Re: CMOVE/CMOVE>

From	"Alex McDonald" <blog@rivadpm.com>
Newsgroups	comp.lang.forth
Subject	Re: CMOVE/CMOVE>
Date	2015-08-18 23:55 +0100
Organization	A noiseless patient Spider
Message-ID	<mr0d1a$ke7$1@dont-email.me> (permalink)
References	<62627f57-1e63-4156-844a-db5708923aaf@googlegroups.com> <2015Aug18.180551@mips.complang.tuwien.ac.at> <c3289222-a562-44db-a30a-1f8d58d0fc6b@googlegroups.com> <cc2c79a3-48ce-400e-b3b6-4474c9c47917@googlegroups.com> <70231de3-da52-405a-a20d-a578e9783f12@googlegroups.com>

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on 18/08/2015 18:41:19,  wrote:
> > On Tuesday, August 18, 2015 at 10:10:22 AM UTC-7, Michael Barry wrote:

>>
>> Isn't it true that the decision can be made based simply on whether sourc
> e start is less than destination start, regardless of count? Mine does
> tha t, but CMOVE> and CMOVE have equivalent performance, which might
> mot always be the case.
> 
> Yes, it is only necessary to compare the start addresses.

No, because if there's an overlap then there may be advantages in using
larger than CHAR sized moves. When there is an overlap, CMOVE> should
always do a character by character move (for instance, on the x86 REP
MOVS BYTE); otherwise much larger units can be CMOVE>d if there is no
overlap (REP MOVS DWORD or QWORD or MOVDQU thru XMM registers, etc). The
difference in performance can be considerable.

Thread

CMOVE/CMOVE> Mark Wills <markwills1970@gmail.com> - 2015-08-18 08:44 -0700
  Re: CMOVE/CMOVE> anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-18 16:05 +0000
    Re: CMOVE/CMOVE> november.nihal@gmail.com - 2015-08-18 09:34 -0700
      Re: CMOVE/CMOVE> anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-18 16:41 +0000
    Re: CMOVE/CMOVE> Mark Wills <markwills1970@gmail.com> - 2015-08-18 09:59 -0700
      Re: CMOVE/CMOVE> Michael Barry <barrym95838@yahoo.com> - 2015-08-18 10:10 -0700
        Re: CMOVE/CMOVE> hughaguilar96@gmail.com - 2015-08-18 10:41 -0700
          Re: CMOVE/CMOVE> "Alex McDonald" <blog@rivadpm.com> - 2015-08-18 23:55 +0100
            Re: CMOVE/CMOVE> anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-19 08:40 +0000
              Re: CMOVE/CMOVE> "Alex McDonald" <blog@rivadpm.com> - 2015-08-19 12:15 +0100
        Re: CMOVE/CMOVE> Mark Wills <markwills1970@gmail.com> - 2015-08-18 11:35 -0700
          Re: CMOVE/CMOVE> Mark Wills <markwills1970@gmail.com> - 2015-08-18 11:36 -0700
            Re: CMOVE/CMOVE> "HAA" <someone@microsoft.com> - 2015-08-20 04:39 +1000
          Re: CMOVE/CMOVE> "Elizabeth D. Rather" <erather@forth.com> - 2015-08-19 09:15 -1000
          Re: CMOVE/CMOVE> "HAA" <someone@microsoft.com> - 2015-08-28 22:39 +1000
            Re: CMOVE/CMOVE> Coos Haak <chforth@hccnet.nl> - 2015-08-28 15:06 +0200
              Re: CMOVE/CMOVE> "HAA" <someone@microsoft.com> - 2015-08-29 17:15 +1000
                Re: CMOVE/CMOVE> Coos Haak <chforth@hccnet.nl> - 2015-08-29 13:24 +0200
                Re: CMOVE/CMOVE> "HAA" <someone@microsoft.com> - 2015-08-31 11:38 +1000
                Re: CMOVE/CMOVE> "Elizabeth D. Rather" <erather@forth.com> - 2015-08-29 07:59 -1000
                Re: CMOVE/CMOVE> "HAA" <someone@microsoft.com> - 2015-08-30 13:00 +1000
            Re: CMOVE/CMOVE> Mark Wills <markwills1970@gmail.com> - 2015-08-28 07:33 -0700
            Re: CMOVE/CMOVE> Mark Wills <markwills1970@gmail.com> - 2015-08-28 07:36 -0700
              Re: CMOVE/CMOVE> "HAA" <someone@microsoft.com> - 2015-08-29 02:23 +1000
            Re: CMOVE/CMOVE> mhx@iae.nl - 2015-08-28 11:41 -0700
              Re: CMOVE/CMOVE> "HAA" <someone@microsoft.com> - 2015-08-29 17:30 +1000
        Re: CMOVE/CMOVE> anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-19 08:04 +0000
      Re: CMOVE/CMOVE> "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-08-19 02:48 -0400
        Re: CMOVE/CMOVE> Mark Wills <markwills1970@gmail.com> - 2015-08-19 00:49 -0700
    Re: CMOVE/CMOVE> Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-19 02:58 +0200

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