linux-kernel - Re: Re: [PATCH v3 1/3] bits: introduce fixed-type genmasks

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Date: Wed, 21 Feb 2024 15:59:06 -0600
From: Lucas De Marchi <lucas.demarchi@...el.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
CC: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, Yury Norov
	<yury.norov@...il.com>, <linux-kernel@...r.kernel.org>,
	<dri-devel@...ts.freedesktop.org>, Jani Nikula <jani.nikula@...ux.intel.com>,
	<intel-xe@...ts.freedesktop.org>, <intel-gfx@...ts.freedesktop.org>, "Jani
 Nikula" <jani.nikula@...el.com>
Subject: Re: Re: [PATCH v3 1/3] bits: introduce fixed-type genmasks

On Wed, Feb 21, 2024 at 11:04:22PM +0200, Andy Shevchenko wrote:
>On Wed, Feb 21, 2024 at 10:30:02PM +0200, Dmitry Baryshkov wrote:
>> On Thu, 8 Feb 2024 at 09:45, Lucas De Marchi <lucas.demarchi@...el.com> wrote:
>
>...
>
>> > +#define BITS_PER_TYPE(type)    (sizeof(type) * BITS_PER_BYTE)
>
>Can sizeof() be used in assembly?
>
>...
>
>> > -#define __GENMASK(h, l) \
>> > -       (((~UL(0)) - (UL(1) << (l)) + 1) & \
>> > -        (~UL(0) >> (BITS_PER_LONG - 1 - (h))))
>> > -#define GENMASK(h, l) \
>> > -       (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
>
>> > +#define __GENMASK(t, h, l) \
>> > +       (GENMASK_INPUT_CHECK(h, l) + \
>> > +        (((t)~0ULL - ((t)(1) << (l)) + 1) & \
>> > +        ((t)~0ULL >> (BITS_PER_TYPE(t) - 1 - (h)))))
>
>Nevertheless, the use ~0ULL is not proper assembly, this broke initial
>implementation using UL() / ULL().

indeed.

>
>
>> > -#define __GENMASK_ULL(h, l) \
>> > -       (((~ULL(0)) - (ULL(1) << (l)) + 1) & \
>> > -        (~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h))))
>> > -#define GENMASK_ULL(h, l) \
>> > -       (GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l))
>
>Ditto.

problem here seems actually because of the cast to the final type. My
previous impl was avoiding that, but was too verbose compared to this.

I will look at reverting this.

Lucas De Marchi

>
>> > +#define GENMASK(h, l)          __GENMASK(unsigned long,  h, l)
>> > +#define GENMASK_ULL(h, l)      __GENMASK(unsigned long long, h, l)
>> > +#define GENMASK_U8(h, l)       __GENMASK(u8,  h, l)
>> > +#define GENMASK_U16(h, l)      __GENMASK(u16, h, l)
>> > +#define GENMASK_U32(h, l)      __GENMASK(u32, h, l)
>> > +#define GENMASK_U64(h, l)      __GENMASK(u64, h, l)
>>
>> This breaks drm-tip on arm64 architecture:
>>
>> arch/arm64/kernel/entry-fpsimd.S: Assembler messages:
>> 465arch/arm64/kernel/entry-fpsimd.S:271: Error: found 'l', expected: ')'
>> 466arch/arm64/kernel/entry-fpsimd.S:66: Info: macro invoked from here
>> 467arch/arm64/kernel/entry-fpsimd.S:271: Error: found 'l', expected: ')'
>> 468arch/arm64/kernel/entry-fpsimd.S:66: Info: macro invoked from here
>> 469arch/arm64/kernel/entry-fpsimd.S:271: Error: found 'l', expected: ')'
>> 470arch/arm64/kernel/entry-fpsimd.S:66: Info: macro invoked from here
>> 471arch/arm64/kernel/entry-fpsimd.S:271: Error: found 'l', expected: ')'
>> 472arch/arm64/kernel/entry-fpsimd.S:66: Info: macro invoked from here
>> 473arch/arm64/kernel/entry-fpsimd.S:271: Error: unexpected characters
>> following instruction at operand 3 -- `bic x2,x1,(0+(((unsigned
>> long)~0ULL-((unsigned long)(1)<<(0))+1)&((unsigned
>> long)~0ULL>>((sizeof(unsigned long)*8)-1-(3)))))'
>> 474arch/arm64/kernel/entry-fpsimd.S:66: Info: macro invoked from here
>> 475arch/arm64/kernel/entry-fpsimd.S:282: Error: found 'l', expected: ')'
>> 476arch/arm64/kernel/entry-fpsimd.S:98: Info: macro invoked from here
>> 477arch/arm64/kernel/entry-fpsimd.S:282: Error: found 'l', expected: ')'
>> 478arch/arm64/kernel/entry-fpsimd.S:98: Info: macro invoked from here
>> 479arch/arm64/kernel/entry-fpsimd.S:282: Error: found 'l', expected: ')'
>> 480arch/arm64/kernel/entry-fpsimd.S:98: Info: macro invoked from here
>> 481arch/arm64/kernel/entry-fpsimd.S:282: Error: found 'l', expected: ')'
>> 482arch/arm64/kernel/entry-fpsimd.S:98: Info: macro invoked from here
>> 483arch/arm64/kernel/entry-fpsimd.S:282: Error: unexpected characters
>> following instruction at operand 3 -- `bic x2,x1,(0+(((unsigned
>> long)~0ULL-((unsigned long)(1)<<(0))+1)&((unsigned
>> long)~0ULL>>((sizeof(unsigned long)*8)-1-(3)))))'
>> 484arch/arm64/kernel/entry-fpsimd.S:98: Info: macro invoked from here
>
>-- 
>With Best Regards,
>Andy Shevchenko
>
>