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Re: libsanitizer merge from upstream r208536
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Peter Bergner <bergner at vnet dot ibm dot com>
- Cc: Konstantin Serebryany <konstantin dot s dot serebryany at gmail dot com>, Marek Polacek <polacek at redhat dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Dodji Seketeli <dodji at redhat dot com>, Dmitry Vyukov <dvyukov at google dot com>, "H.J. Lu" <hjl dot tools at gmail dot com>, Yuri Gribov <tetra2005 at gmail dot com>
- Date: Wed, 28 May 2014 00:11:10 +0200
- Subject: Re: libsanitizer merge from upstream r208536
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- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Tue, May 27, 2014 at 05:04:52PM -0500, Peter Bergner wrote:
> On Tue, 2014-05-27 at 23:50 +0200, Jakub Jelinek wrote:
> > On Tue, May 27, 2014 at 04:02:08PM -0500, Peter Bergner wrote:
> > > It's being called form basically two files:
> > >
> > > [bergner@makalu-lp1 gcc-fsf-mainline-asan-debug]$ find . -name '*.o' | xargs nm -AC | grep sync_fetch_and_add_8
> > > ./powerpc64-linux/32/libsanitizer/sanitizer_common/.libs/sanitizer_allocator.o: U __sync_fetch_and_add_8
> > > ./powerpc64-linux/32/libsanitizer/sanitizer_common/sanitizer_allocator.o: U __sync_fetch_and_add_8
> > > ./powerpc64-linux/32/libsanitizer/asan/.libs/asan_allocator2.o: U __sync_fetch_and_add_8
> > > ./powerpc64-linux/32/libsanitizer/asan/asan_allocator2.o: U __sync_fetch_and_add_8
> >
> > Does ppc32 have any atomic 64-bit loads/stores (in the sense that the aligned
> > 64 bits are written as one memory transaction, not each 32-bit word
> > separately)?
>
> The only option I can think of would be using the floating point
> load/store instructions lfd/stfd. Of course if we're going to
> operate on them, then we'd need to copy them back to memory and
> then into the integer registers again....before copying them
> back to the FP registers (thru memory again) so we can store
> them with the stfd.
I think that is pretty much comparable to the use of MMX in i?86 sanitizer.
That will not help on soft-fp ppc, though not sure if anybody with soft-fp
builds libsanitizer.
> > In any case, atomic_uint64_t there seems to be used only for some statistic
> > counter and not really atomic anyway, as additions aren't performed using
> > atomic instructions, but just atomic load, followed by normal arithmetics,
> > followed by atomic store.
> > Can't 32-bit counters be used instead on 32-bit arches?
>
> Using 32-bit counters would be easiest if we can, but Kostya will have
> to answer that.
I agree with that. atomic_uintptr_t would be the type to use I think.
Jakub