[turbofan] Added the RoundInt64ToFloat64 instruction to TurboFan.

src/compiler/x64/code-generator-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/code-generator.h"
 
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/osr.h"
@@ skipping 921 matching lines @@
       __ AssertZeroExtended(i.OutputRegister());
       break;
     }
     case kSSEInt32ToFloat64:
       if (instr->InputAt(0)->IsRegister()) {
         __ Cvtlsi2sd(i.OutputDoubleRegister(), i.InputRegister(0));
       } else {
         __ Cvtlsi2sd(i.OutputDoubleRegister(), i.InputOperand(0));
       }
       break;
+    case kSSEInt64ToFloat64:
+      if (instr->InputAt(0)->IsRegister()) {
+        __ Cvtqsi2sd(i.OutputDoubleRegister(), i.InputRegister(0));
+      } else {
+        __ Cvtqsi2sd(i.OutputDoubleRegister(), i.InputOperand(0));
+      }
+      break;
     case kSSEUint32ToFloat64:
       if (instr->InputAt(0)->IsRegister()) {
         __ movl(kScratchRegister, i.InputRegister(0));
       } else {
         __ movl(kScratchRegister, i.InputOperand(0));
       }
       __ Cvtqsi2sd(i.OutputDoubleRegister(), kScratchRegister);
       break;
     case kSSEFloat64ExtractLowWord32:
       if (instr->InputAt(0)->IsDoubleStackSlot()) {
@@ skipping 879 matching lines @@
     int padding_size = last_lazy_deopt_pc_ + space_needed - current_pc;
     __ Nop(padding_size);
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8