[PATCH] Loop Strength Reduce: Scaling factor cost.

[Andrew Trick]

On May 31, 2013, at 11:11 AM, Quentin Colombet <qcolombet at apple.com> wrote:

> Hi,
> 
> Scaling factor are often used within loops to access cells of an array.
> When applying a scaling factor is not free, the scaling factor should be part of the induction variable, i.e., hoisted outside the loop.
> 
> I have attached a patch that accounts for the cost of scaling factor in Loop Strength Reduce when rating the formulae (with the proper target hook).
> 
> The default implementation of the hook is: if the addressing mode is legal, the scaling factor is free.
> This keeps the current behavior of LSR. We can then improve this, target by target, by overloading the target hook accordingly.
> 
> Thanks for the review,
> 
> -Quentin

LGTM.
-Andy

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