diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 69f07c4f663..71c480a24c6 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2020-04-23  Matthew Malcomson  <matthew.malcomson@arm.com>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR target/94383
+	* config/aarch64/aarch64.c (aapcs_vfp_sub_candidate): Account for C++17
+	empty base class artificial fields.
+	(aarch64_vfp_is_call_or_return_candidate): Warn when ABI PCS decision is
+	different after this fix.
+
 2020-04-23  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/94707
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index f728ac530a4..a81b0b2ac04 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -16442,9 +16442,19 @@ aarch64_member_type_forces_blk (const_tree field_or_array, machine_mode mode)
    If *MODEP is VOIDmode, then set it to the first valid floating point
    type.  If a non-floating point type is found, or if a floating point
    type that doesn't match a non-VOIDmode *MODEP is found, then return -1,
-   otherwise return the count in the sub-tree.  */
+   otherwise return the count in the sub-tree.
+
+   The AVOID_CXX17_EMPTY_BASE argument is to allow the caller to check whether
+   this function has changed its behavior after the fix for PR94384 -- this fix
+   is to avoid artificial fields in empty base classes.
+   When called with this argument as a NULL pointer this function does not
+   avoid the artificial fields -- this is useful to check whether the function
+   returns something different after the fix.
+   When called pointing at a value, this function avoids such artificial fields
+   and sets the value to TRUE when one of these fields has been set.  */
 static int
-aapcs_vfp_sub_candidate (const_tree type, machine_mode *modep)
+aapcs_vfp_sub_candidate (const_tree type, machine_mode *modep,
+			 bool *avoid_cxx17_empty_base)
 {
   machine_mode mode;
   HOST_WIDE_INT size;
@@ -16520,7 +16530,8 @@ aapcs_vfp_sub_candidate (const_tree type, machine_mode *modep)
 	    || TREE_CODE (TYPE_SIZE (type)) != INTEGER_CST)
 	  return -1;
 
-	count = aapcs_vfp_sub_candidate (TREE_TYPE (type), modep);
+	count = aapcs_vfp_sub_candidate (TREE_TYPE (type), modep,
+					 avoid_cxx17_empty_base);
 	if (count == -1
 	    || !index
 	    || !TYPE_MAX_VALUE (index)
@@ -16558,7 +16569,18 @@ aapcs_vfp_sub_candidate (const_tree type, machine_mode *modep)
 	    if (TREE_CODE (field) != FIELD_DECL)
 	      continue;
 
-	    sub_count = aapcs_vfp_sub_candidate (TREE_TYPE (field), modep);
+	    /* Ignore C++17 empty base fields, while their type indicates
+	       they do contain padding, they have zero size and thus don't
+	       contain any padding.  */
+	    if (cxx17_empty_base_field_p (field)
+		&& avoid_cxx17_empty_base)
+	      {
+		*avoid_cxx17_empty_base = true;
+		continue;
+	      }
+
+	    sub_count = aapcs_vfp_sub_candidate (TREE_TYPE (field), modep,
+						 avoid_cxx17_empty_base);
 	    if (sub_count < 0)
 	      return -1;
 	    count += sub_count;
@@ -16591,7 +16613,8 @@ aapcs_vfp_sub_candidate (const_tree type, machine_mode *modep)
 	    if (TREE_CODE (field) != FIELD_DECL)
 	      continue;
 
-	    sub_count = aapcs_vfp_sub_candidate (TREE_TYPE (field), modep);
+	    sub_count = aapcs_vfp_sub_candidate (TREE_TYPE (field), modep,
+						 avoid_cxx17_empty_base);
 	    if (sub_count < 0)
 	      return -1;
 	    count = count > sub_count ? count : sub_count;
@@ -16718,10 +16741,26 @@ aarch64_vfp_is_call_or_return_candidate (machine_mode mode,
     }
   else if (type && composite_p)
     {
-      int ag_count = aapcs_vfp_sub_candidate (type, &new_mode);
-
+      bool avoided = false;
+      int ag_count = aapcs_vfp_sub_candidate (type, &new_mode, &avoided);
       if (ag_count > 0 && ag_count <= HA_MAX_NUM_FLDS)
 	{
+	  static unsigned last_reported_type_uid;
+	  unsigned uid = TYPE_UID (TYPE_MAIN_VARIANT (type));
+	  int alt;
+	  if (warn_psabi
+	      && avoided
+	      && uid != last_reported_type_uid
+	      && ((alt = aapcs_vfp_sub_candidate (type, &new_mode, NULL))
+		  != ag_count))
+	    {
+	      gcc_assert (alt == -1);
+	      last_reported_type_uid = uid;
+	      inform (input_location, "parameter passing for argument of type "
+		      "%qT when C++17 is enabled changed to match C++14 "
+		      "in GCC 10.1", type);
+	    }
+
 	  if (is_ha != NULL) *is_ha = true;
 	  *count = ag_count;
 	}