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

[Kazu Hirata]

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". :-)

Kazu Hirata