[turbofan] Implemented the optional Float32RoundTruncate operator.

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 c66649809213bc55589d59087e77e7ea3250061c..a7bd22f02d654bfc662a49305fe13571222a053d 100644
--- a/src/compiler/mips64/instruction-selector-mips64.cc
+++ b/src/compiler/mips64/instruction-selector-mips64.cc
@@ -997,6 +997,11 @@ void InstructionSelector::VisitFloat64RoundUp(Node* node) {
 }
 
 
+void InstructionSelector::VisitFloat32RoundTruncate(Node* node) {
+  UNREACHABLE();
+}
+
+
 void InstructionSelector::VisitFloat64RoundTruncate(Node* node) {
   VisitRR(this, kMips64Float64RoundTruncate, node);
 }