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Re: PowerPC reusing CTR register for nested loops
- To: law at cygnus dot com
- Subject: Re: PowerPC reusing CTR register for nested loops
- From: David Edelsohn <dje at watson dot ibm dot com>
- Date: Fri, 11 Sep 1998 14:48:45 -0400
- Cc: egcs-bugs at cygnus dot com
>>>>> Jeffrey A Law writes:
Jeff> Could be that we run loop opts twice now. That's the only thing that
Jeff> immediately comes to mind.
Yes, that turns out to be the problem. Re-running loop_optimize()
clears out the scoreboard of CTR in use. On the second pass it again
tries to utilize the CTR register on a loop that it discarded on the
previous pass because the regsiter was in use. Of course with a blank
slate, it succeeds this time.
I am going to pass in an additional flag to loop_optimize() to
avoid calling the BCT optimization during the "rerun" first time through
and see if things now work.
David