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From: firth@sei.cmu.edu (Robert Firth)
Newsgroups: comp.arch
Subject: Re: Optimization vs. the programmer
Message-ID: <919@aw.sei.cmu.edu.sei.cmu.edu>
Date: Mon, 13-Apr-87 08:24:20 EST
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Posted: Mon Apr 13 08:24:20 1987
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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).

Oh.  I thought strength reduction was replacing i := j*8 by i := i+8
within a loop whose induction variable was j.  So it's explained in
Wulf's The Design of an Optimising Compiler, anyway.

Also, don't you mean "j&7" in the second replacement?  And in the
first, the replacement is invalid if the expression overflows.