[CodeGenPrepare] Handle properly the promotion of operands when this does not
generate instructions.

Fixes PR21978.
Related to <rdar://problem/18310086>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224717 91177308-0d34-0410-b5e6-96231b3b80d8
[C API] Expose LLVMGetGlobalValueAddress and LLVMGetFunctionAddress.

Patch by Ramkumar Ramachandra <artagnon@gmail.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224720 91177308-0d34-0410-b5e6-96231b3b80d8