* simplify_rtx.c (simplify_subreg): Keep subregs on return values,
check CLASS_CANNOT_CHANGE_MODE before avoiding subreg on hard reg,
in case register wasn't OK previously, accept it now; allow
subregs of frame pointer if reload completed and frame pointer
is not needed.
* combine.c (sombine_simplify_rtx): Fix comment;
use subreg_lowpart_offset instead of subreg_lowpart_p
(gen_lowpart_for_combine): Use subreg_lowpart_offset.
* rtl.h (subreg_lowpart_parts_p): Kill.
(subreg_lowpart_offset, subreg_highpart_offset): Declare.
* simplify-rtx.c (simplify_subreg): Use subreg_lowpart_offset.
* emit-rtl.c (gen_lowpart_SUBREG): Use subreg_lowpart_offset;
(gen_lowpart_common): Likewise.
(subreg_lowpart_p): Likewise.
(subreg_lowpart_parts_p): Kill.
(subreg_lowpart_offset, subreg_highpart_offset): New function.
* emit-rtl.c (gen_lowpart_common): Use simplify_gen_subreg
to simplify SUBREG and REG.
(gen_highpart): Use simplify_gen_subreg for all simplifications.
* emit-rtl.c (gen_realpart, gen_imagpart): Do not handle
CONCAT specially.
* rtlanal.c (replace_regs): Use simplify_gen_subreg
From-SVN: r42850
