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!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail
From: Victor Porton <porton@narod.ru>
Newsgroups: comp.lang.ada
Subject: Re: Modern optimizing compilers
Date: Tue, 22 Aug 2017 04:20:12 +0300
Organization: Aioe.org NNTP Server
Message-ID: <ong0si$1rt1$1@gioia.aioe.org>
References: <onfg07$140e$1@gioia.aioe.org>
 <30f25a94-fc6d-4663-9405-d4d8601d6681@googlegroups.com>
 <ong0d0$1rda$1@gioia.aioe.org> <ong0n2$1roi$1@gioia.aioe.org>
NNTP-Posting-Host: I58n5mqJebgcOFNDKXkBJw.user.gioia.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/4.14.10
X-Notice: Filtered by postfilter v. 0.8.2
Xref: news.eternal-september.org comp.lang.ada:47779
Date: 2017-08-22T04:20:12+03:00
List-Id: <comp.lang.ada>

Victor Porton wrote:

> Victor Porton wrote:
> 
>> gautier_niouzes@hotmail.com wrote:
>> 
>>> You can compile a package containing a test procedure putting 123 into
>>> an Integer field of a record (tagged or not) and look at the assembler
>>> output. With GNAT it's gcc -S -O2 test_pkg.adb NB: the procedure
>>> probably needs to feed then an "out" parameter to prevent the compiler
>>> optimizing out completely the assignment with 123.
>> 
>> It seems that your case is wrong.
>> 
>> This procedure has no other choice than to write into the referenced
>> record.
>> 
>> We can however check with code like:
>> 
>> procedure M is
>>   type T is record
>>     X: Integer;
>>   end record;
>> 
>>   I: T;
>> begin
>>   I.X := 10;
>>   Ada.Text_IO.Put_Line(Integer'Image(I.X));
>> end;
> 
> I don't understand the assembler output of compiling this program (with
> added "with Ada.Text_IO;") with GCC 7.1.0, but it looks like very poorly
> optimized (very long). I don't know why the assembler code is so long.

Oh, I forgot -O3 flag :-)

Not sure if the optimizer with -O3 is good, but now the code it much 
shorter, however yet seems for me too long.

>>> Gautier
>>> _____________________________________________________________
>>> A free online game in Ada: http://pasta.phyrama.com/game.html
>> 
-- 
Victor Porton - http://portonvictor.org