[turbofan] Added the RoundInt64ToFloat64 instruction to TurboFan.

src/compiler/mips64/instruction-selector-mips64.cc

Index: src/compiler/mips64/instruction-selector-mips64.cc
diff --git a/src/compiler/mips64/instruction-selector-mips64.cc b/src/compiler/mips64/instruction-selector-mips64.cc
index 62180756ff7ecc2c163d0513ea6a9a73bdbf11d7..dbc8758c9999f9cdc5e1602121cd4d356d5e54bb 100644
--- a/src/compiler/mips64/instruction-selector-mips64.cc
+++ b/src/compiler/mips64/instruction-selector-mips64.cc
@@ -584,6 +584,11 @@ void InstructionSelector::VisitTruncateFloat64ToInt32(Node* node) {
 }
 
 
+void InstructionSelector::VisitRoundInt64ToFloat64(Node* node) {
+  VisitRR(this, kMips64CvtDL, node);
+}
+
+
 void InstructionSelector::VisitBitcastFloat32ToInt32(Node* node) {
   VisitRR(this, kMips64Float64ExtractLowWord32, node);
 }