Date: Tue, 8 Dec 2015 08:57:04 +0100 From: "Ranjan1018 ." <214748mv@gmail.com> To: araujo@freebsd.org Cc: Michael McConville <mmcco@mykolab.com>, freebsd-current <freebsd-current@freebsd.org> Subject: Re: [PATCH] XOR uses Message-ID: <CACyC=qY5neO%2BF%2B9ds8JtSHixssc=crGFW==Fa0KpAOaoR0z0mQ@mail.gmail.com> In-Reply-To: <CAOfEmZiwq0vH6vN34c=3-0PJL1gTNjOjksNyQR1Ojve%2BuPbRYA@mail.gmail.com> References: <20151208031327.GA17554@thinkpad.swarthmore.edu> <CAOfEmZiwq0vH6vN34c=3-0PJL1gTNjOjksNyQR1Ojve%2BuPbRYA@mail.gmail.com>
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2015-12-08 5:40 GMT+01:00 Marcelo Araujo <araujobsdport@gmail.com>:
> Hi Michael,
>
> What would be the advantage of it?
> I still prefer explicit than implicit. The current code is much more
> readable.
>
> Best,
>
> 2015-12-08 11:13 GMT+08:00 Michael McConville <mmcco@mykolab.com>:
>
> > A minor simplification patch:
> >
> >
> > Index: sys/arm/allwinner/a10_gpio.c
> > ===================================================================
> > --- sys/arm/allwinner/a10_gpio.c (revision 291978)
> > +++ sys/arm/allwinner/a10_gpio.c (working copy)
> > @@ -356,10 +356,7 @@
> > sc = device_get_softc(dev);
> > A10_GPIO_LOCK(sc);
> > data = A10_GPIO_READ(sc, A10_GPIO_GP_DAT(bank));
> > - if (data & (1 << pin))
> > - data &= ~(1 << pin);
> > - else
> > - data |= (1 << pin);
> > + data ^= (1 << pin);
> > A10_GPIO_WRITE(sc, A10_GPIO_GP_DAT(bank), data);
> > A10_GPIO_UNLOCK(sc);
> >
> > Index: sys/arm/altera/socfpga/socfpga_gpio.c
> > ===================================================================
> > --- sys/arm/altera/socfpga/socfpga_gpio.c (revision 291978)
> > +++ sys/arm/altera/socfpga/socfpga_gpio.c (working copy)
> > @@ -336,10 +336,7 @@
> >
> > GPIO_LOCK(sc);
> > reg = READ4(sc, GPIO_SWPORTA_DR);
> > - if (reg & (1 << i))
> > - reg &= ~(1 << i);
> > - else
> > - reg |= (1 << i);
> > + reg ^= (1 << i);
> > WRITE4(sc, GPIO_SWPORTA_DR, reg);
> > GPIO_UNLOCK(sc);
> >
> > Index: sys/arm/rockchip/rk30xx_gpio.c
> > ===================================================================
> > --- sys/arm/rockchip/rk30xx_gpio.c (revision 291978)
> > +++ sys/arm/rockchip/rk30xx_gpio.c (working copy)
> > @@ -375,10 +375,7 @@
> > return (EINVAL);
> > RK30_GPIO_LOCK(sc);
> > data = RK30_GPIO_READ(sc, RK30_GPIO_SWPORT_DR);
> > - if (data & (1U << pin))
> > - data &= ~(1U << pin);
> > - else
> > - data |= (1U << pin);
> > + data ^= (1U << pin);
> > RK30_GPIO_WRITE(sc, RK30_GPIO_SWPORT_DR, data);
> > RK30_GPIO_UNLOCK(sc);
> >
> > Index: sys/arm/samsung/exynos/exynos5_pad.c
> > ===================================================================
> > --- sys/arm/samsung/exynos/exynos5_pad.c (revision 291978)
> > +++ sys/arm/samsung/exynos/exynos5_pad.c (working copy)
> > @@ -722,10 +722,7 @@
> >
> > GPIO_LOCK(sc);
> > reg = READ4(sc, bank.port, bank.con + 0x4);
> > - if (reg & (1 << pin_shift))
> > - reg &= ~(1 << pin_shift);
> > - else
> > - reg |= (1 << pin_shift);
> > + reg ^= (1 << pin_shift);
> > WRITE4(sc, bank.port, bank.con + 0x4, reg);
> > GPIO_UNLOCK(sc);
> >
> > Index: sys/dev/nand/nandsim_ctrl.c
> > ===================================================================
> > --- sys/dev/nand/nandsim_ctrl.c (revision 291978)
> > +++ sys/dev/nand/nandsim_ctrl.c (working copy)
> > @@ -388,9 +388,6 @@
> > rand = random();
> > if ((rand % 1000000) < chip->error_ratio) {
> > bit = rand % 8;
> > - if (*byte & (1 << bit))
> > - *byte &= ~(1 << bit);
> > - else
> > - *byte |= (1 << bit);
> > + *byte ^= (1 << bit);
> > }
> > }
> >
>
Hi,
I prefer the syntax in the patch:
- the semantic is more clear for me: if you want to flip a bit you should
use xor
- it saves, probably, some bytes of assembly code
Regards
Maurizio
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