Re: Possible fix for 30% performance regression in PR 33928

[Bradley Lucier <lucier at math dot purdue dot edu>]

On May 6, 2009, at 1:59 AM, Steven Bosscher wrote:

> And in any case, just adding back those functions doesn't explain why
> your code gets better. Blindly adding stuff back without understanding
> why that helps

I don't hesitate to admit a deep lack of understanding about the  
internals of gcc.  On the other hand, I do understand roughly the  
goals of "canonicalize address computations" and "choose the best  
addressing mode based on some cost", and that was why after some  
thought I added back precisely these two functions.

So, are there other places in the compiler that "canonicalize address  
computations" and/or "choose the best addressing mode based on some  
cost"?

> isn't going to get us anywhere closer to simplifying
> CSE.


> There was a reason to remove them: fwprop should do the same
> transformations already.


Good, there's a clear statement:  Are you saying that fwprop should  
perform what canon_for_address and find_best_addr were doing in the  
old CSE?

Brad