[compiler] Introduce code stubs for string relational comparisons.

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index 533641955c5ea9fa37be7a4ba4278d81bb221e7c..e49fffeb1bf353844a97afb2b83eeb8af1155db9 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -109,6 +109,10 @@ namespace internal {
   V(StrictNotEqual)                         \
   V(StringEqual)                            \
   V(StringNotEqual)                         \
+  V(StringLessThan)                         \
+  V(StringLessThanOrEqual)                  \
+  V(StringGreaterThan)                      \
+  V(StringGreaterThanOrEqual)               \
   V(ToBoolean)                              \
   /* IC Handler stubs */                    \
   V(ArrayBufferViewLoadField)               \
@@ -701,6 +705,41 @@ class StringNotEqualStub final : public TurboFanCodeStub {
   DEFINE_TURBOFAN_CODE_STUB(StringNotEqual, TurboFanCodeStub);
 };
 
+class StringLessThanStub final : public TurboFanCodeStub {
+ public:
+  explicit StringLessThanStub(Isolate* isolate) : TurboFanCodeStub(isolate) {}
+
+  DEFINE_CALL_INTERFACE_DESCRIPTOR(Compare);
+  DEFINE_TURBOFAN_CODE_STUB(StringLessThan, TurboFanCodeStub);
+};
+
+class StringLessThanOrEqualStub final : public TurboFanCodeStub {
+ public:
+  explicit StringLessThanOrEqualStub(Isolate* isolate)
+      : TurboFanCodeStub(isolate) {}
+
+  DEFINE_CALL_INTERFACE_DESCRIPTOR(Compare);
+  DEFINE_TURBOFAN_CODE_STUB(StringLessThanOrEqual, TurboFanCodeStub);
+};
+
+class StringGreaterThanStub final : public TurboFanCodeStub {
+ public:
+  explicit StringGreaterThanStub(Isolate* isolate)
+      : TurboFanCodeStub(isolate) {}
+
+  DEFINE_CALL_INTERFACE_DESCRIPTOR(Compare);
+  DEFINE_TURBOFAN_CODE_STUB(StringGreaterThan, TurboFanCodeStub);
+};
+
+class StringGreaterThanOrEqualStub final : public TurboFanCodeStub {
+ public:
+  explicit StringGreaterThanOrEqualStub(Isolate* isolate)
+      : TurboFanCodeStub(isolate) {}
+
+  DEFINE_CALL_INTERFACE_DESCRIPTOR(Compare);
+  DEFINE_TURBOFAN_CODE_STUB(StringGreaterThanOrEqual, TurboFanCodeStub);
+};
+
 class ToBooleanStub final : public TurboFanCodeStub {
  public:
   explicit ToBooleanStub(Isolate* isolate) : TurboFanCodeStub(isolate) {}