llvm dev - Oct 2016 - Basic block execution over time

Hello All,

How can I keep track of the different basic blocks of a program executed over
time?
Or in other words, how can I annotate the block name (block_a) and the
time/cycle at which that blocs (block_a) was executed, and do this for all the
blocks on a reasonable simple program?

Regards, Raul.
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Hi,

I believe the easiest way to do this is using the new `trace_pc`
functionality from SanitizerCoverage. See
http://clang.llvm.org/docs/SanitizerCoverage.html#tracing-pcs for some
documentation about that.

In short:

- Compile your program with the `-fsanitize-coverage=trace-pc` flag.
- This adds a call to a function called `__sanitizer_cov_trace_pc` to every
edge in the control-flow graph.
- You can define this function in any way you want (just write C code, and
link it to the application)
- In particular, you can use `__builtin_return_address` to find where the
function was called from. You're then free to dump that address to a file
descriptor, store it in a memory buffer, ...

Cheers,
Jonas

On Fri, Oct 28, 2016 at 5:20 PM Raul Garcia via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hello All,
>
> How can I keep track of the different basic blocks of a program executed
> over time?
> Or in other words, how can I annotate the block name (block_a) and the
> time/cycle at which that blocs (block_a) was executed, and do this for all
> the blocks on a reasonable simple program?
>
> Regards, Raul.
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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The other option might be to see whether you could use XRay, but that might not
give you basic blocks (though it will give you cycle time, thread, and function
entry/exit points). The tooling for analysing the XRay trace files is under
development and we're still lacking documentation -- but if you're
interested I'd be happy to describe how to use it.

Cheers

-- Dean
> On 29 Oct. 2016, at 23:29, Jonas Wagner via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi,
> 
> I believe the easiest way to do this is using the new `trace_pc`
functionality from SanitizerCoverage. See
http://clang.llvm.org/docs/SanitizerCoverage.html#tracing-pcs for some
documentation about that.
> 
> In short:
> 
> - Compile your program with the `-fsanitize-coverage=trace-pc` flag.
> - This adds a call to a function called `__sanitizer_cov_trace_pc` to every
edge in the control-flow graph.
> - You can define this function in any way you want (just write C code, and
link it to the application)
> - In particular, you can use `__builtin_return_address` to find where the
function was called from. You're then free to dump that address to a file
descriptor, store it in a memory buffer, ...
> 
> Cheers,
> Jonas
> 
> On Fri, Oct 28, 2016 at 5:20 PM Raul Garcia via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> Hello All, 
> 
> How can I keep track of the different basic blocks of a program executed
over time?
> Or in other words, how can I annotate the block name (block_a) and the
time/cycle at which that blocs (block_a) was executed, and do this for all the
blocks on a reasonable simple program?
> 
> Regards, Raul.    
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev