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From: bright@Data-IO.COM (Walter Bright)
Newsgroups: comp.lang.c,comp.arch
Subject: What is loop unfolding
Message-ID: <1686@dataio.Data-IO.COM>
Date: 8 Sep 88 18:01:25 GMT
References: <5612@june.cs.washington.edu> <3010@wright.mips.COM> <403@marob.MASA.COM>
Reply-To: bright@dataio.Data-IO.COM (Walter Bright)
Organization: Data I/O Corporation; Redmond, WA
Lines: 17

In article <403@marob.MASA.COM> samperi@marob.masa.com (Dominick Samperi) writes:
>Sorry for jumping into this discussion rather late, but could someone
>please give a brief definition of "loop unrolling."

It is the conversion of loops like:
	for (i = 0; i < 2; i++)
	    foo(i);
into:
	i = 0; foo(i);
	i = 1; foo(i);
	i = 2;
Constant propagation and dead assignment elimination is then done in an
attempt to reduce the above to:
	foo(0);
	foo(1);

Note: my optimizer does not do loop unrolling. Loop unrolling is, however,
common among Fortran optimizers.