SSA operand interface change proposal

[Zdenek Dvorak]

Hello,

> As best I can tell, the 'ivuse' structure used thorughout
> tree-ssa-loop-ivopts.c contains a pointer to a tree which can be either
> a use, a def, or an expression of some sort.  If we proceed with an
> interface like this (which I think we ought to), this hunk of code will
> need to be reworked. I dont want to make this unbearably difficult
> however.  I guess the ivuse structure could have all three pointers
> (use_operand_p, def_operand_p, and tree *) , and a flag indicating which
> field it uses, but maybe there is a better solution.

in fact what *op_p refers to is determined by the enum use_type type
field.  So you can just make it an union and updating the code to
reflect this should be trivial.

Zdenek