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* [gcc r12-2148] [Ada] Compute sizes when possible for packed array with Component_Size
@ 2021-07-08 13:36 Pierre-Marie de Rodat
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From: Pierre-Marie de Rodat @ 2021-07-08 13:36 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:36fcfed88c7cbb3d55a59cdd077e8b26107148b9
commit r12-2148-g36fcfed88c7cbb3d55a59cdd077e8b26107148b9
Author: Yannick Moy <moy@adacore.com>
Date: Wed May 19 15:50:02 2021 +0200
[Ada] Compute sizes when possible for packed array with Component_Size
gcc/ada/
* layout.adb (Layout_Type): Special case when RM_Size and Esize
can be computed for packed arrays.
Diff:
---
gcc/ada/layout.adb | 42 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 42 insertions(+)
diff --git a/gcc/ada/layout.adb b/gcc/ada/layout.adb
index 6dc4d7fb699..cbc296a6e45 100644
--- 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
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