[turbofan] Add the RoundInt32ToFloat32 operator to turbofan.

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

Index: src/compiler/mips/instruction-selector-mips.cc
diff --git a/src/compiler/mips/instruction-selector-mips.cc b/src/compiler/mips/instruction-selector-mips.cc
index 61cea76b22cc5c9a4f8a9c9f9250a3bfa7f80478..fae5962b80841b86fc302b63e20daab4d1049282 100644
--- a/src/compiler/mips/instruction-selector-mips.cc
+++ b/src/compiler/mips/instruction-selector-mips.cc
@@ -503,6 +503,11 @@ void InstructionSelector::VisitChangeFloat32ToFloat64(Node* node) {
 }
 
 
+void InstructionSelector::VisitRoundInt32ToFloat32(Node* node) {
+  VisitRR(this, kMipsCvtSW, node);
+}
+
+
 void InstructionSelector::VisitChangeInt32ToFloat64(Node* node) {
   VisitRR(this, kMipsCvtDW, node);
 }