re PR rtl-optimization/46034 (internal compiler error: segmentation fault)

	PR rtl-optimization/46034
	PR rtl-optimization/46212
	PR rtl-optimization/46248
	* combine.c (try_combine): If added_sets_2 where i0dest_in_i0src
	and i0 feeds i1 and i1 feeds i2 or i0 feeds i2, make a copy of i1src
	before i0dest -> i0src substitution and pass 1 instead of 0 as last
	argument to subst on i2pat.

	* gcc.c-torture/compile/pr46034.c: New test.
	* gcc.c-torture/compile/pr46248.c: New test.
	* gcc.dg/pr46212.c: New test.

From-SVN: r166231