[DebugInfo] Maintain DI for sunken bitcasts

When a bitcast is being sunk in -codegenprepare pass, its DI wasn't
copied over to the newly created instruction. This patch fixes that
bug.

Patch by Kareem Ergawy!

Differential Revision: https://reviews.llvm.org/D47282

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@333133 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed