From: Christian König > Sent: 15 April 2020 08:57 > Am 15.04.20 um 09:41 schrieb Jani Nikula: > > On Tue, 14 Apr 2020, Alex Deucher <alexdeucher@xxxxxxxxx> wrote: > >> On Tue, Apr 14, 2020 at 9:05 AM Bernard Zhao <bernard@xxxxxxxx> wrote: > >>> On some processors, the / operate will call the compiler`s div lib, > >>> which is low efficient, We can replace the / operation with shift, > >>> so that we can replace the call of the division library with one > >>> shift assembly instruction. > > This was applied already, and it's not in a driver I look after... but > > to me this feels like something that really should be > > justified. Using >> instead of / for multiples of 2 division mattered 20 > > years ago, I'd be surprised if it still did on modern compilers. > > I have similar worries, especially since we replace the "/ (4 * 2)" with > ">> 3" it's making the code just a bit less readable. > > And that the code runs exactly once while loading the driver and pushing > the firmware into the hardware. So performance is completely irrelevant > here. Force the division to be unsigned and the compiler will use a shift. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
