Correctify instanceof and make it optimizable.

src/full-codegen/mips/full-codegen-mips.cc

Index: src/full-codegen/mips/full-codegen-mips.cc
diff --git a/src/full-codegen/mips/full-codegen-mips.cc b/src/full-codegen/mips/full-codegen-mips.cc
index 7c5fc5ae91fa377514175975ac9227e7accced6b..b39f698e4a8b5b39a958d0751efcba0f4d3af636 100644
--- a/src/full-codegen/mips/full-codegen-mips.cc
+++ b/src/full-codegen/mips/full-codegen-mips.cc
@@ -5118,12 +5118,14 @@ void FullCodeGenerator::VisitCompareOperation(CompareOperation* expr) {
       break;
 
     case Token::INSTANCEOF: {
-      VisitForStackValue(expr->right());
-      InstanceofStub stub(isolate(), InstanceofStub::kNoFlags);
+      VisitForAccumulatorValue(expr->right());
+      __ mov(a0, result_register());
+      __ pop(a1);
+      InstanceOfStub stub(isolate());
       __ CallStub(&stub);
-      PrepareForBailoutBeforeSplit(expr, true, if_true, if_false);
-      // The stub returns 0 for true.
-      Split(eq, v0, Operand(zero_reg), if_true, if_false, fall_through);
+      PrepareForBailoutBeforeSplit(expr, false, NULL, NULL);
+      __ LoadRoot(at, Heap::kTrueValueRootIndex);
+      Split(eq, v0, Operand(at), if_true, if_false, fall_through);
       break;
     }