In r242510, non-instrumented allocas are now moved into the first basic block. This patch limits that to:
- Only move allocas that were originally in the first basic block.
- Only move allocas that are present *after* the first instrumented one (i.e. only move allocas up).
A testcase was updated to show behavior in these two cases. Without the patch, an alloca could be moved down, and could cause an invalid IR.