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Re: [PATCH 4/4] Un-XFAIL ssa-dom-cse-2.c for most platforms
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Alan Lawrence <alan dot lawrence at foss dot arm dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, Bill Schmidt <wschmidt at linux dot vnet dot ibm dot com>
- Date: Fri, 15 Jan 2016 11:50:37 +0100
- Subject: Re: [PATCH 4/4] Un-XFAIL ssa-dom-cse-2.c for most platforms
- Authentication-results: sourceware.org; auth=none
- References: <1450703608-8617-1-git-send-email-alan dot lawrence at arm dot com> <1450703608-8617-5-git-send-email-alan dot lawrence at arm dot com> <CAGWvnymtU9WWv7tYmcHYn98OPah773j4WyHbKDwJ+GQ+db3Jhg at mail dot gmail dot com> <1450709954 dot 8329 dot 67 dot camel at gnopaine> <5678191B dot 4030608 at foss dot arm dot com> <gcc-patches at gcc dot gnu dot org> <1450712016 dot 8329 dot 72 dot camel at gnopaine> <5698CDFB dot 3080301 at foss dot arm dot com>
On Fri, Jan 15, 2016 at 11:46 AM, Alan Lawrence
<alan.lawrence@foss.arm.com> wrote:
> It seems the conclusion on PowerPC is to XFAIL the test on powerpc64 (there
> will be XPASSes with -mcpu=power7 or -mcpu=power8). Which is what the
> original patch does
> (https://gcc.gnu.org/ml/gcc-patches/2015-12/msg01979.html). So,
>
> Ping.
Ok.
Richard.
> Thanks, Alan
>
> On 21/12/15 15:33, Bill Schmidt wrote:
>>
>> On Mon, 2015-12-21 at 15:22 +0000, Alan Lawrence wrote:
>>>
>>> On 21/12/15 14:59, Bill Schmidt wrote:
>>>>>>
>>>>>>
>>>>>> On powerpc64, the test passes with -mcpu=power8 (the loop is
>>>>>> vectorized as a
>>>>>> reduction); however, without that, similar code is generated to Alpha
>>>>>> (the
>>>>>> vectorizer decides the reduction is not worthwhile without SIMD
>>>>>> support), and
>>>>>> the test fails; hence, I've XFAILed for powerpc, but I think I could
>>>>>> condition
>>>>>> the XFAIL on powerpc64 && !check_p8vector_hw_available, if preferred?
>>>>>
>>>>>
>>>>> Fun.
>>>>>
>>>>> Does it work with -mcpu=power7?
>>>
>>>
>>> Yes, it works with -mcpu=power7, as well as -mcpu=power8, but not e.g.
>>> -mcpu=power6.
>>>
>>>>> Bill: What GCC DejaGNU incantation would you like to see?
>>>>
>>>>
>>>> This sounds like more fallout from unaligned accesses being faster on
>>>> POWER8 than previous hardware. What about conditioning the XFAIL on
>>>>
>>>> { powerpc*-*-* && { ! vect_hw_misalign } }
>>>>
>>>> -- does this work properly?
>>>
>>>
>>> Not on a stage1 compiler - check_p8vector_hw_available itself requires
>>> being
>>> able to run executables - I'll check on gcc112. However, both look like
>>> they're
>>> really about the host (ability to execute an asm instruction), not the
>>> target
>>> (/ability for gcc to output such an instruction)....
>>
>>
>> Hm, that looks like a pervasive problem for powerpc. There are a number
>> of things that are supposed to be testing effective target but rely on
>> check_p8vector_hw_available, which as you note requires executing an
>> instruction and is really about the host. We need to clean that up; I
>> should probably open a bug. Kind of amazed this has gotten past us for
>> a couple of years.
>>
>> For now, just XFAILing for powerpc seems the best alternative for this
>> test.
>>
>> Thanks,
>> Bill
>>
>>>
>>> --Alan
>>>
>>
>>
>