[LLVMdev] struct type parament

[Mehdi Amini]

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
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>