In CoroFrame, we collect lifetime marker of an alloca by collect the user of BitCast who is the user of the alloca. However, either the alloca itself could be used with the lifetime marker or the BitCast of the alloca could be transformed to other instructions. (e.g., it may be transformed to all zero reps in InstCombine pass). This patch tries to fix these two little bugs.
TestPlan: cppcoro, check-llvm