On Thu, 2018-09-20 at 16:45:05 UTC, Breno Leitao wrote: > Moving TIF_32BIT to use bit 20 instead of 4 in the task flag field. > > This change is making room for an upcoming new task macro > (_TIF_SYSCALL_EMU) which is preferred to set a bit in the lower 16-bits > part of the word. > > This upcoming flag macro will take part in a composed macro > (_TIF_SYSCALL_DOTRACE) which will contain other flags as well, and it is > preferred that the whole _TIF_SYSCALL_DOTRACE macro only sets the lower 16 > bits of a word, so, it could be handled using immediate operations (as load > immediate, add immediate, ...) where the immediate operand (SI) is limited > to 16-bits. > > Another possible solution would be using the LOAD_REG_IMMEDIATE() macro > to load a full 64-bits word immediate, but it takes 5 operations instead of > one. > > Having TIF_32BITS being redefined to use an upper bit is not a problem > since there is only one place in the assembly code where TIF_32BIT is being > used, and it could be replaced with an operation with right shift (addis), > since it is used alone, i.e. not being part of a composed macro, which has > different bits set, and would require LOAD_REG_IMMEDIATE(). > > Tested on a 64 bits Big Endian machine running a 32 bits task. > > Signed-off-by: Breno Leitao <lei...@debian.org>
Series applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/16d7c69c898531210d13dbd1eb2053 cheers
