RE: [PATCH] Correct cpu_flags for CPU_ANY_AVX512BW_FLAGS

["Cui, Lili" <lili.cui@intel.com>]

> -----Original Message-----
> From: H.J. Lu <hjl.tools@gmail.com>
> Sent: Friday, June 24, 2022 9:56 AM
> To: Beulich, Jan <JBeulich@suse.com>
> Cc: binutils@sourceware.org; Cui, Lili <lili.cui@intel.com>
> Subject: Re: [PATCH] Correct cpu_flags for CPU_ANY_AVX512BW_FLAGS
> 
> On Thu, Jun 23, 2022 at 9:31 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Thu, Jun 23, 2022 at 9:08 AM Jan Beulich <jbeulich@suse.com> wrote:
> > >
> > > On 23.06.2022 18:04, H.J. Lu wrote:
> > > > On Thu, Jun 23, 2022 at 1:08 AM Cui, Lili <lili.cui@intel.com> wrote:
> > > >>
> > > >>
> > > >>
> > > >>> -----Original Message-----
> > > >>> From: Jan Beulich <jbeulich@suse.com>
> > > >>> Sent: Thursday, June 23, 2022 3:30 PM
> > > >>> To: Cui, Lili <lili.cui@intel.com>
> > > >>> Cc: binutils@sourceware.org; hjl.tools@gmail.com
> > > >>> Subject: Re: [PATCH] Correct cpu_flags for
> > > >>> CPU_ANY_AVX512BW_FLAGS
> > > >>>
> > > >>> On 23.06.2022 09:14, Cui,Lili wrote:
> > > >>>> This patch is to correct cpu_flags for CPU_ANY_AVX512BW_FLAGS.
> > > >>>> Make check-gas is ok.
> > > >>>> Ok for master?
> > > >>>>
> > > >>>> Thanks,
> > > >>>> Lili.
> > > >>>>
> > > >>>> Change it from "CPU_ANY_AVX512_FP16_FLAGS" to
> "CpuAVX512_FP16"
> > > >>>
> > > >>> You don't say what's wrong with what there is right now. I for
> > > >>> one think what we have is correct: If one disables BW, _all_ its
> > > >>> dependents should be disabled as well, which transitively means all
> dependents of FP16.
> > > >>>
> > > >> Hi Jan,
> > > >> Agree with that " If one disables BW, _all_ its dependents should be
> disabled as well ".
> > > >> I saw the form of "CPU_ANY_AVX512F_FLAGS" today, and to be
> consistent with it, I thought "CPU_ANY_AVX512_FP16_FLAGS" was wrong at
> that time. But after reading your email, I found "CPU_ANY_AVX512F_FLAGS"
> to be the only one that uses cpu_flags instead of CPU_ANY* .
> > > >>
> > > >> { "CPU_ANY_AVX512F_FLAGS",
> > > >>
> "CpuAVX512F|CpuAVX512CD|CpuAVX512ER|CpuAVX512PF|CpuAVX512DQ|
> CPU_A
> > > >>
> NY_AVX512BW_FLAGS|CpuAVX512VL|CpuAVX512IFMA|CpuAVX512VBMI|C
> puAVX5
> > > >>
> 12_4FMAPS|CpuAVX512_4VNNIW|CpuAVX512_VPOPCNTDQ|CpuAVX512_V
> BMI2|Cp
> > > >>
> uAVX512_VNNI|CpuAVX512_BITALG|CpuAVX512_BF16|CpuAVX512_VP2INT
> ERSE
> > > >> CT" },
> > > >>
> > > >> Regards,
> > > >> Lili.
> > > >>
> > > >>> Jan
> > > >>>
> > > >>>> opcodes/
> > > >>>>
> > > >>>>     * i386-gen.c (cpu_flag_init): Change cpu_flags of
> > > >>>>     CPU_ANY_AVX512BW_FLAGS.
> > > >>>> ---
> > > >>>>  opcodes/i386-gen.c | 2 +-
> > > >>>>  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >>>>
> > > >>>> diff --git a/opcodes/i386-gen.c b/opcodes/i386-gen.c index
> > > >>>> d18a7d2754..5dc224efdb 100644
> > > >>>> --- a/opcodes/i386-gen.c
> > > >>>> +++ b/opcodes/i386-gen.c
> > > >>>> @@ -382,7 +382,7 @@ static initializer cpu_flag_init[] =
> > > >>>>    { "CPU_ANY_AVX512DQ_FLAGS",
> > > >>>>      "CpuAVX512DQ" },
> > > >>>>    { "CPU_ANY_AVX512BW_FLAGS",
> > > >>>> -    "CpuAVX512BW|CPU_ANY_AVX512_FP16_FLAGS" },
> > > >>>> +    "CpuAVX512BW|CpuAVX512_FP16" },
> > > >>>>    { "CPU_ANY_AVX512VL_FLAGS",
> > > >>>>      "CpuAVX512VL" },
> > > >>>>    { "CPU_ANY_AVX512IFMA_FLAGS",
> > > >>
> > > >
> > > > Since CPU_ANY_AVX512_FP16_FLAGS is the same as CpuAVX512_FP16,
> > > > this change is nop.  On the other hand, CPU_ANY shouldn't be used
> > > > to define another CPU_ANY.
> > >
> > > Why? Imo that's exactly how it should be, as long as the purpose of
> > > CPU_ANY_* is the use for processing of negative .arch directives.
> > >
> >
> > Assuming AVX512_FP16 also requires BMI2, when AVX512F is disabled,
> > AVX512_FP16 should be disabled, but not BMI2.
> >
> 
> I was wrong.  The current code isn't wrong since
> 
>  { "CPU_ANY_AVX512BW_FLAGS",
>    "CpuAVX512BW|CPU_ANY_AVX512_FP16_FLAGS" },
> 
> indicates that disabling AVX512BW will also disable AVX512BW +
> AVX512F16 + any ISAs which
> depend on AVX512FP16.   If there is another ISA which depends on
> AVX512FP16, we don't
> need to change CPU_ANY_AVX512BW_FLAGS.
> 

Agree with you, Jan is right. The current code is correct, we don't need any changes here.

Thanks,
Lili.

> --
> H.J.