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[Ada] Compute sizes when possible for packed array with Component_Size

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gcc/ada/

	* layout.adb (Layout_Type): Special case when RM_Size and Esize
	can be computed for packed arrays.
This commit is contained in:
Yannick Moy 2021-05-19 15:50:02 +02:00 committed by Pierre-Marie de Rodat
parent 5478d8a7ae
commit 36fcfed88c
1 changed files with 42 additions and 0 deletions
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42
gcc/ada/layout.adb
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@ -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