[cfe-dev] source-to-source transformation to insert instrumentation calls

[Jan Smets]

On 24/09/2012 17:37, Dmitri Gribenko wrote:
> On Sun, Sep 23, 2012 at 8:34 PM, Jan Smets <jan.smets at alcatel-lucent.com> wrote:
>> Hi
>>
>> I'm trying to use CLANG to build a standalone source-to-source
>> transformation tool. My first goal is to insert instrumentation calls for
>> every memory access (wherever possible).
>>
>>
>> For example, from this:
>>
>> int test(int *a)
>> {
>>      int b;
>>      b = 0x10;
>>      *a = b;
>>
>>      if(*a == 0x10)
>>         return 1;
>>      return 0;
>> }
>>
>>
>> To this:
>>
>> int test(int *a )
>> {
>>    int b ;
>>
>>    b = 0x10;
>>    instrument_write(*a, 4);  // 4 is width
>>    *a = b;
>>
>>    instrument_read(*a, 4);
>>    if (*a == 0x10) {
>>      return (1);
>>    }
>>    return (0);
>> }
> Hi Jan,
>
> Just a note: I hope you understand that such source-level
> instrumentation will not be precise.  Optimizations eliminate memory
> accesses.  For example, in this case there will be only one store:
>
> define i32 @test(i32* nocapture %a) nounwind {
>    store i32 16, i32* %a, align 4, !tbaa !0
>    ret i32 1
> }
>
> Dmitri
>
That's OK. I'm aware that I won't be 100% accurate.
Now I just need to figure out a good location to insert the call! :)

Thanks for the feedback.