[PATCH], PR 68404 patch #2 (disable power8/power9 fusion on PowerPC)

David Edelsohn dje.gcc@gmail.com
Fri Feb 12 00:11:00 GMT 2016


On Wed, Feb 10, 2016 at 2:46 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Wed, Feb 10, 2016 at 05:42:17PM -0500, Michael Meissner wrote:
>> This patch disables -mcpu=power8/-mtune=power8 from setting -mpower8-fusion and
>> -mcpu=power9/-mtune=power9 from setting -mpower9-fusion.  I will look at the
>> earlyclobber that Bernd Schmidt mentioned, but for now it may be safest to just
>> disable it for GCC 6.0.
>>
>> I built it on a little endian power8 system, and there were no regressions.  Is
>> it ok to install?
>
> Doesn't this mean the bug is still there, just not enabled unless
> -mpower[89]-fusion (ok, perhaps mitigated by the previous workaround patch)?
> Wouldn't it be better to just forcefully clear the options (and thus ignore
> -them) for the time being if they are known to be broken?
>
>> [gcc]
>> 2016-02-10  Michael Meissner  <meissner@linux.vnet.ibm.com>
>>
>>       PR target/68404
>>       * config/rs6000/predicates.md (fusion_gpr_addis): Revert
>>       2016-02-09 change.
>>
>>       * config/rs6000/rs6000-cpus.def (ISA_2_7_MASKS_SERVER): Do not set
>>       power8/power9 fusion by default.
>>       (ISA_3_0_MASKS_SERVER): Likewise.
>>
>>       * config/rs6000/rs6000.c (rs6000_option_override_internal): Remove
>>       code setting -mpower8-fusion if -mtune=power8 and -mpower9-fusion
>>       if -mtune=power9.
>>
>>       * doc/invoke.texi (RS/6000 and PowerPC Options): Document that
>>       -mpower8-fusion and -mpower9-fusion are not set by default.
>>
>> [gcc/testsuites]
>> 2016-02-10  Michael Meissner  <meissner@linux.vnet.ibm.com>
>>
>>       PR target/68404
>>       * gcc.target/powerpc/fusion.c: Do not assume that -mtune=power8
>>       sets -mpower8-fusion or -mtune=power9 sets -mpower9-fusion.
>>       * gcc.target/powerpc/fusion2.c: Likewise.
>>       * gcc.target/powerpc/fusion3.c: Likewise.

Because of the more recent patches that should fix the cause of this
failure, this set of patches now are moot.

- David



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