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



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


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