Hi Severin, looks okay to me (not a reviewer however). In our proprietary JVM8 we had set (on Linux) BUILD_LIBFDLIBM_OPTIMIZATION := HIGH and FDLIBM_CFLAGS += -ffp-contract=off for a long time and did not observe any issues . (but we always build with gcc 4.8.x so cannot tell much about lower gcc versions ).
But I really wonder - wouldn’t it be better in the long run to go for a min. gcc versions >= 4.6 (or even 4.8) in OpenJDK8 ? Maybe some people from the distros could comment on this . Best regards, Matthias > -----Original Message----- > From: ppc-aix-port-dev <ppc-aix-port-dev-boun...@openjdk.java.net> On > Behalf Of Severin Gehwolf > Sent: Dienstag, 30. April 2019 13:38 > To: jdk8u-dev <jdk8u-...@openjdk.java.net>; build-dev <build- > d...@openjdk.java.net> > Cc: ppc-aix-port-dev <ppc-aix-port-...@openjdk.java.net> > Subject: [8u] RFR: 8210416: [linux] Poor StrictMath performance due to non- > optimized compilation > > Hi, > > Could I please get a review for this 8u backport related to fdlibm > optimization on Linux? The JDK 12 patch doesn't apply as-is as the JDK > 8 build system is drastically different from JDK 11+. > > Bug: https://bugs.openjdk.java.net/browse/JDK-8210416 > webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK- > 8210416/jdk8/02/ > > The main differences to the original fix are: a) optimization level and > b) additional hook for older GCC. This backport keeps the optimization > level at -O3 (HIGH) over -O2 (LOW) for JDK 8u as this would otherwise > regress Linux ppc64{,le} which currently use -O3. As the current code > has the implicit assumption of ppc64 being compiled on older GCCs too > (JDK-8172053), this backport maintains compatibility in this regard. If > -ffp-contract=off is not available, a machine specific set of flags is > being used if the compiler supports them (-mno-fused-madd -fno-strict- > aliasing). > > For older GCCs (< 4.6) specific machine flags are being used. That is, > for ppc64{,le} and x86{,_64}. ppc64{,le} machine specific flags have > already been determined (See JDK-8172053). x86_64 and x86 have the same > machine specific flags available, so I've used them there too[1]. > > Testing: build/test on gcc 8.x Linux x86_64. build/test on gcc 4.4.7 > x86_64/ppc64. Manual inspection of build logs for fdlibm files (e.g. > w_asin.c). > > Thoughts? > > Thanks, > Severin > > [1] https://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/i386-and-x86_002d64- > Options.html#i386-and-x86_002d64-Options > > > >
