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Re: [PATCH v4 1/6] xen: implement byteswap
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Lin Liu <lin.liu@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 23 May 2022 13:00:02 +0200
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Mon, 23 May 2022 11:00:19 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 23.05.2022 12:07, Roger Pau Monné wrote:
> On Mon, May 23, 2022 at 05:52:17AM -0400, Lin Liu wrote:
>> diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h
>> index 933aec09a9..ae029afa14 100644
>> --- a/xen/include/xen/compiler.h
>> +++ b/xen/include/xen/compiler.h
>> @@ -185,4 +185,28 @@
>> # define CLANG_DISABLE_WARN_GCC_COMPAT_END
>> #endif
>>
>> +#ifndef __has_builtin
>> +/*
>> + * Backwards compatibility for GCC < 10.
>> + * All supported versions of Clang support __has_builtin
>> + * */
>> +#define __has_builtin(x) GCC_has ## x
>> +
>> +#define GCC_has__builtin_bswap16 (CONFIG_GCC_VERSION >= 40800)
>> +#define GCC_has__builtin_bswap32 (CONFIG_GCC_VERSION >= 40400)
>> +#define GCC_has__builtin_bswap64 (CONFIG_GCC_VERSION >= 40400)
>> +#endif
>> +
>> +#ifndef __ORDER_LITTLE_ENDIAN__
>> +# define __ORDER_LITTLE_ENDIAN__ 1234
>> +#endif
>> +
>> +#ifndef __ORDER_BIG_ENDIAN__
>> +# define __ORDER_BIG_ENDIAN__ 4321
>> +#endif
>> +
>> +/* Indirect macros required for expanded argument pasting. */
>> +#define PASTE_(a, b) a ## b
>> +#define PASTE(a, b) PASTE_(a, b)
>
> I think it would be better if byteswap.h included lib.h, rather than
> moving the PASTE define into compiler.h.
+1
> Likewise the __ORDER_{BIG,LITTLE}_ENDIAN__ defines would be better
> placed in byteswap.h itself if possible IMO, since it's not strictly
> related to the compiler.
These need to live in per-arch headers, i.e. asm/byteorder.h.
Jan
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