Issue 149164 fix

compiler/rustc_codegen_llvm/src/builder/autodiff.rs

@@ -4,7 +4,7 @@ use rustc_ast::expand::autodiff_attrs::{AutoDiffAttrs, DiffActivity, DiffMode};
 use rustc_ast::expand::typetree::FncTree;
 use rustc_codegen_ssa::common::TypeKind;
 use rustc_codegen_ssa::traits::{BaseTypeCodegenMethods, BuilderMethods};
-use rustc_middle::ty::{Instance, PseudoCanonicalInput, TyCtxt, TypingEnv};
+use rustc_middle::ty::{PseudoCanonicalInput, Ty, TyCtxt, TypingEnv};
 use rustc_middle::{bug, ty};
 use rustc_target::callconv::PassMode;
 use tracing::debug;
@@ -16,25 +16,23 @@ use crate::llvm::{self, TRUE, Type, Value};
 
 pub(crate) fn adjust_activity_to_abi<'tcx>(
     tcx: TyCtxt<'tcx>,
-    instance: Instance<'tcx>,
+    fn_ptr_ty: Ty<'tcx>,
     typing_env: TypingEnv<'tcx>,
     da: &mut Vec<DiffActivity>,
 ) {
-    let fn_ty = instance.ty(tcx, typing_env);
-
-    if !matches!(fn_ty.kind(), ty::FnDef(..)) {
-        bug!("expected fn def for autodiff, got {:?}", fn_ty);
+    if !matches!(fn_ptr_ty.kind(), ty::FnPtr(..)) {
+        bug!("expected fn ptr for autodiff, got {:?}", fn_ptr_ty);
     }
 
     // We don't actually pass the types back into the type system.
     // All we do is decide how to handle the arguments.
-    let sig = fn_ty.fn_sig(tcx).skip_binder();
+    let poly_sig = fn_ptr_ty.fn_sig(tcx);
+    let sig = poly_sig.skip_binder();
 
     // FIXME(Sa4dUs): pass proper varargs once we have support for differentiating variadic functions
-    let Ok(fn_abi) =
-        tcx.fn_abi_of_instance(typing_env.as_query_input((instance, ty::List::empty())))
-    else {
-        bug!("failed to get fn_abi of instance with empty varargs");
+    let pci = PseudoCanonicalInput { typing_env, value: (poly_sig, ty::List::empty()) };
+    let Ok(fn_abi) = tcx.fn_abi_of_fn_ptr(pci) else {
+        bug!("failed to get fn_abi of fn_ptr with empty varargs");
     };
 
     let mut new_activities = vec![];

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -1229,9 +1229,13 @@ fn codegen_autodiff<'ll, 'tcx>(
         bug!("could not find autodiff attrs")
     };
 
+    let fn_ty = fn_source.ty(tcx, TypingEnv::fully_monomorphized());
+    let fn_sig = fn_ty.fn_sig(tcx);
+    let fn_ptr_ty = Ty::new_fn_ptr(tcx, fn_sig);
+
     adjust_activity_to_abi(
         tcx,
-        fn_source,
+        fn_ptr_ty,
         TypingEnv::fully_monomorphized(),
         &mut diff_attrs.input_activity,
     );