Skip inlining if there are normalization issues.

Author: cjgillot

compiler/rustc_mir_transform/src/inline.rs

@@ -1,6 +1,7 @@
 //! Inlining pass for MIR functions
 use crate::deref_separator::deref_finder;
 use rustc_attr::InlineAttr;
+use rustc_const_eval::transform::validate::equal_up_to_regions;
 use rustc_index::bit_set::BitSet;
 use rustc_index::vec::Idx;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
@@ -166,6 +167,45 @@ impl<'tcx> Inliner<'tcx> {
             return Err("failed to normalize callee body");
         };
 
+        // Check call signature compatibility.
+        // Normally, this shouldn't be required, but trait normalization failure can create a
+        // validation ICE.
+        let terminator = caller_body[callsite.block].terminator.as_ref().unwrap();
+        let TerminatorKind::Call { args, destination, .. } = &terminator.kind else { bug!() };
+        let destination_ty = destination.ty(&caller_body.local_decls, self.tcx).ty;
+        let output_type = callee_body.return_ty();
+        if !equal_up_to_regions(self.tcx, self.param_env, output_type, destination_ty) {
+            trace!(?output_type, ?destination_ty);
+            return Err("failed to normalize return type");
+        }
+        if callsite.fn_sig.abi() == Abi::RustCall {
+            let mut args = args.into_iter();
+            let _ = args.next(); // Skip `self` argument.
+            let arg_tuple_ty = args.next().unwrap().ty(&caller_body.local_decls, self.tcx);
+            assert!(args.next().is_none());
+
+            let ty::Tuple(arg_tuple_tys) = arg_tuple_ty.kind() else {
+                bug!("Closure arguments are not passed as a tuple");
+            };
+
+            for (arg_ty, input) in arg_tuple_tys.iter().zip(callee_body.args_iter().skip(1)) {
+                let input_type = callee_body.local_decls[input].ty;
+                if !equal_up_to_regions(self.tcx, self.param_env, arg_ty, input_type) {
+                    trace!(?arg_ty, ?input_type);
+                    return Err("failed to normalize tuple argument type");
+                }
+            }
+        } else {
+            for (arg, input) in args.iter().zip(callee_body.args_iter()) {
+                let input_type = callee_body.local_decls[input].ty;
+                let arg_ty = arg.ty(&caller_body.local_decls, self.tcx);
+                if !equal_up_to_regions(self.tcx, self.param_env, arg_ty, input_type) {
+                    trace!(?arg_ty, ?input_type);
+                    return Err("failed to normalize argument type");
+                }
+            }
+        }
+
         let old_blocks = caller_body.basic_blocks().next_index();
         self.inline_call(caller_body, &callsite, callee_body);
         let new_blocks = old_blocks..caller_body.basic_blocks().next_index();

src/test/mir-opt/inline/caller-with-trivial-bound.rs

@@ -0,0 +1,24 @@
+#![crate_type = "lib"]
+
+pub trait Factory<T> {
+    type Item;
+}
+
+pub struct IntFactory;
+
+impl<T> Factory<T> for IntFactory {
+    type Item = usize;
+}
+
+// EMIT_MIR caller_with_trivial_bound.foo.Inline.diff
+pub fn foo<T>()
+where
+    IntFactory: Factory<T>,
+{
+    let mut x: <IntFactory as Factory<T>>::Item = bar::<T>();
+}
+
+#[inline(always)]
+pub fn bar<T>() -> <IntFactory as Factory<T>>::Item {
+    0usize
+}

src/test/mir-opt/inline/caller_with_trivial_bound.foo.Inline.diff

@@ -0,0 +1,33 @@
+- // MIR for `foo` before Inline
++ // MIR for `foo` after Inline
+  
+  fn foo() -> () {
+      let mut _0: ();                      // return place in scope 0 at $DIR/caller-with-trivial-bound.rs:15:1: 15:1
+      let mut _1: <IntFactory as Factory<T>>::Item; // in scope 0 at $DIR/caller-with-trivial-bound.rs:18:9: 18:14
+      scope 1 {
+          debug x => _1;                   // in scope 1 at $DIR/caller-with-trivial-bound.rs:18:9: 18:14
+      }
+  
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/caller-with-trivial-bound.rs:18:9: 18:14
+          _1 = bar::<T>() -> bb1;          // scope 0 at $DIR/caller-with-trivial-bound.rs:18:51: 18:61
+                                           // mir::Constant
+                                           // + span: $DIR/caller-with-trivial-bound.rs:18:51: 18:59
+                                           // + literal: Const { ty: fn() -> <IntFactory as Factory<T>>::Item {bar::<T>}, val: Value(Scalar(<ZST>)) }
+      }
+  
+      bb1: {
+          _0 = const ();                   // scope 0 at $DIR/caller-with-trivial-bound.rs:17:1: 19:2
+          drop(_1) -> [return: bb2, unwind: bb3]; // scope 0 at $DIR/caller-with-trivial-bound.rs:19:1: 19:2
+      }
+  
+      bb2: {
+          StorageDead(_1);                 // scope 0 at $DIR/caller-with-trivial-bound.rs:19:1: 19:2
+          return;                          // scope 0 at $DIR/caller-with-trivial-bound.rs:19:2: 19:2
+      }
+  
+      bb3 (cleanup): {
+          resume;                          // scope 0 at $DIR/caller-with-trivial-bound.rs:14:1: 19:2
+      }
+  }
+