[regexp] Add additional asserts to RegExp builtins

Review-Url: https://codereview.chromium.org/2799663003
Cr-Commit-Position: refs/heads/master@{#44450}

src/builtins/builtins-regexp-gen.h

@@ -58,6 +58,7 @@ class RegExpBuiltinsAssembler : public CodeStubAssembler {
                              char const* method_name);
 
   // Analogous to BranchIfFastRegExp, for use in asserts.
+  Node* IsFastRegExp(Node* const context, Node* const object);
   Node* IsFastRegExp(Node* const context, Node* const object, Node* const map);
 
   // Performs fast path checks on the given object itself, but omits prototype

src/code-stub-assembler.cc

@@ -3105,6 +3105,10 @@ Node* CodeStubAssembler::IsFixedTypedArray(Node* object) {
                            Int32Constant(LAST_FIXED_TYPED_ARRAY_TYPE)));
 }
 
+Node* CodeStubAssembler::IsJSRegExp(Node* object) {
+  return HasInstanceType(object, JS_REGEXP_TYPE);
+}
+
 Node* CodeStubAssembler::StringCharCodeAt(Node* string, Node* index,
                                           ParameterMode parameter_mode) {
   CSA_ASSERT(this, IsString(string));

src/code-stub-assembler.h

@@ -734,6 +734,7 @@ class V8_EXPORT_PRIVATE CodeStubAssembler : public compiler::CodeAssembler {
   Node* IsJSFunction(Node* object);
   Node* IsJSTypedArray(Node* object);
   Node* IsFixedTypedArray(Node* object);
+  Node* IsJSRegExp(Node* object);
 
   // ElementsKind helpers:
   Node* IsFastElementsKind(Node* elements_kind);