ICM vs. L and LTR

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1 total messages Started by "Dwayne A. Blumenberg" Wed, 12 Aug 1992 16:37

#321

Author: "Dwayne A. Blumenberg"
Date: Wed, 12 Aug 1992 16:37

28 lines
1418 bytes

I've noticed lately that some recent IBM code uses
the sequence:

    L     Rx,AREA
    LTR   Rx,Rx
    BNZ   SOMEWHERE

and I was wondering if

    ICM   Rx,15,AREA
    BNZ   SOMEWHERE

would be faster?  It looks to me like the two code segments
would produce identical results (ignoring for the moment that
the LOAD instruction could take an index register, and that
ICM wasn't available on the 360, and that LOAD on a 360 could
cause a specification exception).

I'm sure that LTR is very fast, but is L + LTR faster than
ICM?  What, if any, advantages does the L + LTR sequence offer
above ICM?

Thanks.
--
Dwayne A. Blumenberg            | Internet:  dwayne@dwayneb.b30.ingr.com
IBM Systems Programmer          | UUCP:      ...uunet!ingr!b30!dwayneb!dwayne
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