Path: utzoo!attcan!uunet!cs.utexas.edu!samsung!xylogics!transfer!lectroid!bigbootay!dswartz
From: dswartz@bigbootay.sw.stratus.com (Dan Swartzendruber)
Newsgroups: comp.arch
Subject: Re: unexpected CPU behavior [was 486 bugs -- it's in there!]
Message-ID: <1429@lectroid.sw.stratus.com>
Date: 30 May 90 18:18:05 GMT
References: <1990May27.110726.17007@xavax.com> <16744@haddock.ima.isc.com> <2159@sauron.Columbia.NCR.COM>
Sender: usenet@lectroid.sw.stratus.com
Reply-To: dswartz@bigbootay.sw.stratus.com (Dan Swartzendruber)
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Organization: Stratus Computer, Software Engineering.
Lines: 17

I don't quite understand your comment: "...C compilers seem to
keep doing this..."  Please satisfy my naive curiosity.  What is
wrong with "*p = 0;" generating a "clr (a0)" or somesuch.  When
you have an instruction which is defined a zeroing its operand,
this seems a rather obvious use to me!  If the original microcoders
made a silly mistake by sharing the single-operand RMW microcode
for this instruction without documenting it (and BTW, I do have an
OLD manual where the footnote is missing from the clr page.), that
is hardly grounds for slandering C compiler writers who expected the
instruction to work as documented.  Do you feel that it is more
intuitive to declare a variable whose sole purpose is to be zeroed
and then assigned to the destination???


--

Dan S.