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

[Peter Collingbourne via Phabricator via llvm-commits]

pcc added inline comments.


================
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;
----------------
dmikulin wrote:
> pcc wrote:
> > dmikulin wrote:
> > > davide wrote:
> > > > dmikulin wrote:
> > > > > 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().
> > > > Can you please add a test showing when 3) happens?
> > > 3) is also demonstrated by the test case in the PR. I'm working on regression tests for all known cases and will submit them with the new version of the patch.
> > > _wrap_bar is needed for the case where it is defined by the user but may be eliminated during LTO.
> > 
> > This one only requires `VisibleToRegularObj`, doesn't it?
> Looks like it. Do we want to handle _wrap_* symbols specially and not set the weak binding for LTO?
Up to you. Note that you can make LTO keep a symbol by calling `addUndefined` with the symbol name, so it wouldn't be *that* special.


================
Comment at: lld/ELF/SymbolTable.cpp:124
   for (BitcodeFile *F : BitcodeFiles)
-    LTO->add(*F);
+    LTO->add(*F, isRenamed);
 
----------------
If you move the list of renamed symbols to `Config` you can avoid this lambda.


================
Comment at: lld/ELF/SymbolTable.cpp:192
+  uint8_t Binding = getSymbolBinding(find(Name));
+  RenamedSymbols[Name] = Binding;
+  RenamedSymbols[Name] = Binding;
----------------
You mean `Alias` here, right?


https://reviews.llvm.org/D33621