> I imagine doing it in reverse postorder would still make sense. > > But my point was that, for the current fwprop limitation of substituting > into exactly one use of a register, we can check whether that use is > the *only* use of register. > > I.e. if we substitute: > > A: (set (reg R1) (foo (reg R2))) > > into: > > B: (set ... (reg R1) ...) > > if R1 and R2 are likely to be in the same register class, and if B > is the only user of R2, then we don't need to calculate register > pressure. The change is either neutral (if R2 died in A) or an > improvement (if R2 doesn't die in A, and so R1 and R2 were previously > live at the same time).
Ah, understood, thanks. Sure, that one I can include. Regards Robin
