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Re: RAFTS beyond basic blocks; handling phi

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on 12/09/2013 23:53:05, "Alex McDonald" wrote:
> on 11/09/2013 13:10:16, "Alex McDonald" wrote:
>> on 11/09/2013 11:55:06, Anton wrote:
> 
>>>
>>> If there are loop back-edges involved, always choose to put the action
>>> on the back edge.
>>
>> OK. I presume there's a good reason for this; reduction in traffic?
>>
> 
> Yes, from what I can see; but that brings me to a problem with
> generating back edges. Consider
> 
>: foo begin + again ;
> 
> If we don't insert a phi on the back edge, but simply balance the
> stack;
> 
> B[1] <1> pop           ( a )
> B[1] <2> pop           ( a|c b )
> B[1] <3> + <1> <2>     ( c )
> B[1]     push <3>      ( -- )
> B[1]     jmp <1>
> 
> OK, but inefficent. Better is
> 
> B[1] <1> pop           ( a )
> B[1] <2> pop           ( a|c b )
> B[1] <4> +   <2> <3>   ( c )
> B[1] <3> phi <1> <4>   ( a|c )
> B[1]     jmp <2>
> 
> A few issues. Now I have a DCG rather than a DAG. That can be resolved
> by marking visits while walking what is now a DCG.
> 
> The other issue is determining that we need a B[1] jmp <2>; that is,
> not to the head of the block. Either that or the block is split
> between <1> and <2>; but again, how do we determine that? Can we use
> the left operand of <3> phi <1> <4> (the <1>, what would be the block
> entry) to select the split or branch point?

Clarification; that is, select <2> which follows <1>.

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RAFTS beyond basic blocks; handling phi "Alex McDonald" <blog@rivadpm.com> - 2013-09-10 16:46 +0100
  Re: RAFTS beyond basic blocks; handling phi awegel@arcor.de (Alex Wegel) - 2013-09-10 23:30 +0200
    Re: RAFTS beyond basic blocks; handling phi "Alex McDonald" <blog@rivadpm.com> - 2013-09-11 11:35 +0100
      Re: RAFTS beyond basic blocks; handling phi Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-09-11 05:50 -0500
        Re: RAFTS beyond basic blocks; handling phi "Alex McDonald" <blog@rivadpm.com> - 2013-09-11 12:07 +0100
          Re: RAFTS beyond basic blocks; handling phi "Alex McDonald" <blog@rivadpm.com> - 2013-09-11 12:50 +0100
            Re: RAFTS beyond basic blocks; handling phi anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-11 14:27 +0000
  Re: RAFTS beyond basic blocks; handling phi anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-11 10:55 +0000
    Re: RAFTS beyond basic blocks; handling phi "Alex McDonald" <blog@rivadpm.com> - 2013-09-11 13:10 +0100
      Re: RAFTS beyond basic blocks; handling phi Bernd Paysan <bernd.paysan@gmx.de> - 2013-09-11 20:33 +0200
        Re: RAFTS beyond basic blocks; handling phi "Alex McDonald" <blog@rivadpm.com> - 2013-09-11 19:53 +0100
          Re: RAFTS beyond basic blocks; handling phi Bernd Paysan <bernd.paysan@gmx.de> - 2013-09-11 21:57 +0200
            Re: RAFTS beyond basic blocks; handling phi anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-13 13:14 +0000
        Re: RAFTS beyond basic blocks; handling phi albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-09-12 10:39 +0000
      Re: RAFTS beyond basic blocks; handling phi "Alex McDonald" <blog@rivadpm.com> - 2013-09-12 23:53 +0100
        Re: RAFTS beyond basic blocks; handling phi "Alex McDonald" <blog@rivadpm.com> - 2013-09-12 23:55 +0100
          Re: RAFTS beyond basic blocks; handling phi "Alex McDonald" <blog@rivadpm.com> - 2013-09-13 10:16 +0100
        Re: RAFTS beyond basic blocks; handling phi anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-13 13:19 +0000
          Re: RAFTS beyond basic blocks; handling phi "Alex McDonald" <blog@rivadpm.com> - 2013-09-15 20:34 +0100
      Re: RAFTS beyond basic blocks; handling phi anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-09-13 11:38 +0000

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