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From: foster@TED.CS.UIDAHO.EDU
Newsgroups: comp.lang.asm370
Subject: Re: Why use an LA instruction?
Message-ID: <9103071916.AA14119@ucbvax.Berkeley.EDU>
Date: 7 Mar 91 18:13:04 GMT
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Reply-To: IBM 370 Assembly Programming Discussion List
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It's a trick.  BALR loads the program mask into the lowest nibble of r4...or it
        used to.   I'll bet the LA 4,0(0,4) is just there to zero out the
        program mask.
This is not good code, as the program mask being loaded depends on the operating
systems (doesn't work that way in MVS/XA or MVS/ESA).

James