RFR: 8210416: [linux] Poor StrictMath performance due to non-optimized compilation
Severin Gehwolf
sgehwolf at redhat.com
Thu Sep 6 10:12:22 UTC 2018
Hi David,
On Thu, 2018-09-06 at 07:32 +1000, David Holmes wrote:
> Hi Severin,
>
> Might as well raise this here too as it's really a build philosophy
> issue. Shouldn't flags like -ffp-contract=off (and the existing AIX
> -qfloat=nomaf) be toolchain specific rather than platform specific?
Looks like Clang has -ffp-contract:
https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-ffp-contract
Is there any other (supported) toolchain other than gcc and clang on
linux? As for AIX I suppose there is only on supported toolchain?
Thanks,
Severin
> Thanks,
> David
>
> On 5/09/2018 11:12 PM, Severin Gehwolf wrote:
> > Hi,
> >
> > Cross-posting this review-thread on core-libs-dev and build-dev as
> > this
> > is a build change, but affects fdlibm which is core-libs.
> >
> > With JDK-8170153 optimization for fdlibm code has been turned on
> > for
> > ppc64 s390 and aarch64. This patch intends to turn it on on all
> > arches
> > on Linux. I've not observed any precision issues. Is there a good
> > reason to not use -O3 -ffp-contract=off everywhere?
> >
> > Bug: https://bugs.openjdk.java.net/browse/JDK-8210416
> > webrev:
> > http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8210416/webrev.01/
> >
> > Testing: - java/lang/Math, java/lang/StrictMath tests (all pass).
> > - Currently running through submit repo.
> >
> > A simple micro benchmark from JDK-8170153[1] shows these numbers
> > for
> > StrictMath:
> >
> > Function | before | after
> > ----------------------------------------------
> > sin | 0m33.382s | 0m18.731s
> > cos | 0m31.562s | 0m18.796s
> > tan | 0m33.657s | 0m21.093s
> > atan | 0m5.714s | 0m4.902s
> > log | 0m6.212s | 0m4.439s
> > log10 | 0m7.946s | 0m5.543s
> > sqrt | 0m0.481s | 0m0.449s
> > cbrt | 0m5.295s | 0m5.214s
> > tanh | 0m1.404s | 0m1.307s
> > log1p | 0m6.457s | 0m5.131s
> > IEEEremainder | 0m10.629s | 0m6.048s
> > atan2 | 0m8.037s | 0m5.668s
> > hypot | 0m2.171s | 0m2.147s
> >
> > Thoughts?
> >
> > Thanks,
> > Severin
> >
> >
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