[turbofan] Implemented the optional Float32RoundTruncate 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 d6d8aa7598ca90a15ffcb487f7c3b1fdd3b73c71..90d399afae7d884aeb8334a7df26ced74c38f9b6 100644
--- a/src/compiler/ppc/instruction-selector-ppc.cc
+++ b/src/compiler/ppc/instruction-selector-ppc.cc
@@ -1144,6 +1144,11 @@ void InstructionSelector::VisitFloat64RoundUp(Node* node) {
 }
 
 
+void InstructionSelector::VisitFloat32RoundTruncate(Node* node) {
+  UNREACHABLE();
+}
+
+
 void InstructionSelector::VisitFloat64RoundTruncate(Node* node) {
   VisitRR(this, kPPC_TruncateDouble, node);
 }