[llvm] r340997 - [SimplifyCFG] Common debug handling [NFC]

[Philip Reames via llvm-commits]

JFYI: This was reverted by Martin in 341031.  There's a bit more 
discussion in that thread.


On 08/29/2018 08:41 PM, Philip Reames via llvm-commits wrote:
> I am away from keyboard for the rest of the day.  Please revert the 
> patch.  If you don't get to it tonight, I'll do tomorrow morning.
>
> Philip
>
> On 08/29/2018 08:37 PM, Maxim Kuvyrkov wrote:
>> Hi Philip,
>>
>> This change seems to cause clang crash when building linux kernel on 
>> aarch64.  Would you please investigate?
>>
>> Full artifacts of bisection are at [1], but most interesting parts to 
>> help you reproduce are below:
>>
>> - grep for "clang-8" in 
>> https://ci.linaro.org/view/tcwg-llvm-kernel/job/tcwg-llvm-kernel-bisect-aarch64/9/artifact/artifacts/linux.build/*view*/ 
>> .
>>
>> - pre-built clang tarball: 
>> https://ci.linaro.org/view/tcwg-llvm-kernel/job/tcwg-llvm-kernel-bisect-aarch64/9/artifact/artifacts/llvm-install.tar.xz/*view*/ 
>> .
>>
>> - linux kernel version is next-20180830 from linux-next, but I would 
>> expect current linux-next:master fail as well; 
>> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tag/?h=next-20180830
>>
>> [1] 
>> https://ci.linaro.org/view/tcwg-llvm-kernel/job/tcwg-llvm-kernel-bisect-aarch64/9/artifact/artifacts/
>>
>> Thank you,
>>
>> -- 
>> Maxim Kuvyrkov
>> www.linaro.org
>>
>>
>>
>>> On Aug 30, 2018, at 2:22 AM, Philip Reames via llvm-commits 
>>> <llvm-commits at lists.llvm.org> wrote:
>>>
>>> Author: reames
>>> Date: Wed Aug 29 16:22:07 2018
>>> New Revision: 340997
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=340997&view=rev
>>> Log:
>>> [SimplifyCFG] Common debug handling [NFC]
>>>
>>>
>>> Modified:
>>>     llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
>>>
>>> Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
>>> URL: 
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=340997&r1=340996&r2=340997&view=diff
>>> ============================================================================== 
>>>
>>> --- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
>>> +++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Wed Aug 29 
>>> 16:22:07 2018
>>> @@ -2688,8 +2688,6 @@ bool llvm::FoldBranchToCommonDest(Branch
>>>      // all instructions before Cond other than DbgInfoIntrinsic are 
>>> bonus
>>>      // instructions.
>>>      for (auto BonusInst = BB->begin(); Cond != &*BonusInst; 
>>> ++BonusInst) {
>>> -      if (isa<DbgInfoIntrinsic>(BonusInst))
>>> -        continue;
>>>        Instruction *NewBonusInst = BonusInst->clone();
>>>        RemapInstruction(NewBonusInst, VMap,
>>>                         RF_NoModuleLevelChanges | 
>>> RF_IgnoreMissingLocals);
>>> @@ -2816,12 +2814,6 @@ bool llvm::FoldBranchToCommonDest(Branch
>>>
>>>      // TODO: If BB is reachable from all paths through PredBlock, 
>>> then we
>>>      // could replace PBI's branch probabilities with BI's.
>>> -
>>> -    // Copy any debug value intrinsics into the end of PredBlock.
>>> -    for (Instruction &I : *BB)
>>> -      if (isa<DbgInfoIntrinsic>(I))
>>> -        I.clone()->insertBefore(PBI);
>>> -
>>>      return true;
>>>    }
>>>    return false;
>>>
>>>
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