llvm dev - Oct 2014 - [LLVMdev] LTOModule::parseSymbols not handling GlobalAlias

Hello everyone,

  ...I should have used a different subject line in the first place...


I've asked Rafael a question about GlobalAlias handling in
LTOModule::parseSymbols, but he seems to be on vacation...


Does anyone knows the answer?

Thanks a lot!

Sergei


---
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by
The Linux Foundation

> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at
cs.uiuc.edu]
> On Behalf Of Sergei Larin
> Sent: Thursday, October 02, 2014 11:06 AM
> To: 'Rafael Espíndola'
> Cc: 'LLVM Developers Mailing List'
> Subject: Re: [LLVMdev] [RFC] Exhaustive bitcode compatibility tests for IR
> features
> 
> 
> 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
> 
> 
> 
> 
> ---
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> hosted by The Linux Foundation
> 
> 
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

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.

Thanks

Shankar Easwaran

On 10/2/2014 11:22 AM, Sergei Larin wrote:
> Hello everyone,
>
>    ...I should have used a different subject line in the first place...
>
>
> I've asked Rafael a question about GlobalAlias handling in
> LTOModule::parseSymbols, but he seems to be on vacation...
>
>
> Does anyone knows the answer?
>
> Thanks a lot!
>
> Sergei
>
>
> ---
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
by
> The Linux Foundation
>
>
>> -----Original Message-----
>> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at
cs.uiuc.edu]
>> On Behalf Of Sergei Larin
>> Sent: Thursday, October 02, 2014 11:06 AM
>> To: 'Rafael Espíndola'
>> Cc: 'LLVM Developers Mailing List'
>> Subject: Re: [LLVMdev] [RFC] Exhaustive bitcode compatibility tests for
IR
>> features
>>
>>
>> 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
>>
>>
>>
>>
>> ---
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>> hosted by The Linux Foundation
>>
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the
Linux Foundation

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