[turbofan] Change TruncateFloat32ToUint64 to TryTruncateFloat32ToUint64.

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 da9ce5fc5dccbaf26898afda8883448c88f7d378..d1359e59c4141740cbea3b0411a6cddabe1ebd5a 100644
--- a/src/compiler/ppc/instruction-selector-ppc.cc
+++ b/src/compiler/ppc/instruction-selector-ppc.cc
@@ -941,7 +941,11 @@ void InstructionSelector::VisitTryTruncateFloat64ToInt64(Node* node) {
 }
 
 
-void InstructionSelector::VisitTruncateFloat32ToUint64(Node* node) {
+void InstructionSelector::VisitTryTruncateFloat32ToUint64(Node* node) {
+  if (NodeProperties::FindProjection(node, 1)) {
+    // TODO(ppc): implement the second return value.
+    UNIMPLEMENTED();
+  }
   VisitRR(this, kPPC_DoubleToUint64, node);
 }