Re: Revised PPC assembly implementation

On Tue, 26 Apr 2005 09:00:45 +1000
Paul Mackerras [off-list ref] wrote:

The main loop seems to be taking about 560 cycles (assuming that
essentially all the time spent in my little test program is spent in
the main loop).  It contains about 1000 integer instructions, which
will take at least 500 cycles, as we have 2 ALUs.  So we are already
within about 10% of the theoretical optimum.

Time to bust out the altivec perhaps :)

Do a block with the integer ALUs in parallel with a block done using
Altivec :-)  There should be enough spare insn slots so that the loads
are absorbed properly.

Unlike UltraSPARC's VIS, with altivec you can reasonably do shifts and
rotates, which is the only reason I'm suggesting this.