Fix memory leaks

[boleyn.su]

Summary

For vector<shared_ptr/unique_ptr>'s, emplace_back(new T()) is not
safe and can lead to memory leak. This happens when emplace_back
fails to allocate required memory and throws, and the object allocated
with new will never be deleted. Although this is not an issue
for LLVM as a compiler, it can hurt those who use it as a library.

[boleyn.su]

Hi Chandler Carruth,
I found this bug in your slides at https://llvm.org/devmtg/2014-10/Slides/Carruth-TheLLVMPassManagerPart2.pdf.
I saw the same pattern somewhere else in the llvm repo too but I do not have the time and the tool to fix all of them.
I guess it would be much easier to fix it with the help of LLVM itself.
Hope this helps.
Boleyn Su

[boleyn.su]

Fix a compile error :)

[boleyn.su]

Fix a comiple error again :(

[boleyn.su]

Hi would you mind take a look at the patch?

Sent from https://boleyn.su/phone

[boleyn.su]

Friendly ping.

Sent from https://boleyn.su/phone

[chandlerc]

I don't think LLVM makes any attempt to be exception safe in this way, so not sure how important this is, but sure.

I don't work much on LLVM these days, so @asbirlea or @aeubanks may be better folks to reach out to for fixes here.

[boleyn.su]

Thanks @chandlerc .

@asbirlea and @aeubanks would you mind to take at a look at the CL?

[asbirlea]

Looks good to me as well.
Thought this patch would be good to go with Chandler's accept; for future similar fixes, myself and aeubanks are good contacts.

llvm/include/llvm/IR/PassManager.h

         detail::PassModel<IRUnitT, PassT, PreservedAnalyses, AnalysisManagerT,
                           ExtraArgTs...>;
 
-    Passes.emplace_back(new PassModelT(std::move(Pass)));
+    Passes.emplace_back(std::make_unique<PassModelT>(std::move(Pass)));
   }
 
   /// When adding a pass manager pass that has the same type as this pass