[Patch,avr]: Ad PR rtl-optimization/52543: Undo the MEM->UNSPEC hack

[Georg-Johann Lay]

PR52543 required to represent a load from non-generic address spaces as UNSPEC
instead of as MEM to avoid a gross code bloat.

http://gcc.gnu.org/PR52543

lower-subreg's cost model is still broken: It assumes that any loads from MEM
are from the generic address space and does not care for address spaces in its
cost model.

This patch undoes the changes from SVN r185605

http://gcc.gnu.org/viewcvs?view=revision&revision=185605

and installs a different but less intrusive hack around PR52543:

targetm.mode_dependent_address_p has an address space parameter so that the
backend can pretend all non-generic addresses are mode-dependent.

This keeps lower-subreg.c from splitting the loads, and it is possible to
represent the loads as MEM and there is no more the need to represent them as
UNSPECs.

This patch is still not an optimal solution but the code is much closer to a
clean solution now.

Ok for trunk?

Johann


	PR rtl-optimization/52543
	* config/avr/avr.c (avr_mode_dependent_address_p): Return true for
	all non-generic address spaces.
	(TARGET_SECONDARY_RELOAD): New hook define to...
	(avr_secondary_reload): ...this new static function.
	* config/avr/avr.md (reload_in<mode>): New insns.

	Undo r185605 (mostly):
	* config/avr/avr-protos.h (avr_load_lpm): Remove.
	* config/avr/avr.c (avr_load_libgcc_p): Don't restrict to __flash loads.
	(avr_out_lpm): Also handle loads > 1 byte.
	(avr_load_lpm): Remove.
	(avr_find_unused_d_reg): New static function.
	(avr_out_lpm_no_lpmx): New static function.
	(adjust_insn_length): Remove ADJUST_LEN_LOAD_LPM.
	* config/avr/avr.md (unspec): Remove UNSPEC_LPM.
	(load_<mode>_libgcc): Use MEM instead of UNSPEC_LPM.
	(load_<mode>, load_<mode>_clobber): Remove.
	(mov<mode>): For multi-byte move from non-generic
	16-bit address spaces: Expand to *mov<mode> again.
	(load<mode>_libgcc): New expander.
	(split-lpmx): Remove split.

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