InstanceOfStub incorrectly interprets the hole as a prototype.

src/mips/code-stubs-mips.cc

Index: src/mips/code-stubs-mips.cc
diff --git a/src/mips/code-stubs-mips.cc b/src/mips/code-stubs-mips.cc
index 5062cc3b9aad7d47937dd4049294f48e8d82268a..ab06a7100ce8d652ffbda1bc460909dc14cb8a6f 100644
--- a/src/mips/code-stubs-mips.cc
+++ b/src/mips/code-stubs-mips.cc
@@ -1503,8 +1503,12 @@ void InstanceOfStub::Generate(MacroAssembler* masm) {
   __ GetObjectType(function, function_map, scratch);
   __ Branch(&slow_case, ne, scratch, Operand(JS_FUNCTION_TYPE));
 
-  // Ensure that {function} has an instance prototype.
+  // Go to the runtime if the function is not a constructor.
   __ lbu(scratch, FieldMemOperand(function_map, Map::kBitFieldOffset));
+  __ And(at, scratch, Operand(1 << Map::kIsConstructor));
+  __ Branch(&slow_case, eq, at, Operand(zero_reg));
+
+  // Ensure that {function} has an instance prototype.
   __ And(at, scratch, Operand(1 << Map::kHasNonInstancePrototype));
   __ Branch(&slow_case, ne, at, Operand(zero_reg));