问题
I want to remove an UnreachableInst since a previous transformation has made it reachable. However, calling eraseFromParent() gives me a malformed BasicBlock since the UnreachableInst is the terminator of its BasicBlock. How do I fix the BasicBlock to terminate at the instruction previous to the UnreachableInst?
回答1:
Every basic block must end with a terminator. I think that the most straightforward way to remove the unreachable instruction, then, is to replace it with another terminator - for example, a branch into the next basic block, a return instruction, etc.
Take a look at llvm::ReplaceInstWithInst in BasicBlockUtils.h for a convenient way to replace one instruction with another.
来源：https://stackoverflow.com/questions/18302465/llvm-remove-terminator-instruction