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From: XRJDM@SCFVM.BITNET (Joe McMahon)
Newsgroups: comp.lang.asm370
Subject: Re: Why use an LA instruction?
Message-ID: <9103042109.AA08710@ucbvax.Berkeley.EDU>
Date: 4 Mar 91 16:32:35 GMT
References: <PGIFFORD@ALLEGVM>
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Reply-To: IBM 370 Assembly Programming Discussion List
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This practice (LA 4,0(0,4)) is Not Recommended in these days of MVS/XA
and 31-bit addressing. On a 24-bit (MVS/370-mode) machine, this would
clear out the high byte (which has stuff put in it by the BALR
instruction - I've forgotten what, exactly, now). On a 31-bit machine,
it simply clears the high bit.

In the current case, it might not be so bad. But why the programmer
didn't just use LR R4,R15 / USING WHATNOT,R4 is beyond me. Perhaps
this is an entry into the Unclear Assembler contest? :-)

 --- Joe M.