Add enough compiler support to compile empty functions on x64.

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index 48c61022e008503fc3f5acddf15e398e02cb5ea2..96e665f4aa7ecff610f380f64d6fdcca8dfa61a6 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -14,6 +14,7 @@
 #include "vm/exceptions.h"
 #include "vm/flags.h"
 #include "vm/flow_graph_builder.h"
+#include "vm/flow_graph_compiler.h"
 #include "vm/longjump.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
@@ -129,6 +130,16 @@ static RawError* CompileFunctionHelper(const Function& function,
       if (setjmp(*bailout_jump.Set()) == 0) {
         FlowGraphBuilder graph_builder(parsed_function);
         graph_builder.BuildGraph();
+
+        // Try to compile on x64 (only for now).
+#ifdef TARGET_ARCH_X64
+        Assembler assembler;
+        FlowGraphCompiler graph_compiler(&assembler,
+                                         parsed_function,
+                                         graph_builder.blocks());
+        graph_compiler.CompileGraph();

[srdjan, 2012/02/24 23:13:02]

It would be better to implement "dummy" FlowGraphCompiler in _ia32 and simarm.
This can happen in a later CL (please add a TODO).

[Kevin Millikin (Google), 2012/02/27 08:22:07]

Agreed.  Done.

+#endif
+
       } else {
         // We bailed out.
         Error& bailout_error = Error::Handle(