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Re: Multiple cse and loop opts
- To: Kent Vander Velden <graphix at iastate dot edu>
- Subject: Re: Multiple cse and loop opts
- From: Jeffrey A Law <law at hurl dot cygnus dot com>
- Date: Tue, 12 Jan 1999 01:12:00 -0700
- cc: egcs at egcs dot cygnus dot com
- Reply-To: law at cygnus dot com
In message <199901110429.WAA30945@isua5.iastate.edu>you write:
> That seems to be the case. I ran a version of cc1 and cc1plus over some
> more sane code and saw _very_ little improvement. It was meant as more of
> a test to see if I could get the two loops to come out with the same
> assembly.
OK.
> I can try to look at this especially if someone could suggest a good
> starting approach. The rtl for the two loops should be very
> similar after the first CSE, I suspect.
Yes. I'm kind of suprised that neither cse nor the jump pass after cse
removed the switch with no real body. I believe both passes have the
capability of doing this.
> What I do not quite understand is if the body of a loop is removed
> why not remove the loop itself as well?
What exactly are you referring to? I believe when the body of a loop is
removed we may keep the notes around, which is dubious. Nobody's gotten
around to seeing if deleting those notes is safe and profitable yet.
jeff