[stubs] Refactor StringCompareStub and use it for HStringCompareAndBranch.

src/mips64/lithium-codegen-mips64.cc

Index: src/mips64/lithium-codegen-mips64.cc
diff --git a/src/mips64/lithium-codegen-mips64.cc b/src/mips64/lithium-codegen-mips64.cc
index 810414dd71df91bc050fbbccf73e5900ac86676a..4c76551138e0801aca4b23d10a913f44561e745a 100644
--- a/src/mips64/lithium-codegen-mips64.cc
+++ b/src/mips64/lithium-codegen-mips64.cc
@@ -1021,11 +1021,6 @@ void LCodeGen::DoCallStub(LCallStub* instr) {
       CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
       break;
     }
-    case CodeStub::StringCompare: {
-      StringCompareStub stub(isolate());
-      CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
-      break;
-    }
     default:
       UNREACHABLE();
   }
@@ -2563,15 +2558,14 @@ static Condition ComputeCompareCondition(Token::Value op) {
 
 void LCodeGen::DoStringCompareAndBranch(LStringCompareAndBranch* instr) {
   DCHECK(ToRegister(instr->context()).is(cp));
-  Token::Value op = instr->op();
-
-  Handle<Code> ic =
-      CodeFactory::CompareIC(isolate(), op, Strength::WEAK).code();
-  CallCode(ic, RelocInfo::CODE_TARGET, instr);
+  DCHECK(ToRegister(instr->left()).is(a1));
+  DCHECK(ToRegister(instr->right()).is(a0));
 
-  Condition condition = ComputeCompareCondition(op);
+  Handle<Code> code = CodeFactory::StringCompare(isolate()).code();
+  CallCode(code, RelocInfo::CODE_TARGET, instr);
 
-  EmitBranch(instr, condition, v0, Operand(zero_reg));
+  EmitBranch(instr, ComputeCompareCondition(instr->op()), v0,
+             Operand(zero_reg));
 }