                       // in scope 0 at $DIR/inline-shims.rs:10:19: 10:20
+      debug b => _2;                       // in scope 0 at $DIR/inline-shims.rs:10:35: 10:36
+      let mut _0: ();                      // return place in scope 0 at $DIR/inline-shims.rs:10:54: 10:54
+      let _3: ();                          // in scope 0 at $DIR/inline-shims.rs:11:14: 11:40
+      let mut _4: *mut std::vec::Vec<A>;   // in scope 0 at $DIR/inline-shims.rs:11:38: 11:39
+      let mut _5: *mut std::option::Option<B>; // in scope 0 at $DIR/inline-shims.rs:12:38: 12:39
+      scope 1 {
+      }
+      scope 2 {
++         scope 3 (inlined drop_in_place::<Option<B>> - shim(Some(Option<B>))) { // at $DIR/inline-shims.rs:12:14: 12:40
++             let mut _6: isize;           // in scope 3 at $DIR/inline-shims.rs:12:14: 12:40
++             let mut _7: isize;           // in scope 3 at $DIR/inline-shims.rs:12:14: 12:40
++         }
+      }
+
+      bb0: {
+          StorageLive(_3);                 // scope 0 at $DIR/inline-shims.rs:11:5: 11:42
+          StorageLive(_4);                 // scope 1 at $DIR/inline-shims.rs:11:38: 11:39
+          _4 = _1;                         // scope 1 at $DIR/inline-shims.rs:11:38: 11:39
+          _3 = drop_in_place::<Vec<A>>(move _4) -> bb1; // scope 1 at $DIR/inline-shims.rs:11:14: 11:40
+                                           // mir::Constant
+                                           // + span: $DIR/inline-shims.rs:11:14: 11:37
+                                           // + literal: Const { ty: unsafe fn(*mut std::vec::Vec<A>) {std::intrinsics::drop_in_place::<std::vec::Vec<A>>}, val: Value(Scalar(<ZST>)) }
+      }
+
+      bb1: {
+          StorageDead(_4);                 // scope 1 at $DIR/inline-shims.rs:11:39: 11:40
+          StorageDead(_3);                 // scope 0 at $DIR/inline-shims.rs:11:41: 11:42
+          StorageLive(_5);                 // scope 2 at $DIR/inline-shims.rs:12:38: 12:39
+          _5 = _2;                         // scope 2 at $DIR/inline-shims.rs:12:38: 12:39
+-         _0 = drop_in_place::<Option<B>>(move _5) -> bb2; // scope 2 at $DIR/inline-shims.rs:12:14: 12:40
+-                                          // mir::Constant
+-                                          // + span: $DIR/inline-shims.rs:12:14: 12:37
+-                                          // + literal: Const { ty: unsafe fn(*mut std::option::Option<B>) {std::intrinsics::drop_in_place::<std::option::Option<B>>}, val: Value(Scalar(<ZST>)) }
++         _6 = discriminant((*_5));        // scope 3 at $DIR/inline-shims.rs:12:14: 12:40
++         switchInt(move _6) -> [0_isize: bb2, otherwise: bb3]; // scope 3 at $DIR/inline-shims.rs:12:14: 12:40
+      }
+
+      bb2: {
+          StorageDead(_5);                 // scope 2 at $DIR/inline-shims.rs:12:39: 12:40
+          return;                          // scope 0 at $DIR/inline-shims.rs:13:2: 13:2
++     }
++ 
++     bb3: {
++         drop((((*_5) as Some).0: B)) -> bb2; // scope 3 at $DIR/inline-shims.rs:12:14: 12:40
+      }
+  }
+