[tree-ssa] Maintaining/representing def-use/use-def information

[Zdenek Dvorak]

Hello,

> No, we don't.  We don't have any concept of "defining variable" or
> "versions" at all.  Though all SSA construction papers talk about building
> versions of source variables, once you start doing transformations, that
> idea becomes quickly meaningless.

except for ssa-pre, that requires the original variable names.  I still
consider it an indication that there is something rotten with the
optimization, but did not get the idea how to make it better so far.

Zdenek