Re: Machine dependent Tree optimization?

[Ian Lance Taylor <iant at google dot com>]

"Bingfeng Mei" <bmei@broadcom.com> writes:

> Of couse, for processors without long/short instructions, this copy
> propagation is benefiical for performance by reducing unnecessary
> dependency. Therefore, whether to apply this copy propagation is machine
> dependent to some degree.  
> 
> What I do now is to add some check in tree-ssa-copy.c and tree-ssa-dom.c
> for our target. But this is not very clean. My question is whether there
> is better way to implement such machine-dependent tree-level
> optimization (like hooks in RTL level).  I believe there are other
> processors that have the similar problem. What is common solution? 

This should normally be done at the RTL level by making long constants
more expensive in RTX_COSTS.  With luck that will let gcse pick this
up.

Ian