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Re: Re-run of loop pass
- To: Michael Hayes <m dot hayes at elec dot canterbury dot ac dot nz>
- Subject: Re: Re-run of loop pass
- From: Jeffrey A Law <law at cygnus dot com>
- Date: Sun, 18 Oct 1998 01:14:51 -0600
- cc: egcs at cygnus dot com
- Reply-To: law at cygnus dot com
In message <13865.9178.455954.70561@ongaonga.elec.canterbury.ac.nz>you write:
> I've noticed that this can generate poorer code when unrolling loops
> or using the bct optimisation if a BIV is eliminated on the first
> pass.
>
> On the second pass, loop_iterations is often unable to determine the
> iteration count for loops with limits that should be able to be
> determined at compile time. Loop unrolling or the bct optimisation
> then makes a dog's breakfast of things.
We've generally gotten better code.
You should investigate why the second loop pass is unable to determine
loop iteration counts.
jeff