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Re: [PATCH] Teach SCCVN/PRE about type-punning through unions



 Reverse Post Order (which is how hardcore computer scientist call
 topological order).

RPO produces a topological order, yes, but there are usually more topological orders for a graph than just that single one, while there is only one reverse postorder.

There are actually many reverse postorders unless you establish an order for nodes and/or edges:


A   B
| \ |
C   D

CDAB and DCAB, DBCA are all valid postorders (which makes BADC, BACD, ACBD three good RPO's). Needless to say, in GCC we do have such order for nodes to make compilation stable and so there is only one RPO as far as GCC is concerned.

Paolo


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