diff --git a/compiler/rustc_monomorphize/src/partitioning/autodiff.rs b/compiler/rustc_monomorphize/src/partitioning/autodiff.rs
index 22d593b80b895..9f6bcf18e8943 100644
--- a/compiler/rustc_monomorphize/src/partitioning/autodiff.rs
+++ b/compiler/rustc_monomorphize/src/partitioning/autodiff.rs
@@ -1,3 +1,4 @@
+use rustc_abi::HasDataLayout;
 use rustc_ast::expand::autodiff_attrs::{AutoDiffItem, DiffActivity};
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::bug;
@@ -16,6 +17,7 @@ fn adjust_activity_to_abi<'tcx>(tcx: TyCtxt<'tcx>, fn_ty: Ty<'tcx>, da: &mut Vec
     // 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 pointer_size = tcx.data_layout().pointer_size;
 
     let mut new_activities = vec![];
     let mut new_positions = vec![];
@@ -70,6 +72,25 @@ fn adjust_activity_to_abi<'tcx>(tcx: TyCtxt<'tcx>, fn_ty: Ty<'tcx>, da: &mut Vec
                 continue;
             }
         }
+
+        let pci = PseudoCanonicalInput { typing_env: TypingEnv::fully_monomorphized(), value: *ty };
+
+        let layout = match tcx.layout_of(pci) {
+            Ok(layout) => layout.layout,
+            Err(_) => {
+                bug!("failed to compute layout for type {:?}", ty);
+            }
+        };
+
+        let is_product = |t: Ty<'tcx>| matches!(t.kind(), ty::Tuple(_) | ty::Adt(_, _));
+
+        if layout.size() <= pointer_size * 2 && is_product(*ty) {
+            let n_scalars = count_scalar_fields(tcx, *ty);
+            for _ in 0..n_scalars.saturating_sub(1) {
+                new_activities.push(da[i].clone());
+                new_positions.push(i + 1);
+            }
+        }
     }
     // now add the extra activities coming from slices
     // Reverse order to not invalidate the indices
@@ -80,6 +101,20 @@ fn adjust_activity_to_abi<'tcx>(tcx: TyCtxt<'tcx>, fn_ty: Ty<'tcx>, da: &mut Vec
     }
 }
 
+fn count_scalar_fields<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> usize {
+    match ty.kind() {
+        ty::Float(_) | ty::Int(_) | ty::Uint(_) => 1,
+        ty::Adt(def, substs) if def.is_struct() => def
+            .non_enum_variant()
+            .fields
+            .iter()
+            .map(|f| count_scalar_fields(tcx, f.ty(tcx, substs)))
+            .sum(),
+        ty::Tuple(substs) => substs.iter().map(|t| count_scalar_fields(tcx, t)).sum(),
+        _ => 0,
+    }
+}
+
 pub(crate) fn find_autodiff_source_functions<'tcx>(
     tcx: TyCtxt<'tcx>,
     usage_map: &UsageMap<'tcx>,
diff --git a/tests/codegen/autodiff/abi_handling.rs b/tests/codegen/autodiff/abi_handling.rs
new file mode 100644
index 0000000000000..4f6cb575a00b4
--- /dev/null
+++ b/tests/codegen/autodiff/abi_handling.rs
@@ -0,0 +1,263 @@
+//@ revisions: debug release
+
+//@[debug] compile-flags: -Zautodiff=Enable -C opt-level=0 -Clto=fat
+//@[release] compile-flags: -Zautodiff=Enable -C opt-level=3 -Clto=fat
+//@ no-prefer-dynamic
+//@ needs-enzyme
+
+// This does only test the funtion attribute handling for autodiff.
+// Function argument changes are troublesome for Enzyme, so we have to
+// ensure that arguments remain the same, or if we change them, be aware
+// of the changes to handle it correctly.
+
+#![feature(autodiff)]
+
+use std::autodiff::{autodiff_forward, autodiff_reverse};
+
+#[derive(Copy, Clone)]
+struct Input {
+    x: f32,
+    y: f32,
+}
+
+#[derive(Copy, Clone)]
+struct Wrapper {
+    z: f32,
+}
+
+#[derive(Copy, Clone)]
+struct NestedInput {
+    x: f32,
+    y: Wrapper,
+}
+
+fn square(x: f32) -> f32 {
+    x * x
+}
+
+// CHECK: ; abi_handling::f1
+// CHECK-NEXT: ; Function Attrs: {{.*}}noinline{{.*}}
+// debug-NEXT: define internal float @_ZN12abi_handling2f117h536ac8081c1e4101E(ptr align 4 %x)
+// release-NEXT: define internal fastcc noundef float @_ZN12abi_handling2f117h536ac8081c1e4101E(float %x.0.val, float %x.4.val)
+#[autodiff_forward(df1, Dual, Dual)]
+fn f1(x: &[f32; 2]) -> f32 {
+    x[0] + x[1]
+}
+
+// CHECK: ; abi_handling::f2
+// CHECK-NEXT: ; Function Attrs: {{.*}}noinline{{.*}}
+// debug-NEXT: define internal float @_ZN12abi_handling2f217h33732e9f83c91bc9E(ptr %f, float %x)
+// release-NEXT: define internal fastcc noundef float @_ZN12abi_handling2f217h33732e9f83c91bc9E(float noundef %x)
+#[autodiff_reverse(df2, Const, Active, Active)]
+fn f2(f: fn(f32) -> f32, x: f32) -> f32 {
+    f(x)
+}
+
+// CHECK: ; abi_handling::f3
+// CHECK-NEXT: ; Function Attrs: {{.*}}noinline{{.*}}
+// debug-NEXT: define internal float @_ZN12abi_handling2f317h9cd1fc602b0815a4E(ptr align 4 %x, ptr align 4 %y)
+// release-NEXT: define internal fastcc noundef float @_ZN12abi_handling2f317h9cd1fc602b0815a4E(float %x.0.val)
+#[autodiff_forward(df3, Dual, Dual, Dual)]
+fn f3<'a>(x: &'a f32, y: &'a f32) -> f32 {
+    *x * *y
+}
+
+// CHECK: ; abi_handling::f4
+// CHECK-NEXT: ; Function Attrs: {{.*}}noinline{{.*}}
+// debug-NEXT: define internal float @_ZN12abi_handling2f417h2f4a9a7492d91e9fE(float %x.0, float %x.1)
+// release-NEXT: define internal fastcc noundef float @_ZN12abi_handling2f417h2f4a9a7492d91e9fE(float noundef %x.0, float noundef %x.1)
+#[autodiff_forward(df4, Dual, Dual)]
+fn f4(x: (f32, f32)) -> f32 {
+    x.0 * x.1
+}
+
+// CHECK: ; abi_handling::f5
+// CHECK-NEXT: ; Function Attrs: {{.*}}noinline{{.*}}
+// debug-NEXT: define internal float @_ZN12abi_handling2f517hf8d4ac4d2c2a3976E(float %i.0, float %i.1)
+// release-NEXT: define internal fastcc noundef float @_ZN12abi_handling2f517hf8d4ac4d2c2a3976E(float noundef %i.0, float noundef %i.1)
+#[autodiff_forward(df5, Dual, Dual)]
+fn f5(i: Input) -> f32 {
+    i.x + i.y
+}
+
+// CHECK: ; abi_handling::f6
+// CHECK-NEXT: ; Function Attrs: {{.*}}noinline{{.*}}
+// debug-NEXT: define internal float @_ZN12abi_handling2f617h5784b207bbb2483eE(float %i.0, float %i.1)
+// release-NEXT: define internal fastcc noundef float @_ZN12abi_handling2f617h5784b207bbb2483eE(float noundef %i.0, float noundef %i.1)
+#[autodiff_forward(df6, Dual, Dual)]
+fn f6(i: NestedInput) -> f32 {
+    i.x + i.y.z * i.y.z
+}
+
+// df1
+// release: define internal fastcc { float, float } @fwddiffe_ZN12abi_handling2f117h536ac8081c1e4101E(float %x.0.val, float %x.4.val)
+// release-NEXT: start:
+// release-NEXT: %_0 = fadd float %x.0.val, %x.4.val
+// release-NEXT: %0 = insertvalue { float, float } undef, float %_0, 0
+// release-NEXT: %1 = insertvalue { float, float } %0, float 1.000000e+00, 1
+// release-NEXT: ret { float, float } %1
+// release-NEXT: }
+
+// debug: define internal { float, float } @fwddiffe_ZN12abi_handling2f117h536ac8081c1e4101E(ptr align 4 %x, ptr align 4 %"x'")
+// debug-NEXT: start:
+// debug-NEXT: %"'ipg" = getelementptr inbounds float, ptr %"x'", i64 0
+// debug-NEXT: %0 = getelementptr inbounds nuw float, ptr %x, i64 0
+// debug-NEXT: %"_2'ipl" = load float, ptr %"'ipg", align 4, !alias.scope !4, !noalias !7
+// debug-NEXT: %_2 = load float, ptr %0, align 4, !alias.scope !7, !noalias !4
+// debug-NEXT: %"'ipg2" = getelementptr inbounds float, ptr %"x'", i64 1
+// debug-NEXT: %1 = getelementptr inbounds nuw float, ptr %x, i64 1
+// debug-NEXT: %"_5'ipl" = load float, ptr %"'ipg2", align 4, !alias.scope !4, !noalias !7
+// debug-NEXT: %_5 = load float, ptr %1, align 4, !alias.scope !7, !noalias !4
+// debug-NEXT: %_0 = fadd float %_2, %_5
+// debug-NEXT: %2 = fadd fast float %"_2'ipl", %"_5'ipl"
+// debug-NEXT: %3 = insertvalue { float, float } undef, float %_0, 0
+// debug-NEXT: %4 = insertvalue { float, float } %3, float %2, 1
+// debug-NEXT: ret { float, float } %4
+// debug-NEXT: }
+
+// df2
+// release: define internal fastcc { float, float } @diffe_ZN12abi_handling2f217h33732e9f83c91bc9E(float noundef %x)
+// release-NEXT: invertstart:
+// release-NEXT: %_0.i = fmul float %x, %x
+// release-NEXT: %0 = insertvalue { float, float } undef, float %_0.i, 0
+// release-NEXT: %1 = insertvalue { float, float } %0, float 0.000000e+00, 1
+// release-NEXT: ret { float, float } %1
+// release-NEXT: }
+
+// debug: define internal { float, float } @diffe_ZN12abi_handling2f217h33732e9f83c91bc9E(ptr %f, float %x, float %differeturn)
+// debug-NEXT: start:
+// debug-NEXT: %"x'de" = alloca float, align 4
+// debug-NEXT: store float 0.000000e+00, ptr %"x'de", align 4
+// debug-NEXT: %toreturn = alloca float, align 4
+// debug-NEXT: %_0 = call float %f(float %x) #12
+// debug-NEXT: store float %_0, ptr %toreturn, align 4
+// debug-NEXT: br label %invertstart
+// debug-EMPTY:
+// debug-NEXT: invertstart:                                      ; preds = %start
+// debug-NEXT: %retreload = load float, ptr %toreturn, align 4
+// debug-NEXT: %0 = load float, ptr %"x'de", align 4
+// debug-NEXT: %1 = insertvalue { float, float } undef, float %retreload, 0
+// debug-NEXT: %2 = insertvalue { float, float } %1, float %0, 1
+// debug-NEXT: ret { float, float } %2
+// debug-NEXT: }
+
+// df3
+// release: define internal fastcc { float, float } @fwddiffe_ZN12abi_handling2f317h9cd1fc602b0815a4E(float %x.0.val)
+// release-NEXT: start:
+// release-NEXT: %0 = insertvalue { float, float } undef, float %x.0.val, 0
+// release-NEXT: %1 = insertvalue { float, float } %0, float 0x40099999A0000000, 1
+// release-NEXT: ret { float, float } %1
+// release-NEXT: }
+
+// debug: define internal { float, float } @fwddiffe_ZN12abi_handling2f317h9cd1fc602b0815a4E(ptr align 4 %x, ptr align 4 %"x'", ptr align 4 %y, ptr align 4 %"y'")
+// debug-NEXT: start:
+// debug-NEXT: %"_3'ipl" = load float, ptr %"x'", align 4, !alias.scope !9, !noalias !12
+// debug-NEXT: %_3 = load float, ptr %x, align 4, !alias.scope !12, !noalias !9
+// debug-NEXT: %"_4'ipl" = load float, ptr %"y'", align 4, !alias.scope !14, !noalias !17
+// debug-NEXT: %_4 = load float, ptr %y, align 4, !alias.scope !17, !noalias !14
+// debug-NEXT: %_0 = fmul float %_3, %_4
+// debug-NEXT: %0 = fmul fast float %"_3'ipl", %_4
+// debug-NEXT: %1 = fmul fast float %"_4'ipl", %_3
+// debug-NEXT: %2 = fadd fast float %0, %1
+// debug-NEXT: %3 = insertvalue { float, float } undef, float %_0, 0
+// debug-NEXT: %4 = insertvalue { float, float } %3, float %2, 1
+// debug-NEXT: ret { float, float } %4
+// debug-NEXT: }
+
+// df4
+// release: define internal fastcc { float, float } @fwddiffe_ZN12abi_handling2f417h2f4a9a7492d91e9fE(float noundef %x.0, float %"x.0'")
+// release-NEXT: start:
+// release-NEXT: %0 = insertvalue { float, float } undef, float %x.0, 0
+// release-NEXT: %1 = insertvalue { float, float } %0, float %"x.0'", 1
+// release-NEXT: ret { float, float } %1
+// release-NEXT: }
+
+// debug: define internal { float, float } @fwddiffe_ZN12abi_handling2f417h2f4a9a7492d91e9fE(float %x.0, float %"x.0'", float %x.1, float %"x.1'")
+// debug-NEXT: start:
+// debug-NEXT: %_0 = fmul float %x.0, %x.1
+// debug-NEXT: %0 = fmul fast float %"x.0'", %x.1
+// debug-NEXT: %1 = fmul fast float %"x.1'", %x.0
+// debug-NEXT: %2 = fadd fast float %0, %1
+// debug-NEXT: %3 = insertvalue { float, float } undef, float %_0, 0
+// debug-NEXT: %4 = insertvalue { float, float } %3, float %2, 1
+// debug-NEXT: ret { float, float } %4
+// debug-NEXT: }
+
+// df5
+// release: define internal fastcc { float, float } @fwddiffe_ZN12abi_handling2f517hf8d4ac4d2c2a3976E(float noundef %i.0, float %"i.0'")
+// release-NEXT: start:
+// release-NEXT: %_0 = fadd float %i.0, 1.000000e+00
+// release-NEXT: %0 = insertvalue { float, float } undef, float %_0, 0
+// release-NEXT: %1 = insertvalue { float, float } %0, float %"i.0'", 1
+// release-NEXT: ret { float, float } %1
+// release-NEXT: }
+
+// debug: define internal { float, float } @fwddiffe_ZN12abi_handling2f517hf8d4ac4d2c2a3976E(float %i.0, float %"i.0'", float %i.1, float %"i.1'")
+// debug-NEXT: start:
+// debug-NEXT: %_0 = fadd float %i.0, %i.1
+// debug-NEXT: %0 = fadd fast float %"i.0'", %"i.1'"
+// debug-NEXT: %1 = insertvalue { float, float } undef, float %_0, 0
+// debug-NEXT: %2 = insertvalue { float, float } %1, float %0, 1
+// debug-NEXT: ret { float, float } %2
+// debug-NEXT: }
+
+// df6
+// release: define internal fastcc { float, float } @fwddiffe_ZN12abi_handling2f617h5784b207bbb2483eE(float noundef %i.0, float %"i.0'", float noundef %i.1, float %"i.1'")
+// release-NEXT: start:
+// release-NEXT: %_3 = fmul float %i.1, %i.1
+// release-NEXT: %0 = fadd fast float %"i.1'", %"i.1'"
+// release-NEXT: %1 = fmul fast float %0, %i.1
+// release-NEXT: %_0 = fadd float %i.0, %_3
+// release-NEXT: %2 = fadd fast float %"i.0'", %1
+// release-NEXT: %3 = insertvalue { float, float } undef, float %_0, 0
+// release-NEXT: %4 = insertvalue { float, float } %3, float %2, 1
+// release-NEXT: ret { float, float } %4
+// release-NEXT: }
+
+// debug: define internal { float, float } @fwddiffe_ZN12abi_handling2f617h5784b207bbb2483eE(float %i.0, float %"i.0'", float %i.1, float %"i.1'")
+// debug-NEXT: start:
+// debug-NEXT: %_3 = fmul float %i.1, %i.1
+// debug-NEXT: %0 = fmul fast float %"i.1'", %i.1
+// debug-NEXT: %1 = fmul fast float %"i.1'", %i.1
+// debug-NEXT: %2 = fadd fast float %0, %1
+// debug-NEXT: %_0 = fadd float %i.0, %_3
+// debug-NEXT: %3 = fadd fast float %"i.0'", %2
+// debug-NEXT: %4 = insertvalue { float, float } undef, float %_0, 0
+// debug-NEXT: %5 = insertvalue { float, float } %4, float %3, 1
+// debug-NEXT: ret { float, float } %5
+// debug-NEXT: }
+
+fn main() {
+    let x = std::hint::black_box(2.0);
+    let y = std::hint::black_box(3.0);
+    let z = std::hint::black_box(4.0);
+    static Y: f32 = std::hint::black_box(3.2);
+
+    let in_f1 = [x, y];
+    dbg!(f1(&in_f1));
+    let res_f1 = df1(&in_f1, &[1.0, 0.0]);
+    dbg!(res_f1);
+
+    dbg!(f2(square, x));
+    let res_f2 = df2(square, x, 1.0);
+    dbg!(res_f2);
+
+    dbg!(f3(&x, &Y));
+    let res_f3 = df3(&x, &Y, &1.0, &0.0);
+    dbg!(res_f3);
+
+    let in_f4 = (x, y);
+    dbg!(f4(in_f4));
+    let res_f4 = df4(in_f4, (1.0, 0.0));
+    dbg!(res_f4);
+
+    let in_f5 = Input { x, y };
+    dbg!(f5(in_f5));
+    let res_f5 = df5(in_f5, Input { x: 1.0, y: 0.0 });
+    dbg!(res_f5);
+
+    let in_f6 = NestedInput { x, y: Wrapper { z: y } };
+    dbg!(f6(in_f6));
+    let res_f6 = df6(in_f6, NestedInput { x, y: Wrapper { z } });
+    dbg!(res_f6);
+}