[llvm-dev] Calling LowerSwitchPass causing crash in llvm 9

n3v3rm03 via llvm-dev llvm-dev at lists.llvm.org
Thu Dec 26 23:10:26 PST 2019

No, I'm not talking about object code, I'm talking about llvm-ir. And there
IS "switch" instruction in llvm-ir.

2019年12月27日(金) 15:50 mayuyu.io <admin at mayuyu.io>:

> There is no “switch” instruction in the target object code. It usually
> gets compiled into a switch table with instructions to load from it. Afaik
> Zhang
> 在 2019年12月26日,17:49,n3v3rm03 via llvm-dev <llvm-dev at lists.llvm.org> 写道:
> Sorry I found an early thread discussing this question. I guess I
> shouldn't create lower switch pass like this.
> However, I have another question, even if I don't  call this pass, the
> switch instructions will be finally compiled into binary trees, is that
> correct?
> It seems only AMDGPU is using this pass. Is there any rule to call this
> pass or not?
> On Thu, Dec 26, 2019 at 6:36 PM n3v3rm03 <n3v3rm03 at gmail.com> wrote:
>> Hi,
>> I am trying to call LowerSwitchPass directly in my custom pass in this
>> way:
>>   FunctionPass *lower = createLowerSwitchPass();
>>   lower->runOnFunction(*f);
>> But it will crash when running lower->runOnFunction(*f) in llvm-9.
>> I was using this method in llvm-8 and it worked fine. It seems the crash
>> happens at the first line of the LowerSwitch::runOnFunction(Function &F) in
>> the newer llvm:
>> LazyValueInfo *LVI = &getAnalysis<LazyValueInfoWrapperPass>().getLVI();
>> //crashed here
>> I can't figure out why this usage cause the compiler to crash? Am I
>> calling function pass wrong?
>> Thank you for your help.
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