On Mon, Jul 11, 2022 at 05:05:04PM +0200, Arnd Bergmann wrote: > Is there any value in building for -mcpu=440 or -mcpu=464 when targeting a > 476?
The original 440 had a very short pipeline. Later IBM 4xx have a longer pipeline. Getting this right (with -mtune=, or just with -mcpu=) is important for performance. So, no? > Maybe add another !PPC_47x dependency for the first two. Ideally we would also > enforce that 440/464 based boards cannot be selected together with 476, though > I guess that is a separate issue. > > Is there a practical difference between 440 and 464 when building kernels? > gcc seems to treat them the same way, so maybe one option for both is enough > here. -mcpu= is used as the default for -mtune=, so that is always a consideration. PPC464 is treated the same as PPC440 in binutils as well, so I don't think there is any issue there. Segher
