Prevent calls to __jit_debug_register_code from being optimized out.

Patch by Andrew MacPherson. I just tweaked the comment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199350 91177308-0d34-0410-b5e6-96231b3b80d8
BasicAA: We need to check both access sizes when comparing a gep and an
underlying object of unknown size.

Fixes PR18460.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199351 91177308-0d34-0410-b5e6-96231b3b80d8