[cleanup] Remove is_null from tnode.h

Instead of checking for the null TNode, we can use base::Optional.

Bug: v8:6949
Change-Id: I550b2fdb507c61ea6128a0631351b22a8542d4d3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2737296
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73260}

src/codegen/tnode.h

@@ -347,8 +347,6 @@ class TNode {
     return *this;
   }
 
-  bool is_null() const { return node_ == nullptr; }
-
   operator compiler::Node*() const { return node_; }
 
   static TNode UncheckedCast(compiler::Node* node) { return TNode(node); }

src/compiler/code-assembler.cc

@@ -1088,7 +1088,7 @@ Node* CodeAssembler::CallStubRImpl(StubCallMode call_mode,
 Node* CodeAssembler::CallJSStubImpl(const CallInterfaceDescriptor& descriptor,
                                     TNode<Object> target, TNode<Object> context,
                                     TNode<Object> function,
-                                    TNode<Object> new_target,
+                                    base::Optional<TNode<Object>> new_target,
                                     TNode<Int32T> arity,
                                     std::initializer_list<Node*> args) {
   constexpr size_t kMaxNumArgs = 10;
@@ -1096,8 +1096,8 @@ Node* CodeAssembler::CallJSStubImpl(const CallInterfaceDescriptor& descriptor,
   NodeArray<kMaxNumArgs + 5> inputs;
   inputs.Add(target);
   inputs.Add(function);
-  if (!new_target.is_null()) {
-    inputs.Add(new_target);
+  if (new_target) {
+    inputs.Add(*new_target);
   }
   inputs.Add(arity);
   for (auto arg : args) inputs.Add(arg);

src/compiler/code-assembler.h

@@ -14,6 +14,7 @@
 // Do not include anything from src/compiler here!
 #include "include/cppgc/source-location.h"
 #include "src/base/macros.h"
+#include "src/base/optional.h"
 #include "src/base/type-traits.h"
 #include "src/builtins/builtins.h"
 #include "src/codegen/code-factory.h"
@@ -1136,8 +1137,7 @@ class V8_EXPORT_PRIVATE CodeAssembler {
     TNode<Int32T> arity = Int32Constant(argc);
     TNode<Code> target = HeapConstant(callable.code());
     return CAST(CallJSStubImpl(callable.descriptor(), target, CAST(context),
-                               CAST(function), TNode<Object>(), arity,
-                               {receiver, args...}));
+                               CAST(function), {}, arity, {receiver, args...}));
   }
 
   template <class... TArgs>
@@ -1267,7 +1267,8 @@ class V8_EXPORT_PRIVATE CodeAssembler {
 
   Node* CallJSStubImpl(const CallInterfaceDescriptor& descriptor,
                        TNode<Object> target, TNode<Object> context,
-                       TNode<Object> function, TNode<Object> new_target,
+                       TNode<Object> function,
+                       base::Optional<TNode<Object>> new_target,
                        TNode<Int32T> arity, std::initializer_list<Node*> args);
 
   Node* CallStubN(StubCallMode call_mode,

src/compiler/js-call-reducer.cc

@@ -1479,12 +1479,12 @@ struct MapFrameStateParams {
   TNode<Object> receiver;
   TNode<Object> callback;
   TNode<Object> this_arg;
-  TNode<JSArray> a;
+  base::Optional<TNode<JSArray>> a;
   TNode<Object> original_length;
 };
 
 FrameState MapPreLoopLazyFrameState(const MapFrameStateParams& params) {
-  DCHECK(params.a.is_null());
+  DCHECK(!params.a);
   Node* checkpoint_params[] = {params.receiver, params.callback,
                                params.this_arg, params.original_length};
   return CreateJavaScriptBuiltinContinuationFrameState(
@@ -1497,7 +1497,7 @@ FrameState MapPreLoopLazyFrameState(const MapFrameStateParams& params) {
 FrameState MapLoopLazyFrameState(const MapFrameStateParams& params,
                                  TNode<Number> k) {
   Node* checkpoint_params[] = {
-      params.receiver,       params.callback, params.this_arg, params.a, k,
+      params.receiver,       params.callback, params.this_arg, *params.a, k,
       params.original_length};
   return CreateJavaScriptBuiltinContinuationFrameState(
       params.jsgraph, params.shared,
@@ -1509,7 +1509,7 @@ FrameState MapLoopLazyFrameState(const MapFrameStateParams& params,
 FrameState MapLoopEagerFrameState(const MapFrameStateParams& params,
                                   TNode<Number> k) {
   Node* checkpoint_params[] = {
-      params.receiver,       params.callback, params.this_arg, params.a, k,
+      params.receiver,       params.callback, params.this_arg, *params.a, k,
       params.original_length};
   return CreateJavaScriptBuiltinContinuationFrameState(
       params.jsgraph, params.shared,