Redundant logical operations left after early splitting

[hutchinsonandy@aim.com]

Paolo

I placed extra fwprop before local-alloc as this was just  before NOP 
got created and after splitting.

Putting fwprop after combine is no problem - but is too early - none of 
the patterns would be split at that time - preventing byte level 
propagations.

As register usage as well as code size is clearly relevant here, 
effective propagation before reload is the most desirable.

(PS I was impressed by fwprop code, I actually stand a chance of 
understanding some of it)

best regards




-----Original Message-----
From: Paolo Bonzini <bonzini@gnu.org>
To: Andy H <hutchinsonandy@aim.com>; GCC Development <gcc@gcc.gnu.org>
Sent: Thu, 21 Feb 2008 1:06 am
Subject: Re: Redundant logical operations left after early splitting


> This would indicate that simplify-rtx inside fwprop is removing OR 
Rx,0 
> but not picking up the the additionally revealed forward propagation 
> oppertunities 
> This would seem to be an avoidable limitation. 
 
Yes, can you send me your MD patch and a simple testcase? fwprop is 
supposed to be "cascading", and some bugs in cascading were already 
revealed by the AVR port. 
 
It might be even more worthwhile to try *moving* fwprop2 after combine, 
then. 
 
Paolo 


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