PR tree-optimization/58978
	* tree-vrp.c (all_imm_uses_in_stmt_or_feed_cond): Don't modify
	use_stmt by single_imm_use directly.  Only call single_imm_use
	on SSA_NAMEs.

	* gcc.c-torture/compile/pr58978.c: New test.

From-SVN: r204357