[turbofan] Implemented the optional Float32RoundDown operator.

src/compiler/x87/instruction-selector-x87.cc

Index: src/compiler/x87/instruction-selector-x87.cc
diff --git a/src/compiler/x87/instruction-selector-x87.cc b/src/compiler/x87/instruction-selector-x87.cc
index af3889228a64ba432f708b3645ac81cccea80293..ff0cf182f83da45515ccc057a6179a917414f139 100644
--- a/src/compiler/x87/instruction-selector-x87.cc
+++ b/src/compiler/x87/instruction-selector-x87.cc
@@ -842,6 +842,9 @@ void InstructionSelector::VisitFloat64Sqrt(Node* node) {
 }
 
 
+void InstructionSelector::VisitFloat32RoundDown(Node* node) { UNIMPLEMENTED(); }
+
+
 void InstructionSelector::VisitFloat64RoundDown(Node* node) {
   X87OperandGenerator g(this);
   Emit(kX87Float64Round | MiscField::encode(kRoundDown),