On 15/08/14 01:24 PM, Jason Evans wrote: > On Aug 6, 2014, at 6:34 AM, Ingvar Hagelund <ing...@redpill-linpro.com> wrote: >>> Ingvar Hagelund wrote >>>> jemalloc-3.6.0 fails to build on to-be-fedora-21 >>>> >>>> https://kojipkgs.fedoraproject.org//work/tasks/2036/7002036/build.log >>>> >>>> Seems like gcc-4.9.0 changed emmintrin.h >>> >>> ... though only when compiling against Fedora's i686 target, that is >>> "gcc -m32 -march=i686 -mtune=atom" >>> >>> x86_64 and the generic i386 target, that is "gcc -march=i386 >>> -mtune=generic" , works fine (though generic i386 is not a primary >>> Fedora target anymore). >> >> >> This is because of github commit >> cb657e3170349a27e753cdf6316513f56550205e >> >> See also jemalloc github issue 52: >> >> https://github.com/jemalloc/jemalloc/issues/52 >> >> Adding -msse2 to CFLAGS fixes the build on Fedora, but there is an issue >> with this: Fedora supports the i686 arch. i686 predates SSE2. i686 means >> PentiumPro and above, while SSE2 was included around Pentium II, that is >> later. So there is no guaranteed support for SSE2 in Fedora. >> >> Grepping through the code, it looks like SSE2 is only used for test >> cases. Does jemalloc use SSE2 features at runtime? If it does, will it >> work correctly without SSE2 available? > > jemalloc doesn’t explicitly use SSE2; it’s for test code only. If I’d known > how much portability trouble the SSE2 optimizations for the Merseinne Twister > PRNG would cause, I’d have left them completely disabled. Maybe it’s time to > give up on SSE2, since nothing important depends on it. > > Jason
If performance is critical, perhaps a much simpler XorShift RNG would be a better choice. They're blazing fast and the quality is more than good enough for fuzzing. http://xorshift.di.unimi.it/
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