[compiler] Introduce code stubs for string relational comparisons.

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 5bfa347a320820a8fae7a75c41d1bb635a371ca6..7dbac5d125e97a6f9888c21622f7ce4e6b2ecf29 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -2817,45 +2817,6 @@ void StringHelper::GenerateOneByteCharsCompareLoop(
 }
 
 
-void StringCompareStub::Generate(MacroAssembler* masm) {
-  // ----------- S t a t e -------------
-  //  -- rdx    : left string
-  //  -- rax    : right string
-  //  -- rsp[0] : return address
-  // -----------------------------------
-  __ AssertString(rdx);
-  __ AssertString(rax);
-
-  // Check for identity.
-  Label not_same;
-  __ cmpp(rdx, rax);
-  __ j(not_equal, &not_same, Label::kNear);
-  __ Move(rax, Smi::FromInt(EQUAL));
-  __ IncrementCounter(isolate()->counters()->string_compare_native(), 1);
-  __ Ret();
-
-  __ bind(&not_same);
-
-  // Check that both are sequential one-byte strings.
-  Label runtime;
-  __ JumpIfNotBothSequentialOneByteStrings(rdx, rax, rcx, rbx, &runtime);
-
-  // Inline comparison of one-byte strings.
-  __ IncrementCounter(isolate()->counters()->string_compare_native(), 1);
-  StringHelper::GenerateCompareFlatOneByteStrings(masm, rdx, rax, rcx, rbx, rdi,
-                                                  r8);
-
-  // Call the runtime; it returns -1 (less), 0 (equal), or 1 (greater)
-  // tagged as a small integer.
-  __ bind(&runtime);
-  __ PopReturnAddressTo(rcx);
-  __ Push(rdx);
-  __ Push(rax);
-  __ PushReturnAddressFrom(rcx);
-  __ TailCallRuntime(Runtime::kStringCompare);
-}
-
-
 void BinaryOpICWithAllocationSiteStub::Generate(MacroAssembler* masm) {
   // ----------- S t a t e -------------
   //  -- rdx    : left