Path: utzoo!mnetor!uunet!husc6!hao!noao!mcdsun!fnf
From: fnf@mcdsun.UUCP (Fred Fish)
Newsgroups: comp.arch
Subject: Re: taken -vs- untaken branches
Message-ID: <637@mcdsun.UUCP>
Date: 11 Jan 88 18:22:11 GMT
References: <496@cresswell.quintus.UUCP> <638@l.cc.purdue.edu> <20339@amdahl.amdahl.com> <588@PT.CS.CMU.EDU>
Reply-To: fnf@mcdsun.UUCP (Fred Fish)
Organization: Motorola Microcomputer Division
Lines: 31

In article <588@PT.CS.CMU.EDU> lindsay@K.GP.CS.CMU.EDU (Donald Lindsay) writes:
>In article <20339@amdahl.amdahl.com> chuck@amdahl.amdahl.com (Charles Simmons) writes:
>>One method of allowing a compiler to automagically guess whether
>>a branch will usually be taken or not, would be ...
>
>The best heuristics use high-level context.  For example, a loop construct
>is liable go around again. An IF-part is more likely to be executed than an
>ELSE part.

I'm not so sure about the above generalization, it probably has a lot to
do with individual style.  For example, I almost always tend to write
code with the following if(){}else{} style:

	if (<what I expected to happen didn't happen>) {
		<take some sort of short evasive action>
	} else {
		<begin long sequence of instructions>
		.
		.
		.
		<end long sequence of instructions>
	}

Thus the above generalization would be almost always 100% wrong for my
style, unless lots of unexpected things happened to me...

-Fred

-- 
# Fred Fish    hao!noao!mcdsun!fnf    (602) 438-3614
# Motorola Computer Division, 2900 S. Diablo Way, Tempe, Az 85282  USA