PPC: [compiler] Introduce StringEqualStub and StringNotEqualStub.

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

Index: src/crankshaft/ppc/lithium-codegen-ppc.cc
diff --git a/src/crankshaft/ppc/lithium-codegen-ppc.cc b/src/crankshaft/ppc/lithium-codegen-ppc.cc
index a16c92decb4fc08d05f03b3eb408afef9ddad289..d697ec45d41cb6b71fb87a9d261433ba68486a68 100644
--- a/src/crankshaft/ppc/lithium-codegen-ppc.cc
+++ b/src/crankshaft/ppc/lithium-codegen-ppc.cc
@@ -2424,9 +2424,15 @@ void LCodeGen::DoStringCompareAndBranch(LStringCompareAndBranch* instr) {
   DCHECK(ToRegister(instr->left()).is(r4));
   DCHECK(ToRegister(instr->right()).is(r3));
 
-  Handle<Code> code = CodeFactory::StringCompare(isolate()).code();
-  CallCode(code, RelocInfo::CODE_TARGET, instr);
-  __ cmpi(r3, Operand::Zero());
+  if (Token::IsOrderedRelationalCompareOp(instr->op())) {
+    Handle<Code> code = CodeFactory::StringCompare(isolate()).code();
+    CallCode(code, RelocInfo::CODE_TARGET, instr);
+    __ cmpi(r3, Operand::Zero());
+  } else {
+    Handle<Code> code = CodeFactory::StringEqual(isolate()).code();
+    CallCode(code, RelocInfo::CODE_TARGET, instr);
+    __ CompareRoot(r3, Heap::kTrueValueRootIndex);
+  }
 
   EmitBranch(instr, ComputeCompareCondition(instr->op()));
 }