Re: Unsafe Optimizations (formerly Compiler Design in C...)

chip@tct.uucp (Chip Salzenberg)
Wed, 20 Jun 90 04:17:04 GMT

          From comp.compilers

Related articles
[6 earlier articles]
Re: Unsafe Optimizations (formerly Compiler Design in C...) MERRIMAN@ccavax.camb.com (George Merriman -- CCA/NY) (1990-06-15)
Re: Unsafe Optimizations (formerly Compiler Design in C...) holub@violet.Berkeley.EDU (1990-06-15)
Re: Unsafe Optimizations (formerly Compiler Design in C...) pardo@june.cs.washington.edu (1990-06-15)
Re: Unsafe Optimizations (formerly Compiler Design in C...) barmar@Think.COM (1990-06-15)
Re: Unsafe Optimizations (formerly Compiler Design in C...) henry@zoo.toronto.edu (1990-06-20)
Re: Unsafe Optimizations (formerly Compiler Design in C...) dan@kfw.com (1990-06-20)
Re: Unsafe Optimizations (formerly Compiler Design in C...) chip@tct.uucp (1990-06-20)
Re: Unsafe Optimizations (formerly Compiler Design in C...) grunwald@foobar.Colorado.EDU (Dirk Grunwald) (1990-06-20)
Re: Unsafe Optimizations (formerly Compiler Design in C...) marti@inf.ethz.ch (1990-06-21)
Re: Unsafe Optimizations (formerly Compiler Design in C...) pardo@june.cs.washington.edu (1990-06-21)
Re: Unsafe Optimizations (formerly Compiler Design in C...) kend%mrloog.wr.tek.com@RELAY.CS.NET (Ken Dickey) (1990-06-21)
Re: Unsafe Optimizations (formerly Compiler Design in C...) chittamu@dino.cs.umass.edu (1990-06-22)
Re: Unsafe Optimizations (formerly Compiler Design in C...) harrison@necssd.NEC.COM (1990-06-23)
| List of all articles for this month |

Newsgroups: comp.compilers
From: chip@tct.uucp (Chip Salzenberg)
References: <1990Jun12.163959.2593@esegue.segue.boston.ma.us> <1990Jun13.143951.2129@esegue.segue.boston.ma.us> <1990Jun15.051349.3016@esegue.segue.boston.ma.us>
Date: Wed, 20 Jun 90 04:17:04 GMT
Organization: ComDev/TCT, Sarasota, FL
Keywords: code, optimize

According to pardo@june.cs.washington.edu (David Keppel):
>[Two versions of strcpy() deleted]
>A moment's consideration should (hopefully) convince you that the
>first form requires two increments per iteration, while the latter
>requires only one.


But a moment's consideration convinced me that the first form requires
two array indexing operations, while the the latter requires none.


And besides, completely *safe* optimizations can transform either form
into the other. So there. :-)


--
Chip, the new t.b answer man <chip@tct.uucp>, <uunet!ateng!tct!chip>
--


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