[turbofan] Add proper conversion operators for int32<->int64.

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 9eca69610b3e3ce2a5964acca900b32725e3ee7d..b46906280ecf38bac2bb036b753a4f3f7766bf68 100644
--- a/src/compiler/arm64/instruction-selector-arm64.cc
+++ b/src/compiler/arm64/instruction-selector-arm64.cc
@@ -71,14 +71,6 @@ class Arm64OperandGenerator V8_FINAL : public OperandGenerator {
 };
 
 
-static void VisitRR(InstructionSelector* selector, ArchOpcode opcode,
-                    Node* node) {
-  Arm64OperandGenerator g(selector);
-  selector->Emit(opcode, g.DefineAsRegister(node),
-                 g.UseRegister(node->InputAt(0)));
-}
-
-
 static void VisitRRR(InstructionSelector* selector, ArchOpcode opcode,
                      Node* node) {
   Arm64OperandGenerator g(selector);
@@ -426,16 +418,6 @@ void InstructionSelector::VisitInt64UMod(Node* node) {
 }
 
 
-void InstructionSelector::VisitConvertInt32ToInt64(Node* node) {
-  VisitRR(this, kArm64Int32ToInt64, node);
-}
-
-
-void InstructionSelector::VisitConvertInt64ToInt32(Node* node) {
-  VisitRR(this, kArm64Int64ToInt32, node);
-}
-
-
 void InstructionSelector::VisitChangeInt32ToFloat64(Node* node) {
   Arm64OperandGenerator g(this);
   Emit(kArm64Int32ToFloat64, g.DefineAsDoubleRegister(node),
@@ -464,6 +446,24 @@ void InstructionSelector::VisitChangeFloat64ToUint32(Node* node) {
 }
 
 
+void InstructionSelector::VisitChangeInt32ToInt64(Node* node) {
+  Arm64OperandGenerator g(this);
+  Emit(kArm64Sxtw, g.DefineAsRegister(node), g.UseRegister(node->InputAt(0)));
+}
+
+
+void InstructionSelector::VisitChangeUint32ToUint64(Node* node) {
+  Arm64OperandGenerator g(this);
+  Emit(kArm64Mov32, g.DefineAsRegister(node), g.UseRegister(node->InputAt(0)));
+}
+
+
+void InstructionSelector::VisitTruncateInt64ToInt32(Node* node) {
+  Arm64OperandGenerator g(this);
+  Emit(kArm64Mov32, g.DefineAsRegister(node), g.UseRegister(node->InputAt(0)));
+}
+
+
 void InstructionSelector::VisitFloat64Add(Node* node) {
   VisitRRRFloat64(this, kArm64Float64Add, node);
 }