Make more use of byte_lowpart_offset

[Jeff Law]

On 08/23/2017 04:53 AM, Richard Sandiford wrote:
> This patch uses byte_lowpart_offset in places that open-coded the
> calculation.
> 
> Tested on aarch64-linux-gnu and x86_64-linux-gnu, and by making sure
> that there were no differences in testsuite assembly output for one
> target per CPU.  OK to install?
> 
> Richard
> 
> 
> 2017-08-23  Richard Sandiford  <richard.sandiford@linaro.org>
> 	    Alan Hayward  <alan.hayward@arm.com>
> 	    David Sherwood  <david.sherwood@arm.com>
> 
> gcc/
> 	* caller-save.c (replace_reg_with_saved_mem): Use byte_lowpart_offset.
> 	* combine.c (gen_lowpart_for_combine): Likewise.
> 	* dwarf2out.c (rtl_for_decl_location): Likewise.
> 	* final.c (alter_subreg): Likewise.
> 	* rtlhooks.c (gen_lowpart_general): Likewise.
> 	(gen_lowpart_if_possible): Likewise.
OK.
jeff