Re: Modern optimizing compilers

[Victor Porton <porton@narod.ru>]

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