[turbofan] Introduce TruncateTaggedToWord32 simplified operator.

src/compiler/arm64/instruction-selector-arm64.cc

Index: src/compiler/arm64/instruction-selector-arm64.cc
diff --git a/src/compiler/arm64/instruction-selector-arm64.cc b/src/compiler/arm64/instruction-selector-arm64.cc
index 59285c034ab1d16d79e587457204a3540567fc6f..9000888e3043fcd1c0c2d6f7bad359d0f504656c 100644
--- a/src/compiler/arm64/instruction-selector-arm64.cc
+++ b/src/compiler/arm64/instruction-selector-arm64.cc
@@ -1407,15 +1407,12 @@ void InstructionSelector::VisitTruncateFloat64ToFloat32(Node* node) {
   VisitRR(this, kArm64Float64ToFloat32, 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, kArm64Float64ToInt32, node);
-  }
-  UNREACHABLE();
+void InstructionSelector::VisitRoundFloat64ToInt32(Node* node) {
+  VisitRR(this, kArm64Float64ToInt32, node);
 }