Thank you for your detail answer :) , I see them now.
Best regards
Murray Jensen wrote:
On Sat, 04 Jan 2003 10:45:27 +0800, YanMin Qiao sepherosa@sohu.com writes:
First thanks for your answer, howerever, my question is Why we copy _forward_ when _memory address_ <CFG_MONITOR_BASE, but when _memory address_>=CFG_MONITOR_BASE we will have to _copy backword_? Is it because some overlapping problem when copy?
Yes. It is generic memory copying code - if it is at all possible that the copy might overwrite the destination then it goes backwards, instead of forwards. It shouldn't make a lot of difference either way (I guess I can imagine a scenario where it stuffs up some fancy pre-fetching in the CPU, which might make it go half or a third of the speed, but its not likely).
Be careful with the first "bge" above - it isn't testing the result of the previous instruction, it is testing the result of the "cmplw" done quite a few instructions beforehand and stored in "cr1" i.e. it will branch if "r3" (the destination address) is >= "r4" (the source address) i.e. if it is possible that the copy will overwrite the source.
thanks, I know
OK, I was just trying to be thorough. Cheers! Murray... -- Murray Jensen, CSIRO Manufacturing & Infra. Tech. Phone: +61 3 9662 7763 Locked Bag No. 9, Preston, Vic, 3072, Australia. Fax: +61 3 9662 7853 Internet: Murray.Jensen@csiro.au
Hymod project: http://www.msa.cmst.csiro.au/projects/Hymod/
To the extent permitted by law, CSIRO does not represent, warrant and/or guarantee that the integrity of this communication has been maintained or that the communication is free of errors, virus, interception or interference.
The information contained in this e-mail may be confidential or privileged. Any unauthorised use or disclosure is prohibited. If you have received this e-mail in error, please delete it immediately and notify Murray Jensen on +61 3 9662 7763. Thank you.