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

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Date: Wed, 21 Feb 2024 23:04:22 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Lucas De Marchi <lucas.demarchi@...el.com>,
	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: [PATCH v3 1/3] bits: introduce fixed-type genmasks

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().


> > -#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.

> > +#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