The PAGE_COPY_THRESHOLD macro is meant to be overridden by
architecture-specific pagecopy.h, but it is currently done only by
mach; all other architectures use the default. Check to see if the
macro is defined in addition to whether it is set to a non-zero value.
Check wheter the compiler has the option -fno-tree-loop-distribute-patterns
to inhibit loop transformation to library calls and uses it on memset
and memmove default implementation to avoid recursive calls.
This patch includes optimized 64bit memcpy/memmove for Atom, Core 2 and
Core i7. It improves memcpy by up to 3X on Atom, up to 4X on Core 2 and
up to 1X on Core i7. It also improves memmove by up to 3X on Atom, up to
4X on Core 2 and up to 2X on Core i7.
