After JDK-8357601, we hit assertions on Big Endian platforms:
assert(verify_guards()) failed: Expected valid memory guards

V [libjvm.so+0x136892c] GuardedMemory::wrap_copy(void const*, unsigned long, void const*, void const*)+0x23c (guardedMemory.hpp:219)
V [libjvm.so+0x1674a64] checked_jni_GetStringUTFChars+0x184
C [libjava.so+0x12a80]

Product builds also run into failures:
ReleaseStringUTFChars: release chars failed bounds check. string: 0x0000000110239270 chars: 0x0000000114343508
GuardedMemory(0x0000000110239058) base_addr=0x00000001143434e0 tag=0x0000000048124812 tag2=0x0000000000000000 user_size=6 user_data=0x0000000114343508
  Header guard @0x00000001143434e0 is BROKEN
  Trailer guard @0x000000011434350e is BROKEN
  User data appears to be in use
FATAL ERROR in native method: ReleaseStringUTFChars: release chars failed bounds check.
at java.lang.Class.getPrimitiveClass(java.base/Native Method)
at java.lang.Float.<clinit>(java.base/Float.java:178)
at java.lang.Math.<clinit>(java.base/Math.java:2043)
at java.util.ImmutableCollections$SetN.probe(java.base/ImmutableCollections.java:1253)
at java.util.ImmutableCollections$SetN.<init>(java.base/ImmutableCollections.java:1162)
at java.util.Set.of(java.base/Set.java:505)
at jdk.internal.reflect.ReflectionFactory.<clinit>(java.base/ReflectionFactory.java:371)
at java.lang.reflect.AccessibleObject.<clinit>(java.base/AccessibleObject.java:487)

SafeFetch32 is used which puts the wrong value into the least significant Byte on Big Endian platforms.

In addition, SafeFetch32 looks wrong for platforms which don't support unaligned accesses.