[LLVMdev] JumpThreading and @llvm.dbg.declare()

[Karl-Johan Karlsson]

On 02/05/2015 08:21 PM, Hans Wennborg wrote:
> On Thu, Feb 5, 2015 at 4:49 AM, Karl-Johan Karlsson
> <karl-johan.karlsson at ericsson.com> wrote:
>> I have a small issue with the JumpThreading pass (in opt). As described in
>> the code (JumpThreading.cpp), the pass may if certain criteria are fulfilled
>> duplicate the content of a block. If the duplicated block contain a call to
>> @llvm.dbg.declare() you will end up with invalid code as the intrinsic
>> @llvm.dbg.declare() only should occur once for each variable.
>>
>> I think the JumpThreading pass should lower all llvm.dbg.declare() into
>> llvm.dbg.value() the same way as the instcombine pass do (see
>> InstructionCombining.cpp):
>>
>>    // Lower dbg.declare intrinsics otherwise their value may be clobbered
>>    // by instcombiner.
>>    bool DbgDeclaresChanged = LowerDbgDeclare(F);
>>
>> Do you agree? Ok to commit?
>
> Did you forget to attach a patch? A patch with a test case showing the
> problem you're describing would be great.
>
> Also, patches should generally be sent to the llvm-commits list, not llvmdev.

I will create a patch with a testcase and send it to llvm-commits.

Regards
/ Karl-Johan Karlsson

>
> Thanks,
> Hans
>
>