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Re: [RFC] PR64703, glibc sysdeps/powerpc/powerpc64/dl-machine.h miscompile
- From: Alan Modra <amodra at gmail dot com>
- To: Jakub Jelinek <jakub at redhat dot com>
- Cc: Richard Biener <richard dot guenther at gmail dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Fri, 30 Jan 2015 12:02:29 +1030
- Subject: Re: [RFC] PR64703, glibc sysdeps/powerpc/powerpc64/dl-machine.h miscompile
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- References: <20150123232339 dot GS12931 at bubble dot grove dot modra dot org> <CAFiYyc1YFTYb3uEE10pU03=hycOALXiyPJeNPOA6OqKOE2Cf-g at mail dot gmail dot com> <20150127123323 dot GU12931 at bubble dot grove dot modra dot org> <20150129141437 dot GA14796 at bubble dot grove dot modra dot org> <CAFiYyc0QHSetUYiNDsv8WR-rcYjst7d98jCN_pHtTGFds1fwZQ at mail dot gmail dot com> <CAFiYyc1meNf4q=geOxeBqS0c6v1jT2t5-rNG-dE5Lu+Dmasa4A at mail dot gmail dot com> <CAFiYyc2uFxKyToseh2kFE50QqRFQgMVtgLrR3-TJVym3T0Jhxg at mail dot gmail dot com> <20150129155147 dot GL1746 at tucnak dot redhat dot com>
On Thu, Jan 29, 2015 at 04:51:47PM +0100, Jakub Jelinek wrote:
> Won't the patch pessimize say const method calls through vtable?
I was worried about accidental pessimization too, so ran a full gcc
build with the patch and compared against one with s/ABI_AIX/ABI_NONE/
in rs6000_has_function_descriptors.
$ for z in `find . -name testsuite -prune -o -name \*.o -print`; do cmp -s $z ~/build/gcc64-current.save/$z || echo $z >> files; done
That showed up a whole lot of libjava differences which on inspection
proved to be .debug_str ordering. Ick. OK, let's look at just code
differences. (BTW, testsuite pruned because "make check" was still
running.)
$ for z in `cat files`; do objdump -d $z | tail -n +5 > dump; objdump -d ~/build/gcc64-current.save/$z | tail -n +5 > dump2; cmp -s dump dump2 || echo $z >> files2; done
$ cat files2
./gcc/rs6000.o
./prev-gcc/rs6000.o
./stage1-gcc/rs6000.o
So the patch didn't make a real mess..
--
Alan Modra
Australia Development Lab, IBM