Fix bug in ARM memset implementation
The ARM implementation of memset has a bug when the fill-value is negative or outside the
[0, 255] range. To reproduce:
char array[256];
memset(array, -5, 256);
This is supposed to fill the array with int8 values -5, -5, -5, ... . On ARM, this does
not work because the implementation assumes the high bytes of the fill-value argument are
already zero. However in this test case they are filled with 1-bits. The aarch64 and x86_64
implementations do not have this problem: they first convert the fill-value to an unsigned
byte following the specification of memset.
With GCC one can use `memset(ptr, (-5 & 0xFF), size)` as a workaround, but for clang
users that does not work: clang optimizes the `& 0xFF` away because it assumes that
memset will do it.
Signed-off-by: Tom Bannink <tombannink@gmail.com>
Acked-by: Peter Korsgaard <peter@korsgaard.com>
Tom Bannink