Last snapshot bits to get working precompiled hello_world on x64.

runtime/vm/snapshot.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_SNAPSHOT_H_
 #define VM_SNAPSHOT_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
@@ skipping 178 matching lines @@
   // The following fields are potentially unaligned.
   int64_t unaligned_length_;  // Stream length.
   int64_t unaligned_kind_;  // Kind of snapshot.
 
   // Variable length data follows here.
 
   DISALLOW_COPY_AND_ASSIGN(Snapshot);
 };
 
 
+class InstructionsSnapshot : ValueObject {
+ public:
+  explicit InstructionsSnapshot(const void* raw_memory)
+    : raw_memory_(raw_memory) {
+    ASSERT(Utils::IsAligned(raw_memory, OS::kMaxPreferredCodeAlignment));
+  }
+
+  void* instructions_start() {
+    return reinterpret_cast<void*>(
+        reinterpret_cast<uword>(raw_memory_) + kHeaderSize);
+  }
+
+  uword instructions_size() {
+    uword snapshot_size = *reinterpret_cast<const uword*>(raw_memory_);
+    return snapshot_size - kHeaderSize;
+  }
+
+  static const intptr_t kHeaderSize = OS::kMaxPreferredCodeAlignment;
+
+ private:
+  const void* raw_memory_;  // The symbol kInstructionsSnapshot.
+
+  DISALLOW_COPY_AND_ASSIGN(InstructionsSnapshot);
+};
+
+
 class BaseReader {
  public:
   BaseReader(const uint8_t* buffer, intptr_t size) : stream_(buffer, size) {}
   // Reads raw data (for basic types).
   // sizeof(T) must be in {1,2,4,8}.
   template <typename T>
   T Read() {
     return ReadStream::Raw<sizeof(T), T>::Read(&stream_);
   }
 
@@ skipping 569 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(ForwardList);
 };
 
 
 class InstructionsWriter : public ZoneAllocated {
  public:
   InstructionsWriter(uint8_t** buffer,
                      ReAlloc alloc,
                      intptr_t initial_size)
     : stream_(buffer, alloc, initial_size),
-      next_offset_(0),
+      next_offset_(InstructionsSnapshot::kHeaderSize),
       instructions_() {
     ASSERT(buffer != NULL);
     ASSERT(alloc != NULL);
   }
 
   // Size of the snapshot.
   intptr_t BytesWritten() const { return stream_.bytes_written(); }
 
   int32_t GetOffsetFor(RawInstructions* instructions);
 
@@ skipping 17 matching lines @@
     union {
       RawInstructions* raw_insns_;
       const Instructions* insns_;
     };
     union {
       RawCode* raw_code_;
       const Code* code_;
     };
   };
 
+  void WriteWordLiteral(uword value) {
+    // Padding is helpful for comparing the .S with --disassemble.
+#if defined(ARCH_IS_64_BIT)
+    stream_.Print(".quad 0x%0.16" Px "\n", value);
+#else
+    stream_.Print(".word 0x%0.8" Px "\n", value);
+#endif
+  }
 
   WriteStream stream_;
   intptr_t next_offset_;
   GrowableArray<InstructionsData> instructions_;
 
   DISALLOW_COPY_AND_ASSIGN(InstructionsWriter);
 };
 
 
 class SnapshotWriter : public BaseWriter {
@@ skipping 257 matching lines @@
  private:
   SnapshotWriter* writer_;
   bool as_references_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriterVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_SNAPSHOT_H_