For a packed constrained array type with a Component_Size clause, it
may be possible to compute both its RM_Size and Esize. Do this as it
benefits GNATprove for checking validity of overlays.
Tested on x86_64-pc-linux-gnu, committed on trunk
gcc/ada/
* layout.adb (Layout_Type): Special case when RM_Size and Esize
can be computed for packed arrays.diff --git a/gcc/ada/layout.adb b/gcc/ada/layout.adb
--- a/gcc/ada/layout.adb
+++ b/gcc/ada/layout.adb
@@ -487,6 +487,48 @@ package body Layout is
then
Set_Alignment (E, Alignment (Component_Type (E)));
end if;
+
+ -- If packing was requested, the one-dimensional array is constrained
+ -- with static bounds, the component size was set explicitly, and
+ -- the alignment is known, we can set (if not set explicitly) the
+ -- RM_Size and the Esize of the array type, as RM_Size is equal to
+ -- (arr'length * arr'component_size) and Esize is the same value
+ -- rounded to the next multiple of arr'alignment. This is not
+ -- applicable to packed arrays that are implemented specially
+ -- in GNAT, i.e. when Packed_Array_Impl_Type is set.
+
+ if Is_Array_Type (E)
+ and then Number_Dimensions (E) = 1
+ and then not Present (Packed_Array_Impl_Type (E))
+ and then Has_Pragma_Pack (E)
+ and then Is_Constrained (E)
+ and then Compile_Time_Known_Bounds (E)
+ and then Known_Component_Size (E)
+ and then Known_Alignment (E)
+ then
+ declare
+ Abits : constant Int := UI_To_Int (Alignment (E)) * SSU;
+ Lo, Hi : Node_Id;
+ Siz : Uint;
+
+ begin
+ Get_Index_Bounds (First_Index (E), Lo, Hi);
+ Siz := (Expr_Value (Hi) - Expr_Value (Lo) + 1)
+ * Component_Size (E);
+
+ -- Do not overwrite a different value of 'Size specified
+ -- explicitly by the user. In that case, also do not set Esize.
+
+ if Unknown_RM_Size (E) or else RM_Size (E) = Siz then
+ Set_RM_Size (E, Siz);
+
+ if Unknown_Esize (E) then
+ Siz := ((Siz + (Abits - 1)) / Abits) * Abits;
+ Set_Esize (E, Siz);
+ end if;
+ end if;
+ end;
+ end if;
end if;
-- Even if the backend performs the layout, we still do a little in
