PR 64878: do not jump thread across more than one back-edge

PR 64878: do not jump thread across more than one back-edge

2015-02-04  Sebastian Pop  <s.pop@samsung.com>
	    Brian Rzycki  <b.rzycki@samsung.com>

	PR tree-optimization/64878
	* tree-ssa-threadedge.c: Include tree-ssa-loop.h.
	(fsm_find_control_statement_thread_paths): Add parameter seen_loop_phi.
	Stop recursion at loop phi nodes after having visited a loop phi node.

	* testsuite/gcc.dg/tree-ssa/ssa-dom-thread-8.c: New.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@220491 138bc75d-0d04-0410-961f-82ee72b054a4