[llvm] r269635 - ThinLTO: fix another non-determinism in bitcode writing

[Mehdi Amini via llvm-commits]

> On May 16, 2016, at 1:41 PM, Duncan P. N. Exon Smith <dexonsmith at apple.com> wrote:
> 
>> 
>> On 2016-May-16, at 01:50, Mehdi Amini via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>> 
>> Author: mehdi_amini
>> Date: Mon May 16 03:50:27 2016
>> New Revision: 269635
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=269635&view=rev
>> Log:
>> ThinLTO: fix another non-determinism in bitcode writing
>> 
>> GlobalVars Refs are initialized from a DenseSet. We can sort them
>> using the value id to recover some determinism during serialization.
>> 
>> From: Mehdi Amini <mehdi.amini at apple.com>
>> 
>> Modified:
>>   llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp
>> 
>> Modified: llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp?rev=269635&r1=269634&r2=269635&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp (original)
>> +++ llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp Mon May 16 03:50:27 2016
>> @@ -3213,8 +3213,15 @@ void ModuleBitcodeWriter::writeModuleLev
>>  NameVals.push_back(getEncodedGVSummaryFlags(V));
>>  auto *Summary = Index->getGlobalValueSummary(V);
>>  GlobalVarSummary *VS = cast<GlobalVarSummary>(Summary);
>> -  for (auto Ref : VS->refs())
>> -    NameVals.push_back(VE.getValueID(Ref.getValue()));
>> +
>> +  // Compute refs in a separate vector to be able to sort them for determinism.
>> +  std::vector<uint64_t> Refs;
>> +  Refs.reserve(VS->refs().size());
>> +  for (auto &RI : VS->refs())
>> +    Refs.push_back(VE.getValueID(RI.getValue()));
>> +  std::sort(Refs.begin(), Refs.end());
>> +  NameVals.insert(NameVals.end(), Refs.begin(), Refs.end());
> 
> Same comment as r269634: there's no need for an auxiliary std::vector here.

Thanks, r269715 for both.

-- 
Mehdi


> 
>> +
>>  Stream.EmitRecord(bitc::FS_PERMODULE_GLOBALVAR_INIT_REFS, NameVals,
>>                    FSModRefsAbbrev);
>>  NameVals.clear();
>> 
>> 
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