On 6/17/20 9:00 AM, Shuai Wang wrote:
Dear Martin,
Thanks for the kind reply.
Hey.
You're welcome.
I don't have a strong preference between `asan0` vs. `sanopt`. But I note that
I am primarily working on sanitizer enabled code, where I can only find some
.ASAN_CHECK function calls in `asan0`, but those function calls seem have been
inlined in `sanopt`.
Note that .ASAN_CHECK is not inlined but "instrumented". The function is about
taking look in the shadow memory
and checking that a memory write is valid.
In other words, I can constantly find the following pattern:
*if (_44 != 0)*
goto <bb 9>; [0.05%]
else
goto <bb 8>; [99.95%]
<bb 9> :
__builtin___asan_report_load4 (_34);
The marked if condition is where my analysis and instrumentation starts from.
If I go with `asan0`, then I just cannot find it (it's somewhat wrapped within
.ASAN_CHECK).
Can you please explain which ASAN_CHECKs are you trying to modify? We can
probably find a proper
place where to implement your plugin-in functionality.
Martin
Best,
Shuai
On Wed, Jun 17, 2020 at 2:49 PM Martin Liška <mli...@suse.cz
<mailto:mli...@suse.cz>> wrote:
On 6/17/20 4:10 AM, Shuai Wang via Gcc wrote:
> Hello,
>
> Suppose I have changed certain if condition in the GIMPLE code (generated
> by the `sanopt` pass) into the following format:
Hello.
What kind of instrumentation are you doing? Can you make the instrumentation
in a ASAN pass? Then you'll go through DCE.
Martin
>
> if (0 == 1)
> {
> xxxx
> }
>
> Then, in order to completely remove this unnecessary if condition and the
> guarded true branch, I want to leverage the dead code elimination
> optimization of gcc. However, I just cannot figure out a way of doing
so. I
> use the following command to output the instrumented GIMPLE code:
>
> gcc -fdump-tree-all -fplugin=./instrumentor.so -g -fsanitize=address
test.c
>
> And notice that the instrumented gimple code is right there in the
> outputs: test.c.322t.instrumentor. Everything seems fine.
>
> Anyone could shed some light on how to re-optimize (e.g., with deadcode
> elimination or just use -O3 if possible) the instrumented GIMPLE code?
> Thank you very much.
>
> Shuai
>
