[Ada] Validity check failure with packed array and pragma

[Pierre-Marie de Rodat]

Fix a bug in which if validity checking is enabled, Initialize_Scalars
is enabled, optimization is turned on, and inlining is enabled, the
initialization of a packed array can cause Constraint_Error to be
incorrectly raised.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

2017-09-18  Bob Duff  <d...@adacore.com>

        * exp_ch3.adb (Build_Array_Init_Proc): If validity checking is enabled,
        and it's a bit-packed array, pass False to the Consider_IS parameter of
        Needs_Simple_Initialization.

gcc/testsuite/

2017-09-18  Bob Duff  <d...@adacore.com>

        * gnat.dg/validity_check.adb: New testcase.

Index: exp_ch3.adb
===================================================================
--- exp_ch3.adb (revision 252913)
+++ exp_ch3.adb (working copy)
@@ -517,6 +517,10 @@
 
    procedure Build_Array_Init_Proc (A_Type : Entity_Id; Nod : Node_Id) is
       Comp_Type        : constant Entity_Id  := Component_Type (A_Type);
+      Comp_Type_Simple : constant Boolean :=
+        Needs_Simple_Initialization
+          (Comp_Type, Consider_IS =>
+             not (Validity_Check_Copies and Is_Bit_Packed_Array (A_Type)));
       Body_Stmts       : List_Id;
       Has_Default_Init : Boolean;
       Index_List       : List_Id;
@@ -557,7 +561,7 @@
                   Convert_To (Comp_Type,
                     Default_Aspect_Component_Value (First_Subtype (A_Type)))));
 
-         elsif Needs_Simple_Initialization (Comp_Type) then
+         elsif Comp_Type_Simple then
             Set_Assignment_OK (Comp);
             return New_List (
               Make_Assignment_Statement (Loc,
@@ -589,7 +593,7 @@
          --  the dummy Init_Proc needed for Initialize_Scalars processing.
 
          if not Has_Non_Null_Base_Init_Proc (Comp_Type)
-           and then not Needs_Simple_Initialization (Comp_Type)
+           and then not Comp_Type_Simple
            and then not Has_Task (Comp_Type)
            and then not Has_Default_Aspect (A_Type)
          then
@@ -679,7 +683,7 @@
       --  init_proc.
 
       Has_Default_Init := Has_Non_Null_Base_Init_Proc (Comp_Type)
-                            or else Needs_Simple_Initialization (Comp_Type)
+                            or else Comp_Type_Simple
                             or else Has_Task (Comp_Type)
                             or else Has_Default_Aspect (A_Type);
 
Index: ../testsuite/gnat.dg/validity_check.adb
===================================================================
--- ../testsuite/gnat.dg/validity_check.adb     (revision 0)
+++ ../testsuite/gnat.dg/validity_check.adb     (revision 0)
@@ -0,0 +1,18 @@
+--  { dg-do run }
+--  { dg-options "-cargs -O -gnatn -gnatVa -gnatws -margs" }
+
+pragma Initialize_Scalars;
+
+procedure Validity_Check is
+
+   type Small_Int is mod 2**6;
+
+   type Arr is array (1 .. 16) of Small_Int;
+   pragma Pack (Arr);
+
+   S : Small_Int;
+   A : Arr;
+
+begin
+   null;
+end;