llvm dev - Jan 2019 - option similar to -finstrument-functions but for code blocks

Hi,

I'd like to track not just at the function level, but also at the code
block level. For example, for a if-else statement, I want to know when
the if-branch or else-branch is enter/exit.

Is there a clang option similar to -finstrument-functions for code blocks?

Alternatively, I could manually insert the code to the IR .ll file.

I see the generated .ll use the following function when
-finstrument-functions is enabled. Is there an equivalent function for
code blocks?

%1 = call i8* @llvm.returnaddress(i32 0), !dbg !10

-- 
Regards,
Peng

> On 24 Jan 2019, at 04:13, Peng Yu via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi,
> 
> I'd like to track not just at the function level, but also at the code
> block level. For example, for a if-else statement, I want to know when
> the if-branch or else-branch is enter/exit.
> 
> Is there a clang option similar to -finstrument-functions for code blocks?
> 
> Alternatively, I could manually insert the code to the IR .ll file.
> 
> I see the generated .ll use the following function when
> -finstrument-functions is enabled. Is there an equivalent function for
> code blocks?
> 
> %1 = call i8* @llvm.returnaddress(i32 0), !dbg !10
> 
You’re probably looking for the “coverage” builds of clang which add
instrumentation in the IR:

https://clang.llvm.org/docs/SourceBasedCodeCoverage.html

(Details of the data you can get is at
https://llvm.org/docs/CoverageMappingFormat.html).

I’m not sure there’s something built into LLVM that makes that happen, but I
suggest looking into what the coverage-instrumented .ll files look like when
clang does it.

Cheers

-- Dean

Peng Yu via llvm-dev <llvm-dev at lists.llvm.org> writes:
> I'd like to track not just at the function level, but also at the code
> block level. For example, for a if-else statement, I want to know when
> the if-branch or else-branch is enter/exit.
>
> Is there a clang option similar to -finstrument-functions for code blocks?
Are you looking for code coverage or profile information (block
execution counts)?  Dean already replied with the code coverage
information.  LLVM has a profile instrumentation pass which is run with
opt -profile-generate.  This is gprof-style profiling.  I don't know
offhand which (if any) clang option is hooked up to -profile-generate.

                           -David

On Thu, Jan 24, 2019 at 10:19 AM David Greene <dag at cray.com>
wrote:
>
> Peng Yu via llvm-dev <llvm-dev at lists.llvm.org> writes:
>
> > I'd like to track not just at the function level, but also at the
code
> > block level. For example, for a if-else statement, I want to know when
> > the if-branch or else-branch is enter/exit.
> >
> > Is there a clang option similar to -finstrument-functions for code
blocks?
>
> Are you looking for code coverage or profile information (block
> execution counts)?  Dean already replied with the code coverage
> information.
Not really. I don't care really the number of times an instruction is
called. I care about the control flow and I'd like to visualize it as
a graph. cfg is static. I'd like something dynamic which only shows
what is run.

Of course, having the additional information about the count should be
fine. But it is secondary.
> LLVM has a profile instrumentation pass which is run with
> opt -profile-generate.  This is gprof-style profiling.  I don't know
> offhand which (if any) clang option is hooked up to -profile-generate.
>
>                            -David
-- 
Regards,
Peng