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From: wallach@convexs.UUCP
Newsgroups: net.arch
Subject: Re: Right shift vs. divide
Message-ID: <3000002@convexs>
Date: Tue, 7-Jan-86 10:27:00 EST
Article-I.D.: convexs.3000002
Posted: Tue Jan  7 10:27:00 1986
Date-Received: Thu, 9-Jan-86 02:46:57 EST
References: <4772@alice.UUCP>
Lines: 17
Nf-ID: #R:alice.UUCP:4772:convexs:3000002:000:581
Nf-From: convexs.UUCP!wallach    Jan  7 09:27:00 1986


arithmetic right shifting is equivalent(numerically) to division if the
algorithm is implemented correctly.  just because most machines do it
wrong doesn't mean it doesn't work.  the correct algorithm for right
shifting for fixed point is:

1)if the operand is positive right shift.

2)if the operand is negative, negate the operand before shifting, then
right shift, and then negate the result.

if you want, try the infamous right shift all 1's (-1).

the division is round toward zero (ala fortran).

the MV series from data general perform arithmetic right shifting
correctly