[turbofan] Introduce TruncateTaggedToWord32 simplified operator.

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

Index: src/compiler/arm/instruction-selector-arm.cc
diff --git a/src/compiler/arm/instruction-selector-arm.cc b/src/compiler/arm/instruction-selector-arm.cc
index 8d11c1d82647a98a63146f29db11e568097f5449..b8d2d905e45681b9933250f3a27e78e35593f82c 100644
--- a/src/compiler/arm/instruction-selector-arm.cc
+++ b/src/compiler/arm/instruction-selector-arm.cc
@@ -1142,15 +1142,12 @@ void InstructionSelector::VisitTruncateFloat64ToFloat32(Node* node) {
   VisitRR(this, kArmVcvtF32F64, node);
 }
 
+void InstructionSelector::VisitTruncateFloat64ToWord32(Node* node) {
+  VisitRR(this, kArchTruncateDoubleToI, node);
+}
 
-void InstructionSelector::VisitTruncateFloat64ToInt32(Node* node) {
-  switch (TruncationModeOf(node->op())) {
-    case TruncationMode::kJavaScript:
-      return VisitRR(this, kArchTruncateDoubleToI, node);
-    case TruncationMode::kRoundToZero:
-      return VisitRR(this, kArmVcvtS32F64, node);
-  }
-  UNREACHABLE();
+void InstructionSelector::VisitRoundFloat64ToInt32(Node* node) {
+  VisitRR(this, kArmVcvtS32F64, node);
 }