Patch for RTL expand bug affecting aarch64 vector code.

Patch for RTL expand bug affecting aarch64 vector code.

	gcc/
	PR middle-end/79794
    	* expmed.c (extract_bit_field_1): Add alt_rtl argument.  Before
	maybe_expand_insn call, set ops[0].target.  If still set after call,
	set alt_rtl.  Add extra arg to recursive calls.
	(extract_bit_field): Add alt_rtl argument.  Pass to
	extract_bit_field.
	* expmed.h (extract_bit_field): Fix prototype.
	* expr.c (emit_group_load_1, copy_blkmode_from_reg)
	(copy_blkmode_to_reg, read_complex_part, store_field): Pass extra NULL
	to extract_bit_field_calls.
	(expand_expr_real_1): Pass alt_rtl to expand_expr_real instead of 0.
	Pass alt_rtl to extract_bit_field calls.
	* calls.c (store_unaligned_arguments_into_psuedos)
	load_register_parameters): Pass extra NULL to extract_bit_field calls.
	* optabs.c (maybe_legitimize_operand): Clear op->target when call
	gen_reg_rtx.
	* optabs.h (struct expand_operand): Add target bitfield.

From-SVN: r248004