Implemented the RoundInt64ToFloat32 TurboFan operator for x64, arm64, and mips64.

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

 // Copyright 2014 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/base/adapters.h"
 #include "src/base/bits.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
@@ skipping 574 matching lines @@
   switch (TruncationModeOf(node->op())) {
     case TruncationMode::kJavaScript:
       return VisitRR(this, kArchTruncateDoubleToI, node);
     case TruncationMode::kRoundToZero:
       return VisitRR(this, kMips64TruncWD, node);
   }
   UNREACHABLE();
 }
 
 
+void InstructionSelector::VisitRoundInt64ToFloat32(Node* node) {
+  VisitRR(this, kMips64CvtSL, node);
+}
+
+
 void InstructionSelector::VisitRoundInt64ToFloat64(Node* node) {
   VisitRR(this, kMips64CvtDL, node);
 }
 
 
 void InstructionSelector::VisitBitcastFloat32ToInt32(Node* node) {
   VisitRR(this, kMips64Float64ExtractLowWord32, node);
 }
 
 
@@ skipping 751 matching lines @@
          MachineOperatorBuilder::kFloat64Max |
          MachineOperatorBuilder::kFloat32Min |
          MachineOperatorBuilder::kFloat32Max |
          MachineOperatorBuilder::kFloat64RoundDown |
          MachineOperatorBuilder::kFloat64RoundTruncate;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8