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Re: [patch] tree-ssa-dom.c: Use VEC(vrp_element_p,heap) instead ofVARRAY.


On Wed, 2005-04-27 at 13:12 -0400, Kazu Hirata wrote:
> Hi Diego,
> 
> > > Well, we can probably feed DOM similar information using
> > > SSA_NAME_VALUE_RANGE.
> > > 
> > If DOM doesn't use the VRP info for jump threading, then you
> > should be able to remove it.  Do make sure that tree-vrp.c is not
> > being silly on things caught by DOM, though.
> 
> In fact, most of my VRP patches (and some missed optmization in
> FRE/PRE) were inspired by instrumenting DOM and threadupdate to print
> out a message whenever all outgoing edges of a basic block are
> "threaded" to the same destination, which is just another way of
> saying "folding COND_EXPR_COND into a constant". :-)
Yea, that's a pretty good idea -- except for a small number of extreme
cases, if the threader threads all incoming edges to the same 
outgoing edge, then there's a good chance we can/should be looking
to catch that case in another optimizer such as VRP.

jeff



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