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Re: Loop unrolling
- To: Lee Iverson <leei at ai dot sri dot com>
- Subject: Re: Loop unrolling
- From: Jeffrey A Law <law at cygnus dot com>
- Date: Tue, 02 Jun 1998 01:32:28 -0600
- cc: Stephen Williams <steve at icarus dot icarus dot com>, Gerald Pfeifer <pfeifer at dbai dot tuwien dot ac dot at>, egcs at cygnus dot com
- Reply-To: law at cygnus dot com
> As is stands now, deleting empty loops is a very desirable *feature*,
> especially for higher-level languages like C++ and Java which may just
> generate loops that the programmer doesn't see. If anything, we need
> to expand the detection and deletion of empty loops. A couple of us
> embarked on this exercise for a couple of weeks last summer, but the
> lack of register lifetime information in the loop optimization pass
> bit us badly. Maybe its time to resurrect this old code and make it
> work?
If you can provide source examples which show C++ & Java creating empty
loops behind the programmer's back it would go a long way to convincing
everyone that eliminating empty loops is a good idea.
It's also been suggested that having register lifetime information would
allow us to fix the infamous x86 strength reduction bug and re-enable
strength reduction.
jeff