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From: desj@brahms.UUCP
Newsgroups: comp.arch
Subject: Re: Optimization vs. the programmer
Message-ID: <3135@jade.BERKELEY.EDU>
Date: Sat, 11-Apr-87 17:24:04 EST
Article-I.D.: jade.3135
Posted: Sat Apr 11 17:24:04 1987
Date-Received: Sun, 12-Apr-87 19:49:25 EST
References: <479@danews.ATT.COM> <3300003@uiucdcsm>
Sender: usenet@jade.BERKELEY.EDU
Reply-To: desj@brahms.Berkeley.EDU (David desJardins)
Organization: UC Berkeley Math Dept [IN EXILE]
Lines: 11

In article <3300003@uiucdcsm> grunwald@uiucdcsm.cs.uiuc.edu writes:
>
>Strength reduction is replacement of operations such as "i = j * 8" by
>"i = j << 3", or "i = j % 8" by "i = j & 0x3" (if j is unsigned).
                                  ^^^^^^^^^^^   ^^^^^^^^^^^^^^^^
   I'm sure you mean "i = j & 0x7".  But, more importantly, this is the
right remainder to compute even if j is signed (assuming two's-complement,
of course).  It's too bad more people (especially hardware designers!)
don't realize this.

   -- David desJardins