[Ada] Tweak the sloc of Compile_Time_Warning warnings

2019-08-14  Bob Duff  <duff@adacore.com>

gcc/ada/

	* sem_prag.adb (Validate_Compile_Time_Warning_Error): Attach the
	warning to the Sloc of the first pragma argument, rather than to
	the pragma itself. This is to make pragmas processed after the
	back end use the same Sloc as pragmas processed earlier, in the
	front end. There's no reason for this discrepancy, and it
	hinders further work on this ticket.

From-SVN: r274461

gcc/ada/ChangeLog

 2019-08-14  Bob Duff  <duff@adacore.com>
 
+	* sem_prag.adb (Validate_Compile_Time_Warning_Error): Attach the
+	warning to the Sloc of the first pragma argument, rather than to
+	the pragma itself. This is to make pragmas processed after the
+	back end use the same Sloc as pragmas processed earlier, in the
+	front end. There's no reason for this discrepancy, and it
+	hinders further work on this ticket.
+
+2019-08-14  Bob Duff  <duff@adacore.com>
+
 	* sem.ads (Inside_A_Generic): Remove the ??? comment.
 
 2019-08-14  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/sem_prag.adb

@@ -336,8 +336,8 @@ package body Sem_Prag is
    --  and alignment values performed by the back end.
 
    --  Note: the reason we store a Source_Ptr value instead of a Node_Id is
-   --  that by the time Validate_Unchecked_Conversions is called, Sprint will
-   --  already have modified all Sloc values if the -gnatD option is set.
+   --  that by the time Validate_Compile_Time_Warning_Errors is called, Sprint
+   --  will already have modified all Sloc values if the -gnatD option is set.
 
    type CTWE_Entry is record
       Eloc  : Source_Ptr;
@@ -32147,9 +32147,10 @@ package body Sem_Prag is
    -----------------------------------------
 
    procedure Validate_Compile_Time_Warning_Error (N : Node_Id) is
+      Arg1  : constant Node_Id := First (Pragma_Argument_Associations (N));
    begin
       Compile_Time_Warnings_Errors.Append
-        (New_Val => CTWE_Entry'(Eloc  => Sloc (N),
+        (New_Val => CTWE_Entry'(Eloc  => Sloc (Arg1),
                                 Scope => Current_Scope,
                                 Prag  => N));
    end Validate_Compile_Time_Warning_Error;