[turbofan] Implemented the optional Float32RoundDown operator.

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

Index: src/compiler/ppc/instruction-selector-ppc.cc
diff --git a/src/compiler/ppc/instruction-selector-ppc.cc b/src/compiler/ppc/instruction-selector-ppc.cc
index 841d34d6af088d94cbf31ad27cfff769e16bcda4..3dde93e442bbdb35ba16166c4d9016a91d3e560a 100644
--- a/src/compiler/ppc/instruction-selector-ppc.cc
+++ b/src/compiler/ppc/instruction-selector-ppc.cc
@@ -1128,6 +1128,9 @@ void InstructionSelector::VisitFloat64Sqrt(Node* node) {
 }
 
 
+void InstructionSelector::VisitFloat32RoundDown(Node* node) { UNIMPLEMENTED(); }
+
+
 void InstructionSelector::VisitFloat64RoundDown(Node* node) {
   VisitRR(this, kPPC_FloorDouble, node);
 }