[compiler] Introduce StringEqualStub and StringNotEqualStub.

src/crankshaft/ia32/lithium-codegen-ia32.cc

Index: src/crankshaft/ia32/lithium-codegen-ia32.cc
diff --git a/src/crankshaft/ia32/lithium-codegen-ia32.cc b/src/crankshaft/ia32/lithium-codegen-ia32.cc
index f292b949daf4f8f00383d2daa052bf5bbda2c73b..2ba7b3fa0ac913d8d8b80c8f84858deddbd22a61 100644
--- a/src/crankshaft/ia32/lithium-codegen-ia32.cc
+++ b/src/crankshaft/ia32/lithium-codegen-ia32.cc
@@ -2168,9 +2168,15 @@ 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()));
 }