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

[Dmitri Gribenko]

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

-- 
main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
(j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr at gmail.com>*/