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

src/compiler/arm64/code-generator-arm64.cc

Index: src/compiler/arm64/code-generator-arm64.cc
diff --git a/src/compiler/arm64/code-generator-arm64.cc b/src/compiler/arm64/code-generator-arm64.cc
index f21462e27f03ae3456c0c27441bfe597e7a628a6..5127b1012f3dff481ac67e43f3af87124e5b5598 100644
--- a/src/compiler/arm64/code-generator-arm64.cc
+++ b/src/compiler/arm64/code-generator-arm64.cc
@@ -274,6 +274,12 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
     case kArm64Ror32:
       ASSEMBLE_SHIFT(Ror, 32);
       break;
+    case kArm64Mov32:
+      __ Mov(i.OutputRegister32(), i.InputRegister32(0));
+      break;
+    case kArm64Sxtw:
+      __ Sxtw(i.OutputRegister(), i.InputRegister32(0));
+      break;
     case kArm64CallCodeObject: {
       if (instr->InputAt(0)->IsImmediate()) {
         Handle<Code> code = Handle<Code>::cast(i.InputHeapObject(0));
@@ -383,14 +389,6 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
                        0, 2);
       break;
     }
-    case kArm64Int32ToInt64:
-      __ Sxtw(i.OutputRegister(), i.InputRegister(0));
-      break;
-    case kArm64Int64ToInt32:
-      if (!i.OutputRegister().is(i.InputRegister(0))) {
-        __ Mov(i.OutputRegister(), i.InputRegister(0));
-      }
-      break;
     case kArm64Float64ToInt32:
       __ Fcvtzs(i.OutputRegister32(), i.InputDoubleRegister(0));
       break;