re PR tree-optimization/56448 (cc1 hangs on volatile array with -O or above)

re PR tree-optimization/56448 (cc1 hangs on volatile array with -O or above)

	PR tree-optimization/56448
	* fold-const.c (operand_equal_p) <case tcc_reference>: Don't look at
	TREE_SIDE_EFFECTS if flags contain OEP_CONSTANT_ADDRESS_OF.
	Clear OEP_CONSTANT_ADDRESS_OF from flags before recursing on second or
	later operands of the references, or even first operand for
	INDIRECT_REF, TARGET_MEM_REF or MEM_REF.

	* gcc.c-torture/compile/pr56448.c: New test.

From-SVN: r196278