[PHITransAddr] Don't assume that instruction operands are translatable

We can only PHI translate instructions.  In our attempt to PHI translate
a bitcast, we attempt to translate its operand; however, the operand
might be an argument or a global instead of an instruction.  Benignly
bail out when this happens.

This fixes PR24397.

Differential Revision: http://reviews.llvm.org/D11879

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@244418 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed