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Re: [PATCH i386 AVX512] [81/n] Add new built-ins.
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Kirill Yukhin <kirill dot yukhin at gmail dot com>
- Cc: Richard Biener <richard dot guenther at gmail dot com>, Uros Bizjak <ubizjak at gmail dot com>, Richard Henderson <rth at redhat dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 22 Oct 2014 13:40:20 +0200
- Subject: Re: [PATCH i386 AVX512] [81/n] Add new built-ins.
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- References: <20141020134122 dot GB12661 at msticlxl57 dot ims dot intel dot com> <20141020135019 dot GP10376 at tucnak dot redhat dot com> <20141021140805 dot GA22695 at msticlxl57 dot ims dot intel dot com> <20141021142015 dot GY10376 at tucnak dot redhat dot com> <20141021144749 dot GC22695 at msticlxl57 dot ims dot intel dot com> <20141021150826 dot GD22695 at msticlxl57 dot ims dot intel dot com> <CAFiYyc3ubjxjcAwrH-X2=DVP2B5VzL9W2XFpy3wjWtH_O4oLBw at mail dot gmail dot com> <20141022113420 dot GB11644 at msticlxl57 dot ims dot intel dot com>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Wed, Oct 22, 2014 at 03:34:22PM +0400, Kirill Yukhin wrote:
> > Can you test with -mavx512 (or whatever enables the builtins?)
> I did:
> sync && time for i in `seq 1000` ; do ./build-x86_64-linux/gcc/xgcc -B./build-x86_64-linux/gcc -O0 -S test.c -mavx512vl ; done
> Here're results.
> w/o the patch applied:
> real 0m14.245s
> user 0m10.753s
> sys 0m2.150s
> w/ the patch applied:
> real 0m16.404s
> user 0m12.935s
> sys 0m2.577s
> So, we have compilation 15% slowdown when -mavx512vl
> is provided and no difference when not.
> Is this change is acceptable?
As #include <x86intrin.h> enables everything these days,
it will affect also that.
I'd say the 15% slowdown for -mavx512vl and #include <x86intrin.h>
is not something that would preclude applying the patch, but definitely
something to work on later on.
Unfortunately, for the x86intrin.h case, lazy initialization of the builtins
supposedly doesn't help at all, because pretty much all the builtins will be