Re: [patch] Performance patch for MIPS conditional move in expr.c

[Andrew Pinski <andrew dot pinski at caviumnetworks dot com>]

On Wed, Nov 14, 2012 at 1:45 PM, Steve Ellcey <sellcey@mips.com> wrote:
> On Wed, 2012-11-14 at 12:00 -0800, Andrew Pinski wrote:
>
>> I know exactly where this code comes from; I have looked at the
>> benchmark as one of the reason why I add expand_cond_expr_using_cmove
>> in the first place.  Anyways you should look into removing
>> TARGET_PROMOTE_PROTOTYPES because I found that also fixes the problem
>> mentioned here.
>>
>> Thanks,
>> Andrew Pinski
>
> Removing TARGET_PROMOTE_PROTOTYPES looks interesting but I don't know if
> it is possible for compatibility reasons.  I am still looking at my
> example though, I see GCC doing:
>
> andi    $5,$5,0x1
> xori    $5,$5,0x1
> movz    $2,$4,$5
>
> When it should just do:
>
> andi    $5,$5,0x1
> movn    $2,$4,$5

Yes I have a few patches for improving this case.  I have not
submitted them yet though.
Attached is the assembly I get from a 4.7 toolchain with all of the
changes I have internally applied; this is for n32 (though o32
produces the exact same code in this case).  I will try to post some
more in the next coming weeks.

Thanks,
Andrew Pinski


>
>
> Steve Ellcey
> sellcey@mips.com
>
>

Attachment: n32.s
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