This is the reduced repro ...

var a = [function() {}, function() {}];
for (;;) { a = a.concat(a); }

Reproduces as follows ...

$ git checkout da477bc7e284f2eb07f9f79a5214525c482d3c55
$ make -j1000 x64.debug
$ out/x64.debug/d8 --random-seed=-109433610 --invoke-weak-callbacks --omit-quit test/mjsunit/foo.js

#
# Fatal error in ../src/elements.cc, line 3000
# Check failed: result_len <= FixedDoubleArray::kMaxLength.
#

==== C stack trace ===============================

 1: V8_Fatal
 2: v8::internal::ElementsAccessor::Concat(v8::internal::Isolate*, v8::internal::Arguments*, unsigned int)
 3: 0xd5b0c8
 4: 0xd5abd7
 5: 0xd41fa6
 6: 0xb6070e092a7
Illegal instruction (core dumped)

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/823224f3ee7959dc4731191439dcef2bcb16a043

commit 823224f3ee7959dc4731191439dcef2bcb16a043
Author: cbruni <cbruni@chromium.org>
Date: Tue Apr 05 15:35:08 2016

[elements] Fix length bounds precheck for Array.prototype.concat

BUG= chromium:599414 
LOG=n

Review URL: https://codereview.chromium.org/1863553003

Cr-Commit-Position: refs/heads/master@{#35269}

[modify] https://crrev.com/823224f3ee7959dc4731191439dcef2bcb16a043/src/builtins.cc
[modify] https://crrev.com/823224f3ee7959dc4731191439dcef2bcb16a043/src/elements.cc
[add] https://crrev.com/823224f3ee7959dc4731191439dcef2bcb16a043/test/mjsunit/regress/regress-599414-array-concat-fast-path.js

ClusterFuzz has detected this issue as fixed in range 35268:35269.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=6356890476347392

Fuzzer: decoder_langfuzz
Job Type: linux_asan_d8_ignition_dbg
Platform Id: linux

Crash Type: CHECK failure
Crash Address: 
Crash State:
  result_len <= FixedDoubleArray::kMaxLength in src/elements.cc
  
Fixed: V8: r35268:35269

Minimized Testcase (5.67 Kb): https://cluster-fuzz.appspot.com/download/AMIfv97-RqC_DX9LSJ_oCJxPiAEPfPzrihgL4OVOxIv7iuX9l2_-BlRnNiq0fzYoHhFl-PVmBBvvTAgP1zcjI1PbtQSaDca6EBJW7ELlYlykUVWKisAu7DMTgprsrtS8LkL8vPDQKHLookUobyq3GzFOwHGfzQ7ABg

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