[compiler] Introduce StringEqualStub and StringNotEqualStub.

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index 595769d173371e415a8fb117bbfe1ac4fd2e8b5d..fbed23f84720b6ecb7af42346f844a00ca19fdd4 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -103,6 +103,8 @@ namespace internal {
   V(StringLength)                           \
   V(StrictEqual)                            \
   V(StrictNotEqual)                         \
+  V(StringEqual)                            \
+  V(StringNotEqual)                         \
   V(ToBoolean)                              \
   /* IC Handler stubs */                    \
   V(ArrayBufferViewLoadField)               \
@@ -653,6 +655,26 @@ class StrictNotEqualStub final : public TurboFanCodeStub {
   DEFINE_CODE_STUB(StrictNotEqual, TurboFanCodeStub);
 };
 
+class StringEqualStub final : public TurboFanCodeStub {
+ public:
+  explicit StringEqualStub(Isolate* isolate) : TurboFanCodeStub(isolate) {}
+
+  void GenerateAssembly(compiler::CodeStubAssembler* assembler) const final;
+
+  DEFINE_CALL_INTERFACE_DESCRIPTOR(Compare);
+  DEFINE_CODE_STUB(StringEqual, TurboFanCodeStub);
+};
+
+class StringNotEqualStub final : public TurboFanCodeStub {
+ public:
+  explicit StringNotEqualStub(Isolate* isolate) : TurboFanCodeStub(isolate) {}
+
+  void GenerateAssembly(compiler::CodeStubAssembler* assembler) const final;
+
+  DEFINE_CALL_INTERFACE_DESCRIPTOR(Compare);
+  DEFINE_CODE_STUB(StringNotEqual, TurboFanCodeStub);
+};
+
 class ToBooleanStub final : public TurboFanCodeStub {
  public:
   explicit ToBooleanStub(Isolate* isolate) : TurboFanCodeStub(isolate) {}