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

[Zdenek Dvorak]

Hello,

> Ultimately, I dont see much difference other than implementation
> details...

... and about three times more memory spent, I would estimate. For a
single assignment statement, we have:

1) The var_decl node
2) The ssa name
3) modify_expr
4) operation_expr

+ pointers to link them together, versus

1) single entity containing just the operation code and two pointers to
   the arguments (+additional information like type, etc).

Zdenek