re PR tree-optimization/34244 (VRP/SCEV miscompiles Firefox)

re PR tree-optimization/34244 (VRP/SCEV miscompiles Firefox)

	PR tree-optimization/34244
	* tree-vrp.c (adjust_range_with_scev): Clear scev cache.
	(record_numbers_of_iterations): New function.
	(execute_vrp): Cache the numbers of iterations of loops.
	* tree-scalar-evolution.c (scev_reset_except_niters):
	New function.
	(scev_reset): Use scev_reset_except_niters.
	* tree-scalar-evolution.h (scev_reset_except_niters): Declare.

	* gcc.dg/tree-ssa/pr34244.c: New test.

From-SVN: r130527