Found by Olivier Mattmann <olivier.mattmann@bluewin.ch> during work on this Master thesis where he is working on a fuzzer for C2 (see JDK-8370562).

Running java-fastdebug -Xbatch -XX:-TieredCompilation TestNpe.java yields an unexpected NPE:
Exception in thread "main" java.lang.NullPointerException: Cannot read field "c" because "<local1>.b" is null
at TestNpe.test(TestNpe.java:96)
at TestNpe.main(TestNpe.java:27)

However, running java-fastdebug -Xint TestNpe.java does not throw such an exception, hinting at a wrong execution.

Build search narrowed the causing commit down to JDK-8367627.