Add x86_64 code generation support

Utilizes r0..r7 in register allocator, implements spill/unsill
core regs as well as operations with stack pointer.

Change-Id: I973d5a1acb9aa735f6832df3d440185d9e896c67
Signed-off-by: Dmitry Petrochenko <dmitry.petrochenko@intel.com>
diff --git a/compiler/dex/quick/mir_to_lir.h b/compiler/dex/quick/mir_to_lir.h
index 77e5649..a4052cd 100644
--- a/compiler/dex/quick/mir_to_lir.h
+++ b/compiler/dex/quick/mir_to_lir.h
@@ -174,6 +174,8 @@
                           ArenaAllocator* const arena);
 Mir2Lir* X86CodeGenerator(CompilationUnit* const cu, MIRGraph* const mir_graph,
                           ArenaAllocator* const arena);
+Mir2Lir* X86_64CodeGenerator(CompilationUnit* const cu, MIRGraph* const mir_graph,
+                          ArenaAllocator* const arena);
 
 // Utility macros to traverse the LIR list.
 #define NEXT_LIR(lir) (lir->next)