Re: [tree-ssa] cfg.texi needs reviewing by a native speaker (Was: Re: "Documentation by paper")

[law at redhat dot com]

In message <20040209223920.GP20341@kam.mff.cuni.cz>, Jan Hubicka writes:
 >> For example, the code to predict goto as not being executed simply doesn't
 >> exist in the tree-ssa code.  I'll also note that adding this predictor
 >> actually makes things significantly worse for perl.
 >
 >Isn't it because the GOTOs are inserted/removed randomly during
 >gimplification/optimization so this info simply don't make sense
 >anymore?  It works only when GOTOs writen by users are predicted by this
 >way.
No, the code doesn't exist at all.  

And if you insert it (carefully making sure that it only applies to user
written gotos) then it still loses badly.  I haven't investigated why.

 >> And it would seem to me that the looping predictors should be independent
 >> of the gimplification code.  Can you explain why they are not?
 >
 >They are using the continue hint
True, but we should be able to do something that is very similar (though 
not exact) using the loop discovery and analysis code.

 > and also know that copied loop headers
Well, the tree-ssa branch copies loop headers quite effectivel now.

However, we don't create preheaders, which is a problem unto itself, but
which as far as I can tell doesn't make a difference on the prediction
problems.



 >See analyze_brprob script in the  contrib directory.  It has some info
 >about use in it and you can see data collected by profiled tester at
 >http://www.suse.de/~aj/SPEC  (see result files and analyze_brprob
 >archive)
Thanks.  
jeff