Re: [tree-ssa] New regressions as of 2003-11-04

[law at redhat dot com]

In message <20031110195439.GA14860@atrey.karlin.mff.cuni.cz>, Zdenek Dvorak wri
tes:
 >It does not do any more or less work than the previous solution does; I
 >admit I did not measure it, but I would be really surprised if there was
 >any difference.  I will do the measurements, but it seems utterly stupid
 >waste of time to me.
I'm sorry if seems like a waste of time to you, but it's critically
important that we actually spend time looking at these issues.  Ignoring
them simply is not a viable option as it will ultimately lead to the
failure of tree-ssa.


 >>  >> You didn't do this kind of analysis with the COND_EXPR lowering code
 >>  >> for example, and if you had done so you probably would have noticed tha
 >t
 >>  >> were were missing many transformations that were working with the old
 >>  >> COND_EXPR code, but were not working with the new COND_EXPR code.
 >>  >
 >>  >Yes I did, and I stated it clearly when I posted the patch. And since
 >>  >they were mostly useless, I ignored it.
 >> Apparently you weren't looking that closely.  I have found numerous
 >> transformations we were missing because of the COND_EXPR lowering patch.
 >
 >I know about the one revealed by gcc.dg/tree-ssa/20030814-4.c and
 >gcc.dg/tree-ssa/20030814-5.c tests; this is IMHO the only reason why to
 >leave some form of post-tree-ssa cleanup.  Then there are some
 >superfluous goto removals, that should be done by cfg cleanup instead.
 >Anything else?
The COND_EXPR lowering code effectively disabled threading though
conditional jumps in the dominator optimizer.  I have already fixed
that, but it is something that I would have expected you to find if
you had thoroughly examined the COND_EXPR changes.




Jeff