Add R_X86_64_[REX_]GOTPCRELX support to gas and ld

Add R_X86_64_[REX_]GOTPCRELX support to gas and ld

This patch adds support for the R_X86_64_GOTPCRELX and
R_X86_64_REX_GOTPCRELX relocations proposed in

https://groups.google.com/forum/#!topic/x86-64-abi/n9AWHogmVY0

to gas and ld.  It updates gas to generate R_X86_64_GOTPCRELX,
R_X86_64_REX_GOTPCRELX if there is a REX prefix, relocation for memory
operand, foo@GOTPCREL(%rip).  With the locally defined symbol, foo, we
convert

  mov foo@GOTPCREL(%rip), %reg

to

   lea foo(%rip), %reg

and convert

   call/jmp *foo@GOTPCREL(%rip)
to

   nop call foo/jmp foo nop

When PIC is false, convert

   test %reg, foo@GOTPCREL(%rip)
to

test $foo, %reg

and convert

   binop foo@GOTPCREL(%rip), %reg

to

   binop $foo, %reg

where binop is one of adc, add, and, cmp, or, sbb, sub, xor instructions.

bfd/

	* elf64-x86-64.c: Include opcode/i386.h.
	(x86_64_elf_howto_table): Add R_X86_64_GOTPCRELX and
	R_X86_64_REX_GOTPCRELX.
	(R_X86_64_standard): Replace R_X86_64_PLT32_BND with
	R_X86_64_REX_GOTPCRELX.
	(x86_64_reloc_map): Add BFD_RELOC_X86_64_GOTPCRELX and
	BFD_RELOC_X86_64_REX_GOTPCRELX.
	(need_convert_mov_to_lea): Renamed to ...
	(need_convert_load): This.
	(elf_x86_64_check_relocs): Handle R_X86_64_GOTPCRELX and
	R_X86_64_REX_GOTPCRELX.  Replace need_convert_mov_to_lea with
	need_convert_load.
	(elf_x86_64_gc_sweep_hook): Handle R_X86_64_GOTPCRELX and
	R_X86_64_REX_GOTPCRELX.
	(elf_x86_64_size_dynamic_sections): Likewise.
	(elf_x86_64_relocate_section): Likewise.
	(elf_x86_64_convert_mov_to_lea): Renamed to ...
	(elf_x86_64_convert_load): This.  Replace need_convert_mov_to_lea
	with need_convert_load.  Support R_X86_64_GOTPCRELX and
	R_X86_64_REX_GOTPCRELX transformations.
	* reloc.c (BFD_RELOC_X86_64_GOTPCRELX): New.
	(BFD_RELOC_X86_64_REX_GOTPCRELX): Likewise.
	* bfd-in2.h: Regenerated.
	* libbfd.h: Likewise.

gas/

	* config/tc-i386.c (tc_i386_fix_adjustable): Handle
	BFD_RELOC_X86_64_GOTPCRELX and BFD_RELOC_X86_64_REX_GOTPCRELX.
	(tc_gen_reloc): Likewise.
	(i386_validate_fix): Generate BFD_RELOC_X86_64_GOTPCRELX or
	BFD_RELOC_X86_64_REX_GOTPCRELX if fx_tcbit2 is set.
	* config/tc-i386.h (TC_FORCE_RELOCATION_LOCAL): Also return
	true for BFD_RELOC_X86_64_GOTPCRELX and
	BFD_RELOC_X86_64_REX_GOTPCRELX.

gas/testsuite/

	* gas/i386/i386.exp: Run x86-64-gotpcrel.
	* gas/i386/x86-64-gotpcrel.d: New file.
	* gas/i386/x86-64-gotpcrel.s: Likewise.
	* gas/i386/ilp32/x86-64-gotpcrel.d: Likewise.
	* gas/i386/x86-64-localpic.d: Replace R_X86_64_GOTPCREL with
	R_X86_64_REX_GOTPCRELX.
	* gas/i386/ilp32/x86-64-localpic.d: Likewise.

include/elf/

	* x86-64.h (R_X86_64_GOTPCRELX): New.
	(R_X86_64_REX_GOTPCRELX): Likewise.

ld/testsuite/

	* ld-ifunc/ifunc-5r-local-x86-64.d: Replace R_X86_64_GOTPCREL
	with R_X86_64_REX_GOTPCRELX.
	* ld-x86-64/plt-main1.rd: Likewise.
	* ld-x86-64/plt-main3.rd: Likewise.
	* ld-x86-64/plt-main4.rd: Likewise.
	* ld-x86-64/gotpcrel1.dd: New file.
	* ld-x86-64/gotpcrel1.out: Likewise.
	* ld-x86-64/gotpcrel1a.S: Likewise.
	* ld-x86-64/gotpcrel1b.c: Likewise.
	* ld-x86-64/gotpcrel1c.c: Likewise.
	* ld-x86-64/gotpcrel1d.S: Likewise.
	* ld-x86-64/load1.s: Likewise.
	* ld-x86-64/load1a.d: Likewise.
	* ld-x86-64/load1b.d: Likewise.
	* ld-x86-64/load1c.d: Likewise.
	* ld-x86-64/load1d.d: Likewise.
	* ld-x86-64/x86-64.exp: Run load1a, load1b, load1c and load1d
	tests.  Run gotpcrel1 test.