[U-Boot] instruction "xchgb" for x86_64

[U-Boot] instruction "xchgb" for x86_64

[James Wang]

Hi Bin
 
>> This is James and am working on u-boot to bring back MinGW tool chain for cross compiling host tools for Windows on Linux. After complete the code, I plan to generate a patch for community review.

>Do you mean cross compiling U-Boot's mkimage tool for Windows on Linux using gcc-mingw-w64? Do you want to support building U-Boot on Windows as well?

Yes, I am compiling with MinGW-w64, more specifically x86_64-w64-mingw32-gcc on Linux. I don't have setup to build host tools on Windows for now. Maybe I could have a try.
 
 
Best regards
James Wang Jinmin

[U-Boot] instruction "xchgb" for x86_64

[James Wang]

> 
> Hi,
> 
> (James please can you use plain-text email for the mailing list?)
  
OK. Thanks Simon for pointing out this. I am using outlook, so most likely will have "newline" difference. Hope can find a way out for this.
 
> 
> For chromebook_link64 I get:
> 
> output: '/usr/local/google/home/sjg/cosarm/src/third_party/u-
> boot/files/arch/x86/include/asm/byteorder.h:
> Assembler messages:
> /usr/local/google/home/sjg/cosarm/src/third_party/u-
> boot/files/arch/x86/include/asm/byteorder.h:22:
> Error: register type mismatch for `xchg'
> make[2]: *** [/usr/local/google/home/sjg/cosarm/src/third_party/u-
> boot/files/scripts/Makefile.build:278:
> net/tftp.o] Error 1
> make[2]: *** Waiting for unfinished jobs....
> /usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/net/net.c:
> In function 'net_process_received_packet':
> /usr/local/google/home/sjg/cosarm/src/third_party/u-
> boot/files/net/net.c:1324:1:
> error: extended registers have no high halves  }  ^
> /usr/local/google/home/sjg/cosarm/src/third_party/u-
> boot/files/arch/x86/include/asm/byteorder.h:
> Assembler messages:
> /usr/local/google/home/sjg/cosarm/src/third_party/u-
> boot/files/arch/x86/include/asm/byteorder.h:22:
> Error: register type mismatch for `xchg'
> /usr/local/google/home/sjg/cosarm/src/third_party/u-
> boot/files/arch/x86/include/asm/byteorder.h:22:
> Error: register type mismatch for `xchg'
> /usr/local/google/home/sjg/cosarm/src/third_party/u-
> boot/files/arch/x86/include/asm/byteorder.h:22:
> Error: register type mismatch for `xchg'
> make[2]: *** [/usr/local/google/home/sjg/cosarm/src/third_party/u-
> boot/files/scripts/Makefile.build:278:
> net/net.o] Error 1
> make[1]: *** [/usr/local/google/home/sjg/cosarm/src/third_party/u-
> boot/files/Makefile:1588:
> net] Error 2
> make[1]: *** Waiting for unfinished jobs....
> make: *** [Makefile:148: sub-make] Error 2
> 
> Perhaps there is another way to fix this?
> 

I tested two toolchains: 
1. With gcc version 7.3-win32 20180312 (the MinGW-w64 cross compiling), it can assemble the xchgb without error.
2. With gcc version 7.3.0 (Ubuntu 7.3.0-27ubuntu1~18.04), it uses /usr/include/x86_64-linux-gnu/asm/byteorder.h, (not the one in uboot), and that file is only to include the <little_endian.h> file

As the assembler you use reports error for xchgb  (no matter what's the cause), we may use ONLY the C version of implementation and remove the assembly version and relevant  CONFIG_IS_ENABLED checking (if performance is not critical here)?

How do you think, Simon and Bin?

Best regards
James Wang Jinmin

[U-Boot] instruction "xchgb" for x86_64

[Simon Glass]

Hi,

(James please can you use plain-text email for the mailing list?)

On Wed, 14 Aug 2019 at 01:35, Bin Meng <bmeng.cn@gmail.com> wrote:
>
> Hi James,
>
> On Wed, Aug 14, 2019 at 1:08 PM James Wang <James.Wang@rohde-schwarz.com> wrote:
>>
>> Hi Simon,
>>
>>
>>
>> This is James and am working on u-boot to bring back MinGW tool chain for cross compiling host tools for Windows on Linux. After complete the code, I plan to generate a patch for community review.
>
>
> Do you mean cross compiling U-Boot's mkimage tool for Windows on Linux using gcc-mingw-w64? Do you want to support building U-Boot on Windows as well?
>
>>
>>
>>
>> During work, I face an compiling error in file <arch/x86/include/asm/byteorder.h> with macro CONFIG_IS_ENABLED. After some background study, seems this macro should not be available when compiling host tools.
>>
>>
>>
>> After check history, it’s from 909780506773a9b09ae88cb267dbfa6a8d0caa7b on 2017-01-16 22:04:04, Below is the log message
>>
>>
>>
>>    x86: Fix up byteorder.h for x86_64
>>
>>
>>
>>     Remove the very old x86 code and add support for 64-bit.
>>
>>
>>
>>     Signed-off-by: Simon Glass <sjg@chromium.org>
>>
>> Reviewed-by: Bin Meng bmeng.cn at gmail.com
>>
>>
>>
>> Below are the relevant changes.
>>
>>
>>
>> +#define _constant_swab16(x) ((__u16)(                                             \
>>
>> +      (((__u16)(x) & (__u16)0x00ffU) << 8) |                            \
>>
>> +      (((__u16)(x) & (__u16)0xff00U) >> 8)))
>>
>> +
>>
>> static __inline__ __u16 ___arch__swab16(__u16 x)
>>
>> {
>>
>> +#if CONFIG_IS_ENABLED(X86_64)
>>
>> +      return _constant_swab16(x);
>>
>> +#else
>>
>>        __asm__("xchgb %b0,%h0"                   /* swap bytes                */ \
>>
>>                    : "=q" (x) \
>>
>>                    :  "0" (x)); \
>>
>>                    return x;
>>
>> +#endif
>>
>> }
>>
>>
>>
>> I am not familiar with x86 instructions and not understand the purpose of this change, is it because instruction “xchgb” not available on 64-bit architecture or something else?
>
>
> I can't remember the details of why Simon changed this. xchgb is available in 64-bit. We probably need revert this change, Simon?

For chromebook_link64 I get:

output: '/usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/arch/x86/include/asm/byteorder.h:
Assembler messages:
/usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/arch/x86/include/asm/byteorder.h:22:
Error: register type mismatch for `xchg'
make[2]: *** [/usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/scripts/Makefile.build:278:
net/tftp.o] Error 1
make[2]: *** Waiting for unfinished jobs....
/usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/net/net.c:
In function 'net_process_received_packet':
/usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/net/net.c:1324:1:
error: extended registers have no high halves
 }
 ^
/usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/arch/x86/include/asm/byteorder.h:
Assembler messages:
/usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/arch/x86/include/asm/byteorder.h:22:
Error: register type mismatch for `xchg'
/usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/arch/x86/include/asm/byteorder.h:22:
Error: register type mismatch for `xchg'
/usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/arch/x86/include/asm/byteorder.h:22:
Error: register type mismatch for `xchg'
make[2]: *** [/usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/scripts/Makefile.build:278:
net/net.o] Error 1
make[1]: *** [/usr/local/google/home/sjg/cosarm/src/third_party/u-boot/files/Makefile:1588:
net] Error 2
make[1]: *** Waiting for unfinished jobs....
make: *** [Makefile:148: sub-make] Error 2

Perhaps there is another way to fix this?

Regards,
Simon

[U-Boot] instruction "xchgb" for x86_64

[Bin Meng]

Hi James,

On Wed, Aug 14, 2019 at 1:08 PM James Wang <James.Wang@rohde-schwarz.com>
wrote:

> Hi Simon,
>
>
>
> This is James and am working on u-boot to bring back MinGW tool chain for
> cross compiling host tools for Windows on Linux. After complete the code, I
> plan to generate a patch for community review.
>

Do you mean cross compiling U-Boot's mkimage tool for Windows on Linux
using gcc-mingw-w64? Do you want to support building U-Boot on Windows as
well?


>
>
> During work, I face an compiling error in file
> <arch/x86/include/asm/byteorder.h> with macro *CONFIG_IS_ENABLED*. After
> some background study, seems this macro should not be available when
> compiling host tools.
>
>
>
> After check history, it’s from 909780506773a9b09ae88cb267dbfa6a8d0caa7b on
> 2017-01-16 22:04:04, Below is the log message
>
>
>
> *   x86: Fix up byteorder.h for x86_64*
>
>
>
> *    Remove the very old x86 code and add support for 64-bit.*
>
>
>
> *    Signed-off-by: Simon Glass <sjg at chromium.org <sjg@chromium.org>>*
>
> *Reviewed-by: Bin Meng bmeng.cn at gmail.com <bmeng.cn@gmail.com>*
>
>
>
> Below are the relevant changes.
>
>
>
> *+#define _constant_swab16(x)
> ((__u16)(                                             \*
>
> *+      (((__u16)(x) & (__u16)0x00ffU) << 8) |
> \*
>
> *+      (((__u16)(x) & (__u16)0xff00U) >> 8)))*
>
> *+*
>
> *static __inline__ __u16 ___arch__swab16(__u16 x)*
>
> *{*
>
> *+#if CONFIG_IS_ENABLED(X86_64)                          *
>
> *+      return _constant_swab16(x);*
>
> *+#else*
>
> *       __asm__("xchgb %b0,%h0"                   /* swap
> bytes                */ \*
>
> *                   : "=q" (x) \*
>
> *                   :  "0" (x)); \*
>
> *                   return x;*
>
> *+#endif*
>
> *}*
>
>
>
> I am not familiar with x86 instructions and not understand the purpose of
> this change, is it because instruction “xchgb” not available on 64-bit
> architecture or something else?
>

I can't remember the details of why Simon changed this. xchgb is available
in 64-bit. We probably need revert this change, Simon?

Regards,
Bin
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[U-Boot] instruction "xchgb" for x86_64

[James Wang]

Hi Simon,

This is James and am working on u-boot to bring back MinGW tool chain for cross compiling host tools for Windows on Linux. After complete the code, I plan to generate a patch for community review.

During work, I face an compiling error in file <arch/x86/include/asm/byteorder.h> with macro CONFIG_IS_ENABLED. After some background study, seems this macro should not be available when compiling host tools.

After check history, it's from 909780506773a9b09ae88cb267dbfa6a8d0caa7b on 2017-01-16 22:04:04, Below is the log message

   x86: Fix up byteorder.h for x86_64

    Remove the very old x86 code and add support for 64-bit.

    Signed-off-by: Simon Glass <sjg at chromium.org<mailto:sjg@chromium.org>>
Reviewed-by: Bin Meng bmeng.cn at gmail.com<mailto:bmeng.cn@gmail.com>

Below are the relevant changes.

+#define _constant_swab16(x) ((__u16)(                                             \
+      (((__u16)(x) & (__u16)0x00ffU) << 8) |                            \
+      (((__u16)(x) & (__u16)0xff00U) >> 8)))
+
static __inline__ __u16 ___arch__swab16(__u16 x)
{
+#if CONFIG_IS_ENABLED(X86_64)
+      return _constant_swab16(x);
+#else
       __asm__("xchgb %b0,%h0"                   /* swap bytes                */ \
                   : "=q" (x) \
                   :  "0" (x)); \
                   return x;
+#endif
}

I am not familiar with x86 instructions and not understand the purpose of this change, is it because instruction "xchgb" not available on 64-bit architecture or something else?

Thanks!


Best regards
James Wang Jinmin

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