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Re: [PATCH] Atom: Scheduler improvements for better imul placement


On Wed, Apr 11, 2012 at 6:10 PM, Richard Guenther
<richard.guenther@gmail.com> wrote:
> On Wed, Apr 11, 2012 at 3:38 PM, Andi Kleen <andi@firstfloor.org> wrote:
>> Igor Zamyatin <izamyatin@gmail.com> writes:
>>
>>> Hi All!
>>>
>>> It is known that imul placement is rather critical for Atom processors
>>> and changes try to improve imul scheduling for Atom.
>>>
>>> This gives +5% performance on several tests from new OA 2.0 testsuite
>>> from EEMBC.
>>>
>>> Tested for i386 and x86-64, ok for trunk?
>>
>> Did you measure how much this slows down the compiler when compiling
>> for Atom? The new pass looks rather slow.
>
> Also please explain why adjusting the automaton for Atom is not a way to
> attack this issue.

If I understand the question correctly - it's a dynamic check and it's
not clear how to describe this adjusting statically in machine
description

>
> Richard.
>
>> -Andi
>>
>> --
>> ak@linux.intel.com -- Speaking for myself only


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