[llvm-dev] [cfe-dev] compiler-rt RFE to support creating profraw for each Shared Library

[Vedant Kumar via llvm-dev]

Hi Oza,

The mechanics of the patch are clear. What's not clear to me is why dso-specific .profraw files are helpful for code coverage, since merged .profraw's should work just as well.

Have you encountered issues using merged .profraws? Could you clarify what's meant by backtracking and instrumenting [the] final binary?

thanks,
vedant

> On Sep 22, 2021, at 9:36 PM, Oza, Hiral <Hiral.Oza at netapp.com> wrote:
> 
> Hello Vedant,
>  
> > could you share some of the use cases for this feature? > What were the pros/cons of any alternatives you considered (e.g. the %m/%c modes)?
>  
> We are taking coverage of shared libraries (i.e. Linux .so) and dumping coverage into files corresponding to SO’s filename.
> With this proposed patch, will get coverage as below for sample code (pls refer compiler-rt/test/profile/Linux/instrprof-shared-nProfraws.test):
> libhi.so  -> will dump into libhi.so.profraw
> libhello.so -> will dump into libhellp.so.profraw
> main.out -> will dump into main.out.profraw
>  
> Regarding ‘%m or %c: (from https://clang.llvm.org/docs/SourceBasedCodeCoverage.html <https://clang.llvm.org/docs/SourceBasedCodeCoverage.html>): %m is expands instrumented binary’s signature (and with “%Nm” dumps into poll of N profraws) and %c seems very different from proposed “%n”.
>  
> Basically with proposed patch (i.e. using “%n”) one can get one-to-one mapping of Shared Library and generated .profraw.
> This makes backtracking and instrumenting final-binary based on feedback easy.
>  
> Please let me know in case of further queries or any changes in proposed patch.
>  
> Thank you.
> -Hiral
>  
> From: cfe-dev <cfe-dev-bounces at lists.llvm.org <mailto:cfe-dev-bounces at lists.llvm.org>> On Behalf Of Oza, Hiral via cfe-dev
> Sent: Wednesday, 22 September, 2021 18:56
> To: cfe-dev at lists.llvm.org <mailto:cfe-dev at lists.llvm.org>; llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>>
> Subject: [cfe-dev] compiler-rt RFE to support creating profraw for each Shared Library
>  
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> 
> 
> 
> Greetings!
>  
> Please review our patch compiler-rt RFE patch here -- https://reviews.llvm.org/D110232 <https://reviews.llvm.org/D110232>
>  
> This patch is about creating profraw for each Shared Library.
>  
> <patch_info>
> SBCC RFE: Support SBCC for Shared Library
>  
> SBCC RFE: Support SBCC for Shared Library
> Using '%n' format parameter for profile name templates, to insert the full
> path of the current shared object into profile file names.
>  
> Internally using a linked list to gather all profile dumping functions
> (there is one defined in each shared object) so they can be invoked with a
> single function call.  Ensure the resulting directory paths are created
> prior to dumping.
> </patch_info>
>  
> Thank you in advance for your kind review.
> -Hiral

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