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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.lang.forth
Subject: Re: Stack vs stackless operation
Date: Fri, 28 Feb 2025 21:55:05 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
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anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:
>anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:
>Another variant:
>
>: exchange ( addr1 addr2 -- )
>    dup @ rot !@ swap ! ;
>
>This uses the primitive
>
>'!@' ( u1 a-addr -- u2 ) gforth-experimental "store-fetch"
>   load U2 from A_ADDR, and store U1 there, as atomic operation
>
>I worry that the atomic part will result in it being slower than the
>versions that do not use !@.

It's barely noticable on Zen4, but it makes a big difference on the
Cortex-A55.  Therefore we decided to also have a nonatomic !@.  We renamed the atomic one into ATOMIC!@ and !@ is now the nonatomic version.

How do they perform?

On Zen4:
      !@          atomic!@
  821_538_216    880_459_702  cycles
3_815_202_629  3_710_937_849  instructions

On Cortex-A55:
   !@        atomic!@
3355427045  5856496676  cycles                                                      
3115589778  4318749543  instructions

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
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