On Thu, Apr 17, 2014 at 4:56 PM, Yuri Gribov <[email protected]> wrote:

> >> > btw, I've run SPEC (test data, C only) and it shows that out-of-line
> >> > instrumentation is 2x slower.
> >>
> >> I wonder whether this is due to PLT redirection.
> >
> > clang uses static asan-rt by default, no PLT.
>
> Agreed, this will only matter for sanitized shared libraries.
>
> I wonder where such big difference is coming from. I'll examine perf
> when I finally get my hands on SPEC2006.
>
You don't need SPEC,  just run something small like bzip2.

regular asan instrumentation requires 1 load.
a call, which itself does 1 load, costs two more loads (call and ret),
besides the call puts more pressure on the reg allocator which causes more
spills.

--kcc





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