On Tue, Dec 27, 2016 at 11:30 PM, David Holmes <david.hol...@oracle.com> wrote: > Hi Volker, > > As this is a build change I have added build-dev. > > The change looks fine to me. >
Thanks for reviewing! > Aside: More generally it would be nice if there was a simple way to record > minimum compiler versions necessary for a given flag/option. > Yes, I first wanted to do this compiler-version dependent. Unfortunately that would have been much more complex because I don't have access to the compiler version in CoreLibraries.gmk and I didn't wanted to start it for legacy code which is not needed in jdk9 anyway. Regards, Volker > Thanks, > David > > > On 28/12/2016 3:17 AM, Volker Simonis wrote: >> >> Hi, >> >> can I please have a review and approval for pushing the following >> small, ppc64-only fix to jdk8u-dev: >> >> http://cr.openjdk.java.net/~simonis/webrevs/2016/8172053/ >> https://bugs.openjdk.java.net/browse/JDK-8172053 >> >> The problem is that the recent downport of "8170153: >> PPC64/s390x/aarch64: Poor StrictMath performance due to non-optimized >> compilation" breaks the build of jdk8u with the original gcc 4.3 on >> linux/ppc64. We should however ensure, that an update-release will not >> break the original tool chain used for a released version of Java. >> Notice, that this change won't go to jdk9 because it only fixes an >> issue caused by the downport of another fix to jdk8u which doesn't >> exist in jdk9. >> >> JDK-8170153 increased the optimization level for the compilation of >> fdlibm on both linux/ppc64 and linux/ppc64le. This only worked by >> using the option '-ffp-contract=off' which guaranteed correct IEEE >> floating point behavior. >> >> Unfortunately, '-ffp-contract' is only available since gcc 4.6. For >> ppc64le that's no problem since ppc64le support only appeared in gcc >> 4.8.3. But on ppc64 (big endian) we traditionally compiled with gcc >> 4.3 which only knows '-mno-fused-madd'. However, that's still not >> enough to get the float computations right - we additionally have to >> supply '-fno-strict-aliasing'. >> >> I've tested the new configuration (i.e. '-mno-fused-madd >> -fno-strict-aliasing') with the corresponding jtreg and JCK tests and >> couldn't find any issue. >> >> Thank you and best regards, >> Volker >> >
