Patent on aligned memcpy

[mrs at wrs dot com (Mike Stump)]

>From http://www.patents.ibm.com/details?patent_number=5706483:

ABSTRACT:

A method and apparatus for efficiently transferring a data block of
bytes from a source to a destination in memory of a computer
system. The method transfers bytes in multiple-byte words on
word-aligned boundaries of memory as much as possible to reduce the
number of fetches and writes and the number of memory cycles required
to execute the transfer. For handling data block transfers of various
sizes and locations, the method is implemented in a compiler that
compiles different portions of code at run time into a block of code
that is then immediately executed. The compiler employs a state
machine stored in memory and having a plurality of states. Each state
is associated with a portion of code for aligning a destination
address or for transferring bytes in multiple-byte words on
word-aligned boundaries. The states correspond to different starting
source and destination addresses. A number of state machines are
provided corresponding to the different color formats (bits per pixel)
that may exists in the source and destination.