Possibly a bug

[Eric Botcazou]

> hello.c: In function ‘main’:
> hello.c:13:1: internal compiler error: in calc_dfs_tree, at dominance.c:394
> Please submit a full bug report,
> with preprocessed source if appropriate.
> See <http://gcc.gnu.org/bugs.html> for instructions.

This error means that some basic blocks are unreachable in the CFG.  The CFG 
needs to be cleaned up before that point.

-- 
Eric Botcazou