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Re: Missed optimizations: Constant propagation / algebraic simplification re-run after after reload.?
- From: Andrew Pinski <pinskia at physics dot uc dot edu>
- To: bjoern dot m dot haase at web dot de (Björn Haase)
- Cc: gcc at gcc dot gnu dot org
- Date: Fri, 6 May 2005 16:18:11 -0400 (EDT)
- Subject: Re: Missed optimizations: Constant propagation / algebraic simplification re-run after after reload.?
>
> Hello,
>
> when working on the AVR target I stepped over the follwoing issue (IMO not
> urgent but still bearing quite some potential of improvement):
>
> When implementing "lowering" of SImode and HImode expressions to QImode
> sequences by splitters after reload, quite a number of new optimization
> opportunities show up that presently are not realized. These would probably
> require that some kind of constant propagation and algebraic simplification
> would be re-run *after* reload.
> A typical case are mixed-mode expressions like in the function
>
> uint16_t
> dummy (uint8_t y, uint32_t x)
> {
> return x & y;
> }
You should expand this at expand time instead as there are enough optimizations
before expand time to get to it optimized.
-- pinski