Optimize pcrel access of globals

Optimize pcrel access of globals

This patch implements a RTL pass that looks for pc-relative loads of the
address of an external variable using the PCREL_GOT relocation and a
single load or store that uses that external address.

Produced by a cast of thousands:
 * Michael Meissner
 * Peter Bergner
 * Bill Schmidt
 * Alan Modra
 * Segher Boessenkool
 * Aaron Sawdey

gcc/ChangeLog:

	* config.gcc: Add rs6000-pcrel-opt.o.
	* config/rs6000/rs6000-pcrel-opt.c: New file.
	* config/rs6000/pcrel-opt.md: New file.
	* config/rs6000/predicates.md: Add d_form_memory predicate.
	* config/rs6000/rs6000-cpus.def: Add OPTION_MASK_PCREL_OPT.
	* config/rs6000/rs6000-passes.def: Add pass_pcrel_opt.
	* config/rs6000/rs6000-protos.h: Add reg_to_non_prefixed(),
	pcrel_opt_valid_mem_p(), output_pcrel_opt_reloc(),
	and make_pass_pcrel_opt().
	* config/rs6000/rs6000.c (reg_to_non_prefixed): Make global.
	(rs6000_option_override_internal): Add pcrel-opt.
	(rs6000_delegitimize_address): Support pcrel-opt.
	(rs6000_opt_masks): Add pcrel-opt.
	(pcrel_opt_valid_mem_p): New function.
	(reg_to_non_prefixed): Make global.
	(rs6000_asm_output_opcode): Reset prepend_p_to_next_insn.
	(output_pcrel_opt_reloc): New function.
	* config/rs6000/rs6000.md (loads_extern_addr): New attr.
	(pcrel_extern_addr): Set loads_extern_addr.
	Add include for pcrel-opt.md.
	* config/rs6000/rs6000.opt: Add -mpcrel-opt.
	* config/rs6000/t-rs6000: Add rules for pcrel-opt.c and
	pcrel-opt.md.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pcrel-opt-inc-di.c: New test.
	* gcc.target/powerpc/pcrel-opt-ld-df.c: New test.
	* gcc.target/powerpc/pcrel-opt-ld-di.c: New test.
	* gcc.target/powerpc/pcrel-opt-ld-hi.c: New test.
	* gcc.target/powerpc/pcrel-opt-ld-qi.c: New test.
	* gcc.target/powerpc/pcrel-opt-ld-sf.c: New test.
	* gcc.target/powerpc/pcrel-opt-ld-si.c: New test.
	* gcc.target/powerpc/pcrel-opt-ld-vector.c: New test.
	* gcc.target/powerpc/pcrel-opt-st-df.c: New test.
	* gcc.target/powerpc/pcrel-opt-st-di.c: New test.
	* gcc.target/powerpc/pcrel-opt-st-hi.c: New test.
	* gcc.target/powerpc/pcrel-opt-st-qi.c: New test.
	* gcc.target/powerpc/pcrel-opt-st-sf.c: New test.
	* gcc.target/powerpc/pcrel-opt-st-si.c: New test.
	* gcc.target/powerpc/pcrel-opt-st-vector.c: New test.