This applies to memory accesses to (compile-time) constant addresses
(such as memory-mapped registers). Currently when a misaligned access
to such an address is detected, a fatal error is reported. This change
will emit a remark, and the compilation will continue with a trap,
and "undef" (for loads) emitted.
This fixes https://llvm.org/PR50838.
Differential Revision: https://reviews.llvm.org/D50524
94e01d579c