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From: mustard@sdrc.UUCP (Sandy Mustard)
Newsgroups: comp.arch
Subject: Re: Self-modifying code
Message-ID: <855@sdrc.UUCP>
Date: 13 Oct 89 00:24:10 GMT
References: <6481@pt.cs.cmu.edu> <9175@etana.tut.fi> <1619@atanasoff.cs.iastate.edu>
Organization: Structural Dynamics Research Corp., Cincinnati
Lines: 24

In article <1619@atanasoff.cs.iastate.edu>, hascall@atanasoff.cs.iastate.edu (John Hascall) writes:
> In article <9175@etana.tut.fi> pl@etana.tut.fi (Lehtinen Pertti) writes:
> 	    Well, how about the IBM 370 series.  (not exactly modern, I know)
> 	    If I recall correctly:
> 		       EX    mask,location
> 		       <next instruction>
>             location:  <target instruction>
> 	    Fetches the target instruction at "location" and ORs "mask" with
> 	    (some of) the target instruction and then executes the resulting
> 	    instruction.  Control resumes at "next instruction".
> John Hascall
> ISU Comp Center


To quote the 370/XA Principles of Operations manual,

"When the target instruction is a successful branching instruction, the
instruction address of the current PSW is replaced by the branch address
specified in the target instruction." 

thus control may resume at the target address of the branch instruction.

Sandy Mustard
mustard@sdrc.UU.NET