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

[Eric Christopher via 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
> >>
> >>
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