Hi Mike,

  The attached patch adds an aarch64 simulator to gdb's sim library.  It
  is based upon the smallaarch64sim project:

    http://sourceforge.net/projects/smallaarch64sim/

  I converted it to C (from C++) because I prefer coding in C, extended
  it so that it could run on non x86 hosts, and added some more
  instruction emulations.

  This is still a work in progress as it does not yet emulate all the
  aarch64 instructions, nor does it have a testsuite.  Plus of course
  there are bound to be bugs to be fixed.  But with this sim in place I
  am able to run the gcc and g++ testsuites for an aarch64-elf toolchain
  and see results like this:

		=== gcc Summary for aarch64-sim ===

    # of expected passes		89895
    # of unexpected failures	        3462
    # of expected failures		243
    # of unresolved testcases	        3
    # of unsupported tests		1903

		=== gcc Summary for aarch64-sim/-mabi=ilp32 ===

    # of expected passes		90026
    # of unexpected failures	        3276
    # of expected failures		242
    # of unresolved testcases	        4
    # of unsupported tests		1936

		=== g++ Summary for aarch64-sim ===

    # of expected passes		78136
    # of unexpected failures	        1318
    # of expected failures		261
    # of unsupported tests		3903

		=== g++ Summary for aarch64-sim/-mabi=ilp32 ===

    # of expected passes		78608
    # of unexpected failures	        960
    # of unexpected successes	        4
    # of expected failures		257
    # of unsupported tests		3895

  So an approximate 96% pass rate for gcc and a 98% pass rate for G++.
  Not too bad for a first attempt.

  Is this patch OK to apply ?

Cheers
  Nick

sim/ChangeLog
2015-06-28  Nick Clifton  <nickc@redhat.com>

	* configure.tgt (sim_arch): Add aarch64 target.
	* configure: Regenerate.
        * aarch64: New directory.
        * aarch64/aclocal.m4: Generate.
	* aarch64/config.in: Generate.
	* aarch64/configure: Generate.
	* aarch64/configure.ac: New file.
	* aarch64/cpustate.c: New file. Models the AArch64 registers.
	* aarch64/cpustate.h: New file.
	* aarch64/decode.h: Prototypes and types for the decoder
	functions. 
	* aarch64/gdb-if.c: New file. Interface with GDB.
	* aarch64/main.c: New file.  Stand alone front end for the
	simulator.
	* aarch64/Makefile.in: New file.
	* aarch64/memory.c: New file. Models the AArch64 memory subsystem.
	* aarch64/memory.h: New file.
	* aarch64/simulator.c: New file. Emulated AArch64 instructions.
	* aarch64/simulator.h: New file.

include/gdb/ChangeLog
2015-06-28  Nick Clifton  <nickc@redhat.com>

	* sim-aarch64.h: New file.