[LLVMdev] LTOModule::parseSymbols not handling GlobalAlias

[Sergei Larin]

Rafael,

  This was triggered by my original question... Can you please take a look? Thanks.

Sergei

> Hi Rafael,
> 
>   I have a quick question for you. First of all I am not very familiar with this
> code, so....
> 
> 
> Before this change:
> 
> [llvm] r212349 - Implement LTOModule on top of IRObjectFile
> http://comments.gmane.org/gmane.comp.compilers.llvm.cvs/195450
> 
> 
> LTOModule::parseSymbols used to explicitly add global aliases as 
> defined
> symbols:
> 
>   // add aliases
>  for (const auto &Alias : IRFile->aliases())
>     addDefinedDataSymbol(Alias);
> 
> After your patch I do not seem to see an explicit handling of 
> aliases... I would
> naively expect something like this:
> 
> for (auto &Sym : IRFile->symbols()) {
> .....
>     if (isa<GlobalVariable>(GV)) {
>       addDefinedDataSymbol(Sym);
>       continue;
>     }
> 
>     if (isa<GlobalAlias>(GV)) {
>       addDefinedDataSymbol(Sym);
>       continue;
>     }
> 
> }
> 
> 
>  Is this an oversight or a design decision? If this is the later, when/where
> aliases should be handled?
> Thanks a lot.
> 
> Sergei
>

---
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> -----Original Message-----
> From: Rafael Espíndola [mailto:rafael.espindola at gmail.com]
> Sent: Tuesday, October 07, 2014 8:01 AM
> To: Shankar Easwaran
> Cc: Sergei Larin; LLVM Developers Mailing List
> Subject: Re: [LLVMdev] LTOModule::parseSymbols not handling GlobalAlias
> 
> On 2 October 2014 12:35, Shankar Easwaran <shankare at codeaurora.org>
> wrote:
> > Hi,
> >
> > There is a genuine case that lto_module_get_num_symbols doesnot
> return
> > all the symbols that are in the bitcode file.
> >
> > Test case:-
> >
> > cat > test.c << \!
> > int bar() { return 0; }
> > int foo()  __attribute__ ((weak, alias ("bar"))); !
> >
> > clang -c test.c -emit-llvm
> >
> > Use a program to list all the symbols using
> > lto_module_get_num_symbols, and foo will be missing from the list.
> 
> I can't reproduce this. If a run
> 
> llvm-lto -dso-symbol bar -dso-symbol foo test.o -o out.o
> 
> I do get both symbols in the output. Setting a breakpoint in
> llvm-lto.cpp:154 also shows NumSyms being 2.
> 
> Cheers,
> Rafael