Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!rutgers!ames!amdahl!drivax!tyler
From: tyler@drivax.UUCP (William Tyler)
Newsgroups: comp.arch
Subject: Re: 32-bit CPUs ( NEC V70 ) and silly examples
Message-ID: <1526@drivax.UUCP>
Date: Mon, 11-May-87 14:38:55 EDT
Article-I.D.: drivax.1526
Posted: Mon May 11 14:38:55 1987
Date-Received: Sat, 16-May-87 01:33:52 EDT
References: <3810030@nucsrl.UUCP> <491@necis.UUCP> <3530@spool.WISC.EDU> <4016@necntc.NEC.COM> <162@auvax.UUCP>
Reply-To: tyler@drivax.UUCP (William Tyler)
Followup-To: comp.arch
Distribution: na
Organization: Digital Research, Monterey
Lines: 29
Keywords: V60, V70, not so silly examples
Summary: Not so silly

In article <162@auvax.UUCP> rwa@auvax.UUCP (Ross Alexander) criticizes the
following example C code & V60/V70 implementation as being contrived.

 >> 		_______________________________________________
 >> 		| struct sttyp {
 >> 		|	unsigned first, second, third;
 >> 		|	struct sttyp *fourth;
 >> 		|	double fifth, a,b,c,d,e;} *stru
 >> C code:	|
 >> 		|
 >> 		| stru->fourth->fourth->third = 2;
 >> 		|==============================================
 >> 		| mov.w _stru+0xc,r0	# &(stru->fourth) in R0
 >> Assembly:	|
 >> 		| mov.w #2,0x8[0xc[r0]]	# stru->fourth->
 >> 		|			#    fourth->third = 2;
 >> 		|______________________________________________


In programs dealing with complex data structures, this sort of construction 
comes up fairly often.  Just as an exercise, I used egrep on one modest sized
(about 1K lines) C program of mine that deals primarily with data structure
manipulation.  I came up with 2 pages of lines that contained '->' at least
three times, most of them in constructs roughly equivalent to the example
above.  In the context of the application, the usages were not contrived, 
nor were they particularly difficult to understand.  
-- 

Bill Tyler ... {seismo,hplabs,sun,ihnp4}!amdahl!drivax!tyler