Fixes https://github.com/llvm/llvm-project/issues/56807
The problem occurs when the InstCombine pass removes an unnecessary BitCast but does not update the operand of the llvm.dbg.declare intrinsic call. This makes the llvm.dbg.declare have undef as its operand, but the problem can go away if we replace debug uses of the old alloca in the new alloca.
Before this PR, the first argument used to be "undef"