[compiler] Introduce code stubs for string relational comparisons.

src/crankshaft/arm64/lithium-codegen-arm64.cc

Index: src/crankshaft/arm64/lithium-codegen-arm64.cc
diff --git a/src/crankshaft/arm64/lithium-codegen-arm64.cc b/src/crankshaft/arm64/lithium-codegen-arm64.cc
index 6e9d604be8a074026a7f5e538330de3cd0b43be2..77f55145260eb4a7bfd55f9f01640508f3321426 100644
--- a/src/crankshaft/arm64/lithium-codegen-arm64.cc
+++ b/src/crankshaft/arm64/lithium-codegen-arm64.cc
@@ -5193,18 +5193,10 @@ void LCodeGen::DoStringCompareAndBranch(LStringCompareAndBranch* instr) {
   DCHECK(ToRegister(instr->left()).is(x1));
   DCHECK(ToRegister(instr->right()).is(x0));
 
-  if (Token::IsOrderedRelationalCompareOp(instr->op())) {
-    Handle<Code> code = CodeFactory::StringCompare(isolate()).code();
-    CallCode(code, RelocInfo::CODE_TARGET, instr);
-
-    EmitCompareAndBranch(instr, TokenToCondition(instr->op(), false), x0, 0);
-  } else {
-    Handle<Code> code = CodeFactory::StringEqual(isolate()).code();
-    CallCode(code, RelocInfo::CODE_TARGET, instr);
-    __ CompareRoot(x0, Heap::kTrueValueRootIndex);
-
-    EmitBranch(instr, TokenToCondition(instr->op(), false));
-  }
+  Handle<Code> code = CodeFactory::StringCompare(isolate(), instr->op()).code();
+  CallCode(code, RelocInfo::CODE_TARGET, instr);
+  __ CompareRoot(x0, Heap::kTrueValueRootIndex);
+  EmitBranch(instr, eq);
 }