Messages in this thread | | | Subject | Re: [PATCH] powerpc: sysdev: cpm1: Optimise gpio bit calculation | From | Christophe LEROY <> | Date | Tue, 21 Mar 2017 16:04:40 +0100 |
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Le 10/03/2017 à 16:41, Segher Boessenkool a écrit : > On Fri, Mar 10, 2017 at 03:41:23PM +0100, Christophe LEROY wrote: >>>>>> gpio_get() and gpio_set() are used extensively by some GPIO based >>>>>> drivers like SPI, NAND, so it may be worth it as it doesn't impair >>>>>> readability (if anyone prefers, we could write (1 << 31) >> i instead >>>>>> of 0x80000000 >> i ) >>>>> 1 << 31 is undefined behaviour, of course. >>>> Shall it be 1U << 31 ? >>> Sure, that works. "1 << (31 - i)" is most readable (but it doesn't yet >>> generate the code you want). >> Euh .... I'm a bit lost. Do you mean the form we have today is the >> driver is wrong ? > Heh, yes. But is't okay with GCC, so don't worry about it. > > The point is that "0x80000000 >> i" is less readable. > > FYI, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80131
Christophe
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