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 <[email protected]<mailto:[email protected]>>
Reviewed-by: Bin Meng [email protected]<mailto:[email protected]>
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
Rohde & Schwarz Asia Pte Ltd
9 Changi Business Park Vista, #01-01, Singapore 486 041
DID: 65-6307 0374 Fax: 65-6307 0300
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