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

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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@xxxxxxxxx> 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





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