We should ensure the size of the variable `a` is 8 bytes. Otherwise, this
generates a stack buffer overflow inside the memcpy call in 32 bits machines.
(We write more bytes than the size of a, when it is 4 bytes)
Differential Revision: https://reviews.llvm.org/D29602
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294378 91177308-0d34-0410-b5e6-96231b3b80d8