Allow ADDR_EXPRs of TARGET_MEM_REFs

Allow ADDR_EXPRs of TARGET_MEM_REFs

This patch allows ADDR_EXPR <TARGET_MEM_REF ...>, which is useful
when calling internal functions that take pointers to memory that
is conditionally loaded or stored.  This is a prerequisite to the
following ivopts patch.

2018-01-13  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* expr.c (expand_expr_addr_expr_1): Handle ADDR_EXPRs of
	TARGET_MEM_REFs.
	* gimple-expr.h (is_gimple_addressable: Likewise.
	* gimple-expr.c (is_gimple_address): Likewise.
	* internal-fn.c (expand_call_mem_ref): New function.
	(expand_mask_load_optab_fn): Use it.
	(expand_mask_store_optab_fn): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r256627