Move to a BackendRepr based sol

Author: Sa4dUs

compiler/rustc_monomorphize/src/partitioning/autodiff.rs

@@ -1,4 +1,3 @@
-use rustc_abi::HasDataLayout;
 use rustc_ast::expand::autodiff_attrs::{AutoDiffItem, DiffActivity};
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::bug;
@@ -17,7 +16,6 @@ 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![];
@@ -82,18 +80,12 @@ fn adjust_activity_to_abi<'tcx>(tcx: TyCtxt<'tcx>, fn_ty: Ty<'tcx>, da: &mut Vec
             }
         };
 
-        let is_product = |t: Ty<'tcx>| matches!(t.kind(), ty::Tuple(_) | ty::Adt(_, _));
-
-        // NOTE: When an ADT (Algebraic Data Type) has fewer than two fields and a total size less than pointer_size * 2,
-        // LLVM will pass its fields separately instead of as a single aggregate.
-        if layout.size() <= pointer_size * 2 && is_product(*ty) {
-            let n_scalars = count_leaf_fields(tcx, *ty);
-            if n_scalars <= 2 {
-                for _ in 0..n_scalars.saturating_sub(1) {
-                    new_activities.push(da[i].clone());
-                    new_positions.push(i + 1);
-                }
+        match layout.backend_repr() {
+            rustc_abi::BackendRepr::ScalarPair(_, _) => {
+                new_activities.push(da[i].clone());
+                new_positions.push(i + 1);
             }
+            _ => {}
         }
     }
     // now add the extra activities coming from slices
@@ -105,29 +97,6 @@ fn adjust_activity_to_abi<'tcx>(tcx: TyCtxt<'tcx>, fn_ty: Ty<'tcx>, da: &mut Vec
     }
 }
 
-fn count_leaf_fields<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> usize {
-    match ty.kind() {
-        ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::FnPtr(_, _) => 1,
-        ty::RawPtr(ty, _) => count_leaf_fields(tcx, *ty),
-        ty::Ref(_, ty, _) => count_leaf_fields(tcx, *ty),
-        ty::Array(ty, len) => {
-            if let Some(len) = len.try_to_target_usize(tcx) {
-                count_leaf_fields(tcx, *ty) * len as usize
-            } else {
-                1 // Not sure about how to handle this case
-            }
-        }
-        ty::Adt(def, substs) if def.is_struct() => def
-            .non_enum_variant()
-            .fields
-            .iter()
-            .map(|f| count_leaf_fields(tcx, f.ty(tcx, substs)))
-            .sum(),
-        ty::Tuple(substs) => substs.iter().map(|t| count_leaf_fields(tcx, t)).sum(),
-        _ => 0,
-    }
-}
-
 pub(crate) fn find_autodiff_source_functions<'tcx>(
     tcx: TyCtxt<'tcx>,
     usage_map: &UsageMap<'tcx>,