* tree-ssa-dce.c (cfg_altered): New global.
        (tree_dce_init): Initialize cfg_altered.
        (remove_dead_stmt): If we remove an edge in the CFG, then set
        CFG_ALTERED.
        (perform_tree_ssa_dce): If we altered the CFG, then invalidate
        the dominators.

        * gcc.c-torture/compile/pr21356.c: New test.

From-SVN: r101652