X87: [compiler] Introduce StringEqualStub and StringNotEqualStub.

src/crankshaft/x87/lithium-codegen-x87.cc

Index: src/crankshaft/x87/lithium-codegen-x87.cc
diff --git a/src/crankshaft/x87/lithium-codegen-x87.cc b/src/crankshaft/x87/lithium-codegen-x87.cc
index e7ced921ef31f7b9ec528b00e3efd480b00c174a..bf39b7f84eda6d5fab54dc72754c0df99a493bdc 100644
--- a/src/crankshaft/x87/lithium-codegen-x87.cc
+++ b/src/crankshaft/x87/lithium-codegen-x87.cc
@@ -2452,9 +2452,15 @@ void LCodeGen::DoStringCompareAndBranch(LStringCompareAndBranch* instr) {
   DCHECK(ToRegister(instr->left()).is(edx));
   DCHECK(ToRegister(instr->right()).is(eax));
 
-  Handle<Code> code = CodeFactory::StringCompare(isolate()).code();
-  CallCode(code, RelocInfo::CODE_TARGET, instr);
-  __ test(eax, eax);
+  if (Token::IsOrderedRelationalCompareOp(instr->op())) {
+    Handle<Code> code = CodeFactory::StringCompare(isolate()).code();
+    CallCode(code, RelocInfo::CODE_TARGET, instr);
+    __ test(eax, eax);
+  } else {
+    Handle<Code> code = CodeFactory::StringEqual(isolate()).code();
+    CallCode(code, RelocInfo::CODE_TARGET, instr);
+    __ CompareRoot(eax, Heap::kTrueValueRootIndex);
+  }
 
   EmitBranch(instr, ComputeCompareCondition(instr->op()));
 }