Enable Float32Array_getIndexed on X64 now that cvtss2sd is implemented

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 354 matching lines @@
 
   void addsd(XmmRegister dst, XmmRegister src);
   void subsd(XmmRegister dst, XmmRegister src);
   void mulsd(XmmRegister dst, XmmRegister src);
   void divsd(XmmRegister dst, XmmRegister src);
 
   void comisd(XmmRegister a, XmmRegister b);
   void cvtsi2sd(XmmRegister a, Register b);
   void cvttsd2siq(Register dst, XmmRegister src);
 
+  void cvtss2sd(XmmRegister dst, XmmRegister src);
+  void cvtsd2ss(XmmRegister dst, XmmRegister src);
+
   void xchgl(Register dst, Register src);
   void xchgq(Register dst, Register src);
 
   void cmpl(Register reg, const Immediate& imm);
   void cmpl(Register reg0, Register reg1);
   void cmpl(Register reg, const Address& address);
   void cmpl(const Address& address, const Immediate& imm);
 
   void cmpq(Register reg, const Immediate& imm);
   void cmpq(const Address& address, Register reg);
@@ skipping 342 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_X64_H_