Messages in this thread | | | From | Andreas Schwab <> | Subject | Re: [PATCH] asm-generic/bitops/fls64.h | Date | Tue, 13 May 2008 16:35:25 +0200 |
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Russell King <rmk+lkml@arm.linux.org.uk> writes:
> On Tue, May 13, 2008 at 03:24:13PM +0200, Alexander van Heukelum wrote: >> On Tue, 13 May 2008 16:29:04 +0400, "Nickolay Vinogradov" >> <nickolay@protei.ru> said: >> > Alexander van Heukelum пишет: >> > >> > > Hi Nickolay, >> > > >> > > The change is ok, I guess, but the cast should be a no-op (fls >> > > takes an int, which is always 32 bit in linux). What is the problem >> > > you are seeing? Does fls64() return a wrong value in some cases? If >> > > so, what cpu? Which values? >> > > >> > > Why would this be a bug on big endian systems only? There is no >> > > pointer magic involved, so the compiler should take care of the >> > > casts in a correct way. >> > > >> > > Maybe you see a compiler warning? Which compiler version? >> > > >> > > (also note that current (development) kernels now have separate >> > > versions for 32-bit and 64-bit environments.) >> > >> > Because fls() is a macro for asm-arm: >> > >> > #define fls(x) \ >> > ( __builtin_constant_p(x) ? constant_fls(x) : \ >> > ({ int __r; asm("clz\t%0, %1" : "=r"(__r) : "r"(x) : "cc"); >> > 32-__r; }) ) >> > >> > We can fix it right here: > > No. "fls" is for finding the last set bit in an _int_. It is not > supposed to have random crap passed to it, such as types longer than > sizeof(int).
If you write fls as an (inline) function then the argument is implicitly converted.
Andreas.
-- Andreas Schwab, SuSE Labs, schwab@suse.de SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different." -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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