[turbofan] Introduce TruncateTaggedToWord32 simplified 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 70518caf70f720735b801013405ddf6978812ff1..aed82f5b80a427e0adf3856cb1bc92e1b70b5606 100644
--- a/src/compiler/ppc/instruction-selector-ppc.cc
+++ b/src/compiler/ppc/instruction-selector-ppc.cc
@@ -1133,8 +1133,7 @@ void InstructionSelector::VisitTruncateFloat64ToFloat32(Node* node) {
   VisitRR(this, kPPC_DoubleToFloat32, node);
 }
 
-
-void InstructionSelector::VisitTruncateFloat64ToInt32(Node* node) {
+void InstructionSelector::VisitTruncateFloat64ToWord32(Node* node) {
   switch (TruncationModeOf(node->op())) {
     case TruncationMode::kJavaScript:
       return VisitRR(this, kArchTruncateDoubleToI, node);