Hello, > "Linthicum, Tony" <[EMAIL PROTECTED]> writes: > > > * Would using a tree-level API like estimate_num_insns be superior > > to using a simple cost of 1 per statment? > > For this sort of calculation, I would guess not. I would imagine that > on most processors the cost of a single vector instruction is > comparable to the cost of the same operation on scalar operands. So > simply counting instructions should give you a good indication of > whether vectorization is profitable, even though each instruction will > of course have a different cost. > > If this turns out not to be the case, then I think the next step would > be to have a target defined multiplier for vector instructions, > indicating that for that target vector instructions were more or less > expensive than scalar instructions according to some ratio. > > I doubt that using the full fledged cost infrastructure would give you > better results than that in practice.
on the other hand, using it does not cost you anything, and would avoid risk of creating yet another code duplication. > > * What is the best way to access target level cost information? > > I'm sure you know that the loop code does this by generating RTL and > asking for the cost of it (computation_cost in tree-ssa-loop-ivopts.c). Which should be removed (I have some patches for that, but I somehow forgot on them because of other issues). Zdenek
