From: Leizhen (ThunderTown)
Sent: 16 December 2022 12:02
..
Moving the m68k version inside lib/string.c makes the test pass, too. So it must be related to the function being inline, and gcc making (incorrect) assumptions...Yes, it's the compiler's fault. I just replied David Laight: I added 'volatile' to prevent compiler optimizations, and it's OK now. diff --git a/arch/m68k/include/asm/string.h b/arch/m68k/include/asm/string.h index f759d944c449940..3db81e5a783c72a 100644 --- a/arch/m68k/include/asm/string.h +++ b/arch/m68k/include/asm/string.h @@ -42,9 +42,9 @@ static inline char *strncpy(char *dest, const char *src, size_t n) #define __HAVE_ARCH_STRCMP static inline int strcmp(const char *cs, const char *ct) { - char res; + signed char res; - asm ("\n" + asm volatile ("\n" "1: move.b (%0)+,%2\n" /* get *cs */ " cmp.b (%1)+,%2\n" /* compare a byte */ " jne 2f\n" /* not equal, break out */
Adding 'volatile' there shouldn't make any real difference. I'd double-check the asm constraints for the two pointers. They are modified by the asm, but the caller's variables must not be changed. I think that means they need to be normal 'input' parameters and the result must be in different register (early clobber?). Currently the pointers are "+r" - which I think means they are input-output and any caller-supplied variable is likely to get changed. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
