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Subject: Re: g++ 3.4 and -fprofile-generate

Author: Robert Hyatt

Date: 12:26:50 02/16/05

Go up one level in this thread


On February 16, 2005 at 15:15:53, Frank Phillips wrote:

>On February 16, 2005 at 13:19:46, Robert Hyatt wrote:
>
>>On February 16, 2005 at 13:09:14, Frank Phillips wrote:
>>
>>>Has anybody got any experience with g++ 3.4 for amd64 (x86_64) - for Linux?
>>>
>>>I have been using the profile generated optimisation option, but the code it
>>>produces is no faster then with simple -O3.
>>>
>>>I simply compile with -fprofile-generate
>>>then run,
>>>then recompile with -fprofile-use.
>>>
>>>The relevant *.gcno, *.gcda files are produced.  Must be doing something
>>>wrong.....
>>>
>>>Frank
>>
>>
>>It has never worked well for me.  In fact, it usually crashes when I try to do
>>this for crafty.  ICC (Intel's compiler) works fine and that is what I use
>>myself.
>>
>
>Oh... the last version of ICC I used produced fast 32 bit code.  Does it now do
>amd 64 bit ?
>
>Frank
>

No.  Sorry.  I completely overlooked the AMD-64 in your text as that has become
so common to see over the past year.  ICC is 32 bits only although it will be 64
bit before long...


>
>>You need a good test set of data so that it can accurately predict each branch
>>and move code to optimize branch prediction at run-time...  The positions you
>>test need to pretty accurately represent what happens in a real game.



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