Topic created on: September 14, 2008 23:39 CDT by rman .

As Ive mentioned in a couple recent posts Im doing some work on an embedded PPC system, and I've been seeing a lot of interesting, and seemingly redundant code, eg:

ROM:00130930                 lbz     %r0, 2(%r3)
ROM:00130934                 lbz     %r9, 3(%r3)
ROM:00130938                 lbz     %r0, 2(%r3)
ROM:0013093C                 slwi    %r9, %r9, 8
ROM:00130940                 or      %r11, %r9, %r0

Simple code that makes r11 = (r3+3)(r3+2).  R3 is a memory buffer in this case.  The first and 3rd line appear to do exactly the same thing, and I'm curious if anyone can give some insight into why it would do that, outside of odd compiler behavior.

Thanks,