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Path: utzoo!utcsri!greg
From: greg@utcsri.UUCP (Gregory Smith)
Newsgroups: comp.lang.c
Subject: Re: bit-field pointers / arrays
Message-ID: <3811@utcsri.UUCP>
Date: Fri, 19-Dec-86 14:31:19 EST
Article-I.D.: utcsri.3811
Posted: Fri Dec 19 14:31:19 1986
Date-Received: Fri, 19-Dec-86 23:22:36 EST
References: <2937@bu-cs.BU.EDU> <321@bms-at.UUCP>
Reply-To: greg@utcsri.UUCP (Gregory Smith)
Organization: CSRI, University of Toronto
Lines: 66
Summary:
In article <321@bms-at.UUCP> stuart@bms-at.UUCP (Stuart D. Gathman) writes:
> Unfortunately, a set of macros cannot use hardware bit-field
>instructions. Here is a list of processors which I know to have
>bit-field instructions that I can't get at from 'C':
...
> VAX
...
>it could not be *that* difficult. My complaint is that the macros do
>not utilize the hardware bitfield instructions. If your everyday optimizing
>compiler can figure out when to use these from a mess of shifts and masks,
>then I'll be satisfied. I think that bitfield arrays might be the easier
>approach, however.
Let's see:
main(){
int a,b,c,d;
register int x,y;
x = (a>>13) & 15; /* extract 4 bits */
b |= 1<>13) & 15; can't complain
ashl r10,$1,r0 | 1<