[llvm] r254348 - Replace all weight-based interfaces in MBB with probability-based interfaces, and update all uses of old interfaces.

[Hans Wennborg via llvm-commits]

Sounds good. I'll keep an eye on the Chromium bots.

Thanks,
Hans

On Mon, Nov 30, 2015 at 5:00 PM, Cong Hou <congh at google.com> wrote:
> The patch is submitted as r254356. As I didn't get this failure
> locally, let's see if this can fix all issues caused by the original
> patch. Otherwise I will revert the revision.
>
>
> thanks,
> Cong
>
>
> On Mon, Nov 30, 2015 at 4:56 PM, Cong Hou <congh at google.com> wrote:
>> I have also noticed several buildbot failures. I have found the cause
>> and now testing the patch below:
>>
>>
>> diff --git a/lib/CodeGen/MachineBlockPlacement.cpp
>> b/lib/CodeGen/MachineBlockPlacement.cpp
>> index ddddd48..fcddf34 100644
>> --- a/lib/CodeGen/MachineBlockPlacement.cpp
>> +++ b/lib/CodeGen/MachineBlockPlacement.cpp
>> @@ -423,9 +423,13 @@
>> MachineBlockPlacement::selectBestSuccessor(MachineBasicBlock *BB,
>>
>>    DEBUG(dbgs() << "Attempting merge from: " << getBlockName(BB) << "\n");
>>    for (MachineBasicBlock *Succ : Successors) {
>> -    BranchProbability SuccProb(
>> -        MBPI->getEdgeProbability(BB, Succ).getNumerator(),
>> -        AdjustedSumProb.getNumerator());
>> +    BranchProbability SuccProb;
>> +    uint32_t SuccProbN = MBPI->getEdgeProbability(BB, Succ).getNumerator();
>> +    uint32_t SuccProbD = AdjustedSumProb.getNumerator();
>> +    if (SuccProbN >= SuccProbD)
>> +      SuccProb = BranchProbability::getOne();
>> +    else
>> +      SuccProb = BranchProbability(SuccProbN, SuccProbD);
>>
>>      // If we outline optional branches, look whether Succ is unavoidable, i.e.
>>      // dominates all terminators of the MachineFunction. If it does, other
>>
>>
>> Thank you for reporting this!
>>
>>
>> thanks,
>> Cong
>>
>>
>> On Mon, Nov 30, 2015 at 4:51 PM, Hans Wennborg <hans at chromium.org> wrote:
>>> On Mon, Nov 30, 2015 at 4:02 PM, Cong Hou via llvm-commits
>>> <llvm-commits at lists.llvm.org> wrote:
>>>> Author: conghou
>>>> Date: Mon Nov 30 18:02:51 2015
>>>> New Revision: 254348
>>>>
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=254348&view=rev
>>>> Log:
>>>> Replace all weight-based interfaces in MBB with probability-based interfaces, and update all uses of old interfaces.
>>>
>>> [...]
>>>
>>>> @@ -43,6 +46,19 @@ BranchProbability::BranchProbability(uin
>>>>    }
>>>>  }
>>>>
>>>> +BranchProbability
>>>> +BranchProbability::getBranchProbability(uint64_t Numerator,
>>>> +                                        uint64_t Denominator) {
>>>> +  assert(Numerator <= Denominator && "Probability cannot be bigger than 1!");
>>>
>>> We hit this assert pretty early in a Chromium build:
>>>
>>> http://build.chromium.org/p/chromium.fyi/builders/ClangToTWin/builds/5080/steps/compile/logs/stdio
>>>
>>> I'll see if I can extract a reproducer.