Add enough compiler support to compile empty functions on x64.

runtime/vm/flow_graph_compiler_x64.h

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef VM_FLOW_GRAPH_COMPILER_X64_H_
+#define VM_FLOW_GRAPH_COMPILER_X64_H_
+
+#ifndef VM_FLOW_GRAPH_COMPILER_H_
+#error Include flow_graph_compiler.h instead of flow_graph_compiler_x64.h.
+#endif
+
+#include "vm/assembler.h"
+#include "vm/code_generator.h"
+#include "vm/intermediate_language.h"
+
+namespace dart {
+
+class ParsedFunction;
+
+class FlowGraphCompiler : public InstructionVisitor {
+ public:
+  explicit FlowGraphCompiler(Assembler* assembler,

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

remove explicit

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

Thanks, done.

+                             const ParsedFunction& parsed_function,
+                             const GrowableArray<BlockEntryInstr*>* blocks)
+      : assembler_(assembler),
+        parsed_function_(parsed_function),
+        blocks_(blocks),
+        pc_descriptors_list_(new CodeGenerator::DescriptorList()) { }
+
+  virtual ~FlowGraphCompiler() { }
+
+  void CompileGraph();
+
+ private:
+  // Bail out of the flow graph compiler.  Does not return to the caller.
+  void Bailout(const char* reason);
+
+  // Each visit function compiles a type of instruction.
+#define DECLARE_VISIT(type)                             \
+  virtual void Visit##type(type##Instr* instr);
+  FOR_EACH_INSTRUCTION(DECLARE_VISIT)
+#undef DECLARE_VISIT
+
+  // Compile a Value into register RAX.

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

Why into RAX and not on TOS?

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

This is 'pop', when we consume a value (for temps they should already be on top
of the stack).

I'll rename it LoadValue.  Eventually we'll want an explicit register argument,
I think, but I'll wait until that's obvious.

+  void CompileValue(Value* value);
+
+  // Infrastructure copied from class CodeGenerator.
+  void GenerateCallRuntime(intptr_t node_id,
+                           intptr_t token_index,
+                           const RuntimeEntry& entry);
+  void AddCurrentDescriptor(PcDescriptors::Kind kind,
+                            intptr_t node_id,
+                            intptr_t token_index);
+
+  Assembler* assembler_;
+  const ParsedFunction& parsed_function_;
+  const GrowableArray<BlockEntryInstr*>* blocks_;
+
+  CodeGenerator::DescriptorList* pc_descriptors_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(FlowGraphCompiler);
+};
+
+}  // namespace dart
+
+#endif  // VM_FLOW_GRAPH_COMPILER_X64_H_