From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!news.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail
From: Victor Porton <porton@narod.ru>
Newsgroups: comp.lang.ada
Subject: Re: GNAT 4.9 - missing optimization feature?
Date: Wed, 06 Aug 2014 17:19:08 +0300
Organization: Aioe.org NNTP Server
Message-ID: <lrtdgp$93q$1@speranza.aioe.org>
References: <lrrnc5$kmk$1@speranza.aioe.org>
NNTP-Posting-Host: AnnUDmZwVERVUXyHDyOl5A.user.speranza.aioe.org
Mime-Version: 1.0
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 7Bit
X-Complaints-To: abuse@aioe.org
User-Agent: KNode/4.12.4
X-Notice: Filtered by postfilter v. 0.8.2
Xref: news.eternal-september.org comp.lang.ada:21484
Date: 2014-08-06T17:19:08+03:00
List-Id: <comp.lang.ada>

Victor Porton wrote:

> The below program, compiled with GNAT 4.9, calls Adjust two times when
> copying a T1 object.
> 
> But it does the same operations with a T2 object without calling Adjust.
> 
> So calling Adjust on a T1 object is here redundant and can be optimized
> away for greater performance. If I recall correctly, Ada Reference Manual
> allows this kind of optimization.
> 
> So GNAT is not as good as I expected, isn't it?
> 
> with Ada.Finalization;
> with Ada.Text_IO;
> 
> procedure Main is
> 
>    type T1 is new Ada.Finalization.Controlled with null record;
>    type T2 is new Ada.Finalization.Limited_Controlled with null record;
>    
>    overriding procedure Adjust(Object: in out T1) is
>    begin
>       Ada.Text_IO.Put_Line("Adjust");
>    end;
> 
>    function F return T1 is
>    begin
>       return (Ada.Finalization.Controlled with null record);
>    end;
>    
>    function F return T2 is
>    begin
>       return (Ada.Finalization.Limited_Controlled with null record);
>    end;
>    
>    X: T1 := F;
>    Y: T2 := F;
> 
> begin
>    null;
> end;

Is it true that this kind of optimization is legitimate accordingly ARM?

-- 
Victor Porton - http://portonvictor.org