[PATCH] D33621: Fix for -wrap linker option and LTO, PR 33145

[Dmitry Mikulin via Phabricator via llvm-commits]

dmikulin added inline comments.


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Comment at: lld/ELF/SymbolTable.cpp:159-163
+  Twine WrappedName = "__wrap_" + Name;
+  Twine RealName = "__real_" + Name;
+  RenamedSymbols[WrappedName.str()] = true;
+  RenamedSymbols[RealName.str()] = true;
+  RenamedSymbols[Name] = true;
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davide wrote:
> Can you explain why you need all three?
We need all three if we want to match non-LTO behavior. 
*  _wrap_bar is needed for the case where it is defined by the user but may be eliminated during LTO. 
*  _real_bar is needed for the test case in the PR: the direct call to _real_bar() from foo() will be bound and inlined by LTO to the user-defined _real_bar() instead of bar() if _real_bar() is not on the list.
*  similarly, if bar() is not on the list, the call to bar() from foo() will be inlined instead of being routed to _wrap_bar().


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Comment at: lld/ELF/SymbolTable.cpp:338-340
+      if ((postLTO && B->isBitcode()) &&
+          Binding == STB_WEAK && S->Binding != STB_WEAK)
+        ;
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davide wrote:
> empty ifs are not really common in llvm.
I'll fix this. Negating the condition seamed counter-intuitive...


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Comment at: lld/ELF/SymbolTable.h:140
   std::unique_ptr<BitcodeCompiler> LTO;
+  llvm::StringMap<bool> RenamedSymbols;
+  bool PostLTO = false;
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davide wrote:
> A `StringMap<bool>` is a little silly.
> If you really want a set container, you should use a proper one.
Is a set container like SmallSet good enough in this case? What's the worst case for the number of -wrap functions? I picked a map because we have to do a lookup in this container for every symbol.


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Comment at: llvm/include/llvm/LTO/LTO.h:385
+  /// option.
+  unsigned IsRenamed : 1;
 };
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davide wrote:
> I'd say, `LinkerRedefined`.
I'll change this.


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Comment at: llvm/lib/LTO/LTO.cpp:423
        Partition == GlobalResolution::RegularLTO);
+  GlobalRes.IsRenamed = Res.IsRenamed;
 }
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davide wrote:
> why do you need this being part of GlobalResolution?
> If you do, please add a test showing that you fail switching the linkage earlier.
You're right, I can do it sooner, in addRegularLTO(). I'll take out the GlobalRes stuff.


https://reviews.llvm.org/D33621