[debug] add exception predictions to builtins where missing.

src/isolate.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/isolate.h"
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
@@ skipping 1333 matching lines @@
         if (code->IsCode() && code->kind() == AbstractCode::BUILTIN) {
           if (code->GetCode()->is_promise_rejection()) {
             return HandlerTable::PROMISE;
           }
 
           // This the exception throw in PromiseHandle which doesn't
           // cause a promise rejection.
           if (code->GetCode()->is_exception_caught()) {
             return HandlerTable::CAUGHT;
           }
+
+          // The built-in must be marked with an exception prediction.
+          UNREACHABLE();
         }
 
         if (code->kind() == AbstractCode::OPTIMIZED_FUNCTION) {
           DCHECK(summary.AsJavaScript().function()->shared()->asm_function());
           // asm code cannot contain try-catch.
           continue;
         }
         // Must have been constructed from a bytecode array.
         CHECK_EQ(AbstractCode::INTERPRETED_FUNCTION, code->kind());
         int code_offset = summary.code_offset();
@@ skipping 2332 matching lines @@
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8