[LLVMdev] struct type parament

[Mehdi Amini]

Do you really want to map the “source code level” type or does a comparison based on the structural equivalence would be OK?

See:

  /// isLayoutIdentical - Return true if this is layout identical to the
  /// specified struct.
  bool isLayoutIdentical(StructType *Other) const;  


— 
Mehdi

> On Jun 2, 2015, at 2:30 PM, Haopeng Liu <hyliuhp at gmail.com> wrote:
> 
> I tried to compare two types. Because of renaming, the comparison result is not as expected. How to deal with renaming while comparing types?
> 
> Best,
> Haopeng
> 
> On 6/2/15 4:09 PM, Mehdi Amini wrote:
>> Hi Haopeng,
>> 
>> One more element, I just noticed you are using LTO, I am not sure how it is implemented but my guess is that there is a shared LLVMContext. If multiple files include this structure declaration, I wouldn’t be surprised if it trigger creating the type over and over in the IR.
>> 
>> Why is it a problem for you by the way? Does the compilation fails in some way?
>> 
>> —
>> Mehdi
>> 
>>> On Jun 2, 2015, at 1:31 PM, Haopeng Liu <hyliuhp at gmail.com> wrote:
>>> 
>>> Hi Mehdi,
>>> 
>>> Thanks for your reply.
>>> 
>>> It seems caused by random rename because I saw %struct.StructTyName.692.475*, which might be twice renaming.
>>> 
>>> Does this collision occur because this type is declared more than once?
>>> 
>>> I encountered this problem when used clang to compile transmission 1.42 (http://download.transmissionbt.com/files/) with configuration: "./configure --disable-gtk". Then in ./third-party/libevent/event.o.ll, you can see the function "event_base_get_method" is an example.
>>> 
>>> Best,
>>> Haopeng
>>> 
>>> On 6/2/15 1:48 PM, Mehdi Amini wrote:
>>>> Hi,
>>>> 
>>>> I think this is when a collision is found on the name.
>>>> I would be interesting to have the full test, it might be that the API is used in a way such that type is constantly re-created even if it already exists, which might be inefficient.
>>>> 
>>>> See in lib/IR/Type.cpp, StructType::setName(StringRef Name):
>>>> 
>>>> ...
>>>>   // While we have a name collision, try a random rename.
>>>>   if (Entry->getValue()) {
>>>>     SmallString<64> TempStr(Name);
>>>>     TempStr.push_back('.');
>>>>     raw_svector_ostream TmpStream(TempStr);
>>>>     unsigned NameSize = Name.size();
>>>>         do {
>>>>       TempStr.resize(NameSize + 1);
>>>>       TmpStream.resync();
>>>>       TmpStream << getContext().pImpl->NamedStructTypesUniqueID++;
>>>>              Entry = &getContext().pImpl->
>>>>                  NamedStructTypes.GetOrCreateValue(TmpStream.str());
>>>>     } while (Entry->getValue());
>>>>   }
>>>> 
>>>> 
>>>> —
>>>> Mehdi
>>>> 
>>>>> On Jun 2, 2015, at 11:23 AM, Haopeng Liu <hyliuhp at gmail.com> wrote:
>>>>> 
>>>>> Hi All,
>>>>> 
>>>>> I generated the following code with "clang -flto" command.
>>>>> 
>>>>> void test(struct StruTyName *a) {
>>>>>    ...
>>>>> }
>>>>> 
>>>>> Then the type of test function is "void (%struct.StruTyName.100*)" by calling function::getFunctionType API.
>>>>> 
>>>>> What's the meaning of number 100?
>>>>> 
>>>>> Best,
>>>>> Haopeng
>>>>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
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>