Only require SSE2 at minimum hardware requirement.

runtime/vm/assembler_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_ASSEMBLER_X64_H_
 #define VM_ASSEMBLER_X64_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_x64.h directly; use assembler.h instead.
 #endif
@@ skipping 257 matching lines @@
   int unresolved_near_positions_[kMaxUnresolvedBranches];
 
   friend class Assembler;
   DISALLOW_COPY_AND_ASSIGN(Label);
 };
 
 
 class CPUFeatures : public AllStatic {
  public:
   static void InitOnce();
-  static bool sse3_supported();
+  // x64 always has at least SSE2.
+  static bool sse2_supported() { return true; }
   static bool sse4_1_supported();
 
  private:
-  static const uint64_t kSSE3BitMask = static_cast<uint64_t>(1) << 32;
   static const uint64_t kSSE4_1BitMask = static_cast<uint64_t>(1) << 51;
 
-  static bool sse3_supported_;
   static bool sse4_1_supported_;
 #ifdef DEBUG
   static bool initialized_;
 #endif
 };
 
 
 class Assembler : public ValueObject {
  public:
   Assembler() : buffer_(), prolog_offset_(-1), comments_() { }
@@ skipping 482 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_X64_H_