The object materialization in the deoptimizer is missing the {JS_STRING_ITERATOR_TYPE} instance type. Kudos to Jaro for the excellent debug messages!

Jaro agreed to take a look.

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/6d1894e4f4a63a165b5bfcae414bd7137e01f8d9

commit 6d1894e4f4a63a165b5bfcae414bd7137e01f8d9
Author: jarin <jarin@chromium.org>
Date: Mon Jan 23 16:46:42 2017

[deoptimizer] Materialize string iterators.

BUG= chromium:683617 

Review-Url: https://codereview.chromium.org/2651553003
Cr-Commit-Position: refs/heads/master@{#42606}

[modify] https://crrev.com/6d1894e4f4a63a165b5bfcae414bd7137e01f8d9/src/deoptimizer.cc
[add] https://crrev.com/6d1894e4f4a63a165b5bfcae414bd7137e01f8d9/test/mjsunit/regress/regress-683617.js

ClusterFuzz has detected this issue as fixed in range 42605:42606.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=6005687605002240

Fuzzer: mbarbella_js_mutation
Job Type: linux_asan_d8_ignition_turbo_dbg
Platform Id: linux

Crash Type: Unreachable code
Crash Address: 
Crash State:
  deoptimizer.cc
  
Sanitizer: address (ASAN)

Regressed: V8: 42446:42447
Fixed: V8: 42605:42606

Minimized Testcase (0.20 Kb):
Download: https://cluster-fuzz.appspot.com/download/AMIfv97x633RpvpHtJ2ENngQbncA7UgMKe7l_zIrT0jWhFbri2De6Sb9H3mWybAfw5EjmBrmrqB2cJ74M44uv0-kY04gg7iIvB7AOak065_SGy3Fnqvp_O36lUBWVT4Mb275HE4xqUrDv80ULwsj4SnJCmQSzLjWAF808Nuzs-s6NUyhwW6gHNbMBbnaWTi1wmDRrL1-SWnZJ2_N06qGyBSUJ-j3UQFp0_hU-FhA8tk2q2QYSlQZHTPgWUvx_pj_pCMRmyynaJsPUKauJb3PBXoHJdwDNAGz-gbcNK2Jv7zGye2_DrILVRJtclMTnQWWIy7ZcAy3AXg5qTBarrywUeLWYOTj5RO_iEa5xNz-W8RqCwEDnh2Kf-M?testcase_id=6005687605002240
__v_0 = "//" + new Array();
function __f_0(deopt) {
  let __v_1 = __v_0[Symbol.iterator]();
  if (deopt) {
    return __v_1.next().value;
  }
}
__f_0();
__f_0();
%OptimizeFunctionOnNextCall(__f_0);
__f_0(true)


Additional requirements: Requires Gestures

See https://dev.chromium.org/Home/chromium-security/bugs/reproducing-clusterfuzz-bugs for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.