On Thu, Aug 20, 2015 at 5:15 PM, Michael Meissner <meiss...@linux.vnet.ibm.com> wrote: > PR 67211 is an error that shows up on the GCC 5.x branch when the test case is > compiled with -mcpu=power7 -mtune=power8 -O3. In looking at the code, I > noticed > that the code optimized adjancent 64-bit integer/pointers in a structure from > DImode to V2DImode. The compiler optimized these to the vector registers, and > then tried to move a common field used later back to the GPR field. If the cpu > was power8, it would be able to use the direct move instructions, but on > power7 > those instructions don't exist. The current trunk compiler has dialed back on > the optimization, and it no longer tries to optimize adjacent fields in this > particular case to V2DImode, but it is an issue in the GCC 5 branch. > > In debugging the issue, I noticed the -mefficient-unaligned-VSX option was > being set if -mtune=power8 was used, even if the architecture was not a > power8. Efficient unaligned VSX is an architecture feature, and not a tuning > feature. In fixing this to be an architecture feature, it no longer tried to > do > the V2DImode optimization because it didn't have fast unaligned support. > > I have checked this on a big endian power7 and a little endian power8 system, > using the GCC 5.x patches and the patches for the trunk. There were no > regressions in any of the runs. Is it ok to install these patches on both the > GCC 5.x branch and trunk? > > I would like to commit a similar patch for the 4.9 branch as well. Is this ok? > > Note, due to rs6000.opt being slightly different between GCC 5.x and trunk, > there are two different patches, one for GCC 5.x and the other for GCC 6.x > (trunk). > > [gcc] > 2015-08-20 Michael Meissner <meiss...@linux.vnet.ibm.com> > > PR target/67211 > * config/rs6000/rs6000-cpus.def (ISA_2_7_MASKS_SERVER): Set > -mefficient-unaligned-vsx on ISA 2.7. > > * config/rs6000/rs6000.opt (-mefficient-unaligned-vsx): Convert > option to a masked option. > > * config/rs6000/rs6000.c (rs6000_option_override_internal): Rework > logic for -mefficient-unaligned-vsx so that it is set via an arch > ISA option, instead of being set if -mtune=power8 is set. Move > -mefficient-unaligned-vsx and -mallow-movmisalign handling to be > near other default option handling. > > [gcc/testsuite] > 2015-08-20 Michael Meissner <meiss...@linux.vnet.ibm.com> > > PR target/67211 > * g++.dg/pr67211.C: New test.
Okay everywhere. Thanks, David
