llvm dev - May 2017 - [GlobalISel][AArch64] Toward flipping the switch for O0: Please give it a try!

Hi,

I ran into a little snag on the test-suite:
https://bugs.llvm.org/show_bug.cgi?id=33021
It boils down to GlobalISel generating calls to fabs instead of using
FABSDr (so we get undefined references).

Cheers,
Diana

On 11 May 2017 at 18:40, Quentin Colombet <qcolombet at apple.com>
wrote:
> Hi Diana,
>
> Thanks for the summary.
>
> On May 11, 2017, at 4:01 AM, Diana Picus <diana.picus at linaro.org>
wrote:
>
> Hi all,
>
> I'm still running some validation on this, I'll send an email when
> it's done. If that goes well I don't have anything against making
the
> switch.
>
> For the record, here's a summary of issues that were deferred for
> later on (some of which are optimization-ish and we might decide to
> never do at -O0 at all):
> * Crash in RegBankSelect for half fp types:
> https://bugs.llvm.org/show_bug.cgi?id=32560
>
>
> I’ll have a look.
>
> * Improving constant placement: http://bugs.llvm.org/show_bug.cgi?id=32561
>
>
> I’ve commented in the PR to mention the localizer technic I was playing
> with, if someone wants to give it a try.
>
> * Fancy switch lowering
> * Transforming division-by-constant-power-of-2 into right shift
>
>
> AFAICT all the other issues that were brought up were fixed (yay!).
>
> Cheers,
> Diana
>
>
> Cheers,
> -Quentin
>
>
>
> On 11 May 2017 at 08:44, Kristof Beyls via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>
>
> On 10 May 2017, at 17:36, Quentin Colombet <qcolombet at apple.com>
wrote:
>
>
> MultiSource/Benchmarks/mediabench/mpeg2/mpeg2dec/mpeg2decode (46%):
Function
> Reference_IDCT: Probably due to creating all constants in the entry BB +
> spilling floating point data through an X register:
>
> FastISel:
> fadd d0, d1, d0
> str d0, [sp,#528]
> GlobalISel:
> fadd d0, d1, d0
> fmov x9, d0
> stur x9, [x29,#-48]
>
>
> Good finding, I forgot to do stores in my previous fix. I’ll do them
> shortly.
>
>
> Should be fixed by r302679
>
>
> Thanks Quentin,
>
> That reduces the slow-down when enabling globalisel at -O0 from 13% (on
> r302453)  to 9.5% (on r302679) in my experiments.
> The code size increase also reduces from just over 3% to 2.8%.
>
> Kristof
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>

It turns out that can be fixed by adding -lm to the link line, so I
will probably convert it into a test-suite bug.

I don't suppose it's crucial to handle the fabs intrinsic nicely at -O0.

On 12 May 2017 at 13:44, Diana Picus <diana.picus at linaro.org>
wrote:
> Hi,
>
> I ran into a little snag on the test-suite:
> https://bugs.llvm.org/show_bug.cgi?id=33021
> It boils down to GlobalISel generating calls to fabs instead of using
> FABSDr (so we get undefined references).
>
> Cheers,
> Diana
>
> On 11 May 2017 at 18:40, Quentin Colombet <qcolombet at apple.com>
wrote:
>> Hi Diana,
>>
>> Thanks for the summary.
>>
>> On May 11, 2017, at 4:01 AM, Diana Picus <diana.picus at
linaro.org> wrote:
>>
>> Hi all,
>>
>> I'm still running some validation on this, I'll send an email
when
>> it's done. If that goes well I don't have anything against
making the
>> switch.
>>
>> For the record, here's a summary of issues that were deferred for
>> later on (some of which are optimization-ish and we might decide to
>> never do at -O0 at all):
>> * Crash in RegBankSelect for half fp types:
>> https://bugs.llvm.org/show_bug.cgi?id=32560
>>
>>
>> I’ll have a look.
>>
>> * Improving constant placement:
http://bugs.llvm.org/show_bug.cgi?id=32561
>>
>>
>> I’ve commented in the PR to mention the localizer technic I was playing
>> with, if someone wants to give it a try.
>>
>> * Fancy switch lowering
>> * Transforming division-by-constant-power-of-2 into right shift
>>
>>
>> AFAICT all the other issues that were brought up were fixed (yay!).
>>
>> Cheers,
>> Diana
>>
>>
>> Cheers,
>> -Quentin
>>
>>
>>
>> On 11 May 2017 at 08:44, Kristof Beyls via llvm-dev
>> <llvm-dev at lists.llvm.org> wrote:
>>
>>
>> On 10 May 2017, at 17:36, Quentin Colombet <qcolombet at
apple.com> wrote:
>>
>>
>> MultiSource/Benchmarks/mediabench/mpeg2/mpeg2dec/mpeg2decode (46%):
Function
>> Reference_IDCT: Probably due to creating all constants in the entry BB
+
>> spilling floating point data through an X register:
>>
>> FastISel:
>> fadd d0, d1, d0
>> str d0, [sp,#528]
>> GlobalISel:
>> fadd d0, d1, d0
>> fmov x9, d0
>> stur x9, [x29,#-48]
>>
>>
>> Good finding, I forgot to do stores in my previous fix. I’ll do them
>> shortly.
>>
>>
>> Should be fixed by r302679
>>
>>
>> Thanks Quentin,
>>
>> That reduces the slow-down when enabling globalisel at -O0 from 13% (on
>> r302453)  to 9.5% (on r302679) in my experiments.
>> The code size increase also reduces from just over 3% to 2.8%.
>>
>> Kristof
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>

Agreed. That was probably just luck before :)

-eric

On Fri, May 12, 2017 at 5:22 AM Diana Picus via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> It turns out that can be fixed by adding -lm to the link line, so I
> will probably convert it into a test-suite bug.
>
> I don't suppose it's crucial to handle the fabs intrinsic nicely at
-O0.
>
> On 12 May 2017 at 13:44, Diana Picus <diana.picus at linaro.org>
wrote:
> > Hi,
> >
> > I ran into a little snag on the test-suite:
> > https://bugs.llvm.org/show_bug.cgi?id=33021
> > It boils down to GlobalISel generating calls to fabs instead of using
> > FABSDr (so we get undefined references).
> >
> > Cheers,
> > Diana
> >
> > On 11 May 2017 at 18:40, Quentin Colombet <qcolombet at
apple.com> wrote:
> >> Hi Diana,
> >>
> >> Thanks for the summary.
> >>
> >> On May 11, 2017, at 4:01 AM, Diana Picus <diana.picus at
linaro.org>
> wrote:
> >>
> >> Hi all,
> >>
> >> I'm still running some validation on this, I'll send an
email when
> >> it's done. If that goes well I don't have anything against
making the
> >> switch.
> >>
> >> For the record, here's a summary of issues that were deferred
for
> >> later on (some of which are optimization-ish and we might decide
to
> >> never do at -O0 at all):
> >> * Crash in RegBankSelect for half fp types:
> >> https://bugs.llvm.org/show_bug.cgi?id=32560
> >>
> >>
> >> I’ll have a look.
> >>
> >> * Improving constant placement:
> http://bugs.llvm.org/show_bug.cgi?id=32561
> >>
> >>
> >> I’ve commented in the PR to mention the localizer technic I was
playing
> >> with, if someone wants to give it a try.
> >>
> >> * Fancy switch lowering
> >> * Transforming division-by-constant-power-of-2 into right shift
> >>
> >>
> >> AFAICT all the other issues that were brought up were fixed
(yay!).
> >>
> >> Cheers,
> >> Diana
> >>
> >>
> >> Cheers,
> >> -Quentin
> >>
> >>
> >>
> >> On 11 May 2017 at 08:44, Kristof Beyls via llvm-dev
> >> <llvm-dev at lists.llvm.org> wrote:
> >>
> >>
> >> On 10 May 2017, at 17:36, Quentin Colombet <qcolombet at
apple.com> wrote:
> >>
> >>
> >> MultiSource/Benchmarks/mediabench/mpeg2/mpeg2dec/mpeg2decode
(46%):
> Function
> >> Reference_IDCT: Probably due to creating all constants in the
entry BB +
> >> spilling floating point data through an X register:
> >>
> >> FastISel:
> >> fadd d0, d1, d0
> >> str d0, [sp,#528]
> >> GlobalISel:
> >> fadd d0, d1, d0
> >> fmov x9, d0
> >> stur x9, [x29,#-48]
> >>
> >>
> >> Good finding, I forgot to do stores in my previous fix. I’ll do
them
> >> shortly.
> >>
> >>
> >> Should be fixed by r302679
> >>
> >>
> >> Thanks Quentin,
> >>
> >> That reduces the slow-down when enabling globalisel at -O0 from
13% (on
> >> r302453)  to 9.5% (on r302679) in my experiments.
> >> The code size increase also reduces from just over 3% to 2.8%.
> >>
> >> Kristof
> >>
> >>
> >> _______________________________________________
> >> LLVM Developers mailing list
> >> llvm-dev at lists.llvm.org
> >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> >>
> >>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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