• Stafford Horne's avatar
    openrisc: Add optimized memcpy routine · f5d45dc9
    Stafford Horne authored
    The generic memcpy routine provided in kernel does only byte copies.
    Using word copies we can lower boot time and cycles spend in memcpy
    quite significantly.
    
    Booting on my de0 nano I see boot times go from 7.2 to 5.6 seconds.
    The avg cycles in memcpy during boot go from 6467 to 1887.
    
    I tested several algorithms (see code in previous patch mails)
    
    The implementations I tested and avg cycles:
      - Word Copies + Loop Unrolls + Non Aligned    1882
      - Word Copies + Loop Unrolls                  1887
      - Word Copies                                 2441
      - Byte Copies + Loop Unrolls                  6467
      - Byte Copies                                 7600
    
    In the end I ended up going with Word Copies + Loop Unrolls as it
    provides best tradeoff between simplicity and boot speedups.
    Signed-off-by: default avatarStafford Horne <shorne@gmail.com>
    f5d45dc9
TODO.openrisc 611 Bytes