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From: Alexei Pytel <pytel@us.ibm.com> > > Well, the RISC code to check if a pointer is valid is: > > LQ R6, addr ; load pointer into R6, R7. set bit in exception reg if no > tag > > TXER nn ; trap if no tag > > to me that is software. The trap can be disabled by replacing the TXER > > instruction by a NOOP. > > The overhead is the TXER instruction and is not unacceptable. > > Are you saying that if you replace TXER instruction by NOOP and then go on > to use > untagged pointer, there will be no exception ? > in effect: yes. It is called a counterfeit pointer. People have known how to make these as long as there have been AS/400s. They are not my invention.
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