tree-optimization/118852 - wrong code with 502.gcc_r

tree-optimization/118852 - wrong code with 502.gcc_r

502.gcc_r when built with -fprofile-generate exposes a SLP discovery
issue where an IV forced live due to early break is not properly
discovered if its latch def is part of a different IVs SSA cycle.
To mitigate this we have to make sure to create an SLP instance
for the original IV.  Ideally we'd handle all vect_induction_def
the same but this is left for next stage1.

	PR tree-optimization/118852
	* tree-vect-slp.cc (vect_analyze_slp): For early-break
	forced-live IVs make sure we create an appropriate
	entry into the SLP graph.

	* gcc.dg/vect/pr118852.c: New testcase.