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Re: Architecture / Instruction Set / Language co-design.

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EricP wrote:
> I think a better question would have been
> What specific architecture or instruction features on
> which machines benefit specific languages or OS requirements?
>
> E.g.
> Alpha LDQ_U Load Quadword Unaligned instruction masked the lower
> 3 address bits allowing them to be used for tagged pointers.

Wasn't that one of the required instructions to make it possible to 
handle string (byte) operations with 64-bit operations?

I.e. you would use LDQ_U on the (presumably arbitrarily aligned) char * 
passed in to strcpy() etc, along with another operation which would mask 
a register based on the lower three bits.

The key is of course that with such an instruction for the first word, 
all accesses would be aligned, making it safe to load 8 bytes, even if 7 
of them happened to be outside the end of the string. (It works because 
the using of protection is the memory page, which is also aligned.)

The fact that it would also work for languages that like to have tagged 
pointers might have been more of a happy coincidence?

Terje
-- 
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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Architecture / Instruction Set / Language co-design. Roberto Waltman <usenet@rwaltman.com> - 2011-07-14 15:37 -0400
  Re: Architecture / Instruction Set / Language co-design. blp@cs.stanford.edu (Ben Pfaff) - 2011-07-14 13:03 -0700
    Re: Architecture / Instruction Set / Language co-design. Peter Flass <Peter_Flass@Yahoo.com> - 2011-07-14 21:16 -0400
  Re: Architecture / Instruction Set / Language co-design. Peter Flass <Peter_Flass@Yahoo.com> - 2011-07-14 16:06 -0400
    Re: Architecture / Instruction Set / Language co-design. Charles Richmond <frizzle@tx.rr.com> - 2011-07-14 20:42 -0500
      Re: Architecture / Instruction Set / Language co-design. Peter Flass <Peter_Flass@Yahoo.com> - 2011-07-15 07:50 -0400
        Re: Architecture / Instruction Set / Language co-design. Anne & Lynn Wheeler <lynn@garlic.com> - 2011-07-15 09:56 -0400
        Re: Architecture / Instruction Set / Language co-design. John Levine <johnl@iecc.com> - 2011-07-15 17:38 +0000
          Re: Architecture / Instruction Set / Language co-design. Charles Richmond <frizzle@tx.rr.com> - 2011-07-15 23:22 -0500
            Re: Architecture / Instruction Set / Language co-design. John Levine <johnl@iecc.com> - 2011-07-17 19:33 +0000
  Re: Architecture / Instruction Set / Language co-design. cb@mer.df.lth.se (Christian Brunschen) - 2011-07-14 20:25 +0000
  Re: Architecture / Instruction Set / Language co-design. EricP <ThatWouldBeTelling@thevillage.com> - 2011-07-14 17:42 -0400
    Re: Architecture / Instruction Set / Language co-design. mac <acolvin@efunct.com> - 2011-07-17 15:31 +0000
      Re: Architecture / Instruction Set / Language co-design. Bill Findlay <yaldnif.w@blueyonder.co.uk> - 2011-07-17 16:59 +0100
      Re: Architecture / Instruction Set / Language co-design. Anne & Lynn Wheeler <lynn@garlic.com> - 2011-07-17 12:11 -0400
        Re: Architecture / Instruction Set / Language co-design. Mike Hore <mike_horeREM@OVE.invalid.aapt.net.au> - 2011-07-19 12:04 +1000
      Re: Architecture / Instruction Set / Language co-design. EricP <ThatWouldBeTelling@thevillage.com> - 2011-07-17 13:02 -0400
        Re: Architecture / Instruction Set / Language co-design. Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-07-17 20:42 +0200
          Re: Architecture / Instruction Set / Language co-design. anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-07-18 11:49 +0000
        Re: Architecture / Instruction Set / Language co-design. Andrew Reilly <areilly---@bigpond.net.au> - 2011-07-17 23:14 +0000
          Re: Architecture / Instruction Set / Language co-design. EricP <ThatWouldBeTelling@thevillage.com> - 2011-07-19 12:54 -0400
            Re: Architecture / Instruction Set / Language co-design. Andrew Reilly <areilly---@bigpond.net.au> - 2011-07-19 22:16 +0000
      Re: Architecture / Instruction Set / Language co-design. Roberto Waltman <usenet@rwaltman.com> - 2011-07-17 19:20 -0400
        Re: Architecture / Instruction Set / Language co-design. EricP <ThatWouldBeTelling@thevillage.com> - 2011-07-19 12:54 -0400
          Re: Architecture / Instruction Set / Language co-design. Roberto Waltman <usenet@rwaltman.com> - 2011-07-19 14:50 -0400
        Re: Architecture / Instruction Set / Language co-design. EricP <ThatWouldBeTelling@thevillage.com> - 2011-07-19 16:24 -0400
  Re: Architecture / Instruction Set / Language co-design. Andrew Reilly <areilly---@bigpond.net.au> - 2011-07-14 22:57 +0000
    Re: Architecture / Instruction Set / Language co-design. Michael S <already5chosen@yahoo.com> - 2011-07-19 16:16 -0700
  Re: Architecture / Instruction Set / Language co-design. EricP <ThatWouldBeTelling@thevillage.com> - 2011-07-14 19:04 -0400
  Re: Architecture / Instruction Set / Language co-design. Al Kossow <aek@bitsavers.org> - 2011-07-14 17:15 -0700
  Re: Architecture / Instruction Set / Language co-design. Robert Wessel <robertwessel2@yahoo.com> - 2011-07-14 20:34 -0500
  Re: Architecture / Instruction Set / Language co-design. torbenm@diku.dk (Torben Ægidius Mogensen) - 2011-07-15 10:28 +0200
  Re: Architecture / Instruction Set / Language co-design. kenney@cix.compulink.co.uk - 2011-07-15 04:31 -0500
  Re: Architecture / Instruction Set / Language co-design. Mark Thorson <nospam@sonic.net> - 2011-07-18 14:26 -0800
    Re: Architecture / Instruction Set / Language co-design. Charles Richmond <plano.net@aquaporin4.com> - 2011-07-20 01:10 -0500

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