Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.forth > #25656

Re: RAFTS beyond basic blocks; handling phi

From anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups comp.lang.forth
Subject Re: RAFTS beyond basic blocks; handling phi
Date 2013-09-13 13:19 +0000
Organization Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID <2013Sep13.151922@mips.complang.tuwien.ac.at> (permalink)
References <l0neru$oj5$1@dont-email.me> <2013Sep11.125505@mips.complang.tuwien.ac.at> <l0pmjc$8ot$1@dont-email.me> <l0tgkl$7k2$1@dont-email.me>

Show all headers | View raw

"Alex McDonald" <blog@rivadpm.com> writes:
>: foo begin + again ;
...
>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>

Yes, since there is a jmp to <2>, a new BB starts there.  Also, phi
instructions are at the start of the BB.  I.e., it should look as
follows:

>B[1] <1> pop           ( a )
>B[2] <3> phi <1> <4>   ( a|c )  
>B[2] <2> pop           ( a|c b )
>B[2] <4> +   <2> <3>   ( c )
>B[2]     jmp <3>

After phi removal, this is:

>B[1] <1> pop           ( a )
>B[1] <3> mov <1>
>B[2] <2> pop           ( a|c b )
>B[2] <4> +   <2> <3>   ( c )
>B[2] <3> mov <4>
>B[2]     jmp <2>

>A few issues. Now I have a DCG rather than a DAG.

Yes, if you look at the data flow graph including phi nodes and their
edges, you can get cycles.

>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?

Every branch target starts a new basic block.  Or maybe I
misunderstand your problem.

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
     New standard: http://www.forth200x.org/forth200x.html
   EuroForth 2013: http://www.euroforth.org/ef13/

Back to comp.lang.forth | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

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

csiph-web