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Re: PATCH: PR target/40470: unable to find a register to spill in class

Subject: Re: PATCH: PR target/40470: unable to find a register to spill in class ‘SSE_FIRST_REG’
From: "H.J. Lu"
Date: Wed, 17 Jun 2009 11:43:18 -0700
On Wed, Jun 17, 2009 at 11:34 AM, Jeff Law<law@xxxxxxxxxx> wrote:
> H.J. Lu wrote:
>>
>> On Wed, Jun 17, 2009 at 11:18 AM, Vladimir Makarov<vmakarov@xxxxxxxxxx>
>> wrote:
>>
>>>
>>> I am agree with Jeff and Richard.  There is one more reason to avoid
>>> using
>>> hard registers.  Usage of hard registers tends to create more spill
>>> failures
>>> in reload.
>>>
>>
>> It is not like you have a choice here. The register for those insns is
>> fixed.
>> Sooner or later you have to allocate xmm0 for them.
>>
>
> And how is that different from any other port that has insns which require
> specific registers for particular insns.  This is nothing new or uncommon.
>

Have you compared generated codes on such insns with and
without early hard register assignment? My observations are
early hard register assignment improves RA on insn with
fixed hard registers:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40480


-- 
H.J.

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