[LLVMdev] Question about FMA formation

[Michael Ilseman]

Right now we're shying towards having a re-association helper in codegen-prepare that will re-associate expressions (if allowed). This would allow fast-isel to more easily spot FMA opportunities, and form better code.

On Dec 12, 2012, at 5:11 PM, Eric Christopher <echristo at gmail.com> wrote:

> 
> 
> 
> You hit send right when I did!
> For your example, do you mean that it's grouped like:
> (fadd (fadd (fmul a b) (fmul c d)) e)
> 
> How would your pass go about handling these patterns and is that something that would be too complicated for fast-isel to do on the fly?
> 
> 
> Depends on how they're grouped, but if the formation happens prior to codegen then fast-isel will just handle whatever new instruction you've got. An example of IR would be useful though :)
> 
> -eric

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