[llvm-dev] Dwarf - 5 features in clang and llvm

[Djordje Todorovic via llvm-dev]

Hi Sourabh,

> #include <iostream>
> int func(int* ptr){
>         std::cout << *ptr;
>         return *ptr + 5;
> }
> int main(int argc, char** argv){
>         int a = 4;
>         int* ptr_a = &a;
>         int b = func(ptr_a);
>         return 0;
> }

The 'func()' gets inlined, so according to the DWARF standard the call-site debug info should not be created for calls to inlined functions.

>@Djorde DW_TAG_call_site are supported using late MIR approach, are the new Call Site related development will be supported via MIR. or their will be a frontend level debug metadata support will be added.

The new work is also implemented on the MIR level.

Best,
Djordje

On 11.9.19. 13:07, Sourabh Singh Tomar wrote:
> Hello Djordje, Vedant,
> 
> Thanks a lot for sharing information. 
> 
> I have a doubt, please consider the following simple test case-
> #include <iostream>
> int func(int* ptr){
>         std::cout << *ptr;
>         return *ptr + 5;
> }
> int main(int argc, char** argv){
>         int a = 4;
>         int* ptr_a = &a;
>         int b = func(ptr_a);
>         return 0;
> } 
> commandline used --
> bash$ clang++ -Xclang -femit-debug-entry-values -O2 -ggdb test.cpp
> 
> For this case-- these Tags are not emitted
> DW_TAG_call_site, DW_TAG_call_site_paramter ..
> only DW_AT_GNU_all_call_sites attribute is present.
> 
> + @Djorde DW_TAG_call_site are supported using late MIR approach, are the new Call Site related development will be supported via MIR. or their will be a frontend level debug metadata support will be added.
> 
> Thanks!
> Sourabh.
> 
> 
> 
> On Wed, Sep 11, 2019 at 12:02 PM Djordje Todorovic <djordje.todorovic at rt-rk.com <mailto:djordje.todorovic at rt-rk.com>> wrote:
> 
>     Great to see this! :)
> 
>     Best,
>     Djordje
> 
>     On 10.9.19. 21:16, Vedant Kumar wrote:
>     >
>     >
>     >> On Sep 10, 2019, at 6:15 AM, Djordje Todorovic via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org> <mailto:llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>>> wrote:
>     >>
>     >> Hi Sourabh,
>     >>
>     >> Support for call-site related DWARF 5 tag/attributes is implemented very late, in the LLVM middle-end.
>     >> Please note that there is also the IR-level flag (DIFlagAllCallsDescribed) that lowers to
>     >> the DW_AT_call_all_calls.
>     >>
>     >> There is also support for call-site-parameter (DW_TAG_call_site_parameter) and the debug entry values
>     >> (DW_OP_entry_value) related DWARF 5 symbols, but it is restricted by the CC1 option ‘-femit-debug-entry-values’,
>     >> since the LLDB is still missing support for that.
>     >
>     > Not for too long ;)
>     >
>     > See https://reviews.llvm.org/D67410 & https://reviews.llvm.org/D67376
>     >
>     > best,
>     > vedant
>     >
>     >>
>     >> Best regards,
>     >> Djordje
>     >>
>     >> On 10.9.19. 13:58, Sourabh Singh Tomar via llvm-dev wrote:
>     >>> Hello All,
>     >>>
>     >>> I was working on some dwarf-5 features and debugging optimized code support in clang and llvm. 
>     >>>
>     >>> Noticed that, DW_TAG_call_site is supported in llvm middle-end. but clang is not emitting these. 
>     >>>
>     >>> I was hoping, if someone could provide current status of these features and current status of dwarf-5 features in clang and llvm. 
>     >>> That will be immensely helpful.
>     >>>
>     >>> Thanks!
>     >>> Sourabh.
>     >>>
>     >>> _______________________________________________
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>     >>> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org> <mailto:llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>>
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>     >>>
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>