Hi Richard, Thanks for your comments. 在 2024/5/10 15:16, Richard Biener 写道: > But if targets return sth < COSTS_N_INSNS (1) but > 0 this is now no > longer meaningful. So shouldn't it instead be > > return cost > 0 ? cost : 1; Yes, it's better.
> > ? Alternatively returning fractions of COSTS_N_INSNS (1) from set_src_cost > is invalid and thus the target is at fault (I do think that making zero the > unknown value is quite bad since that makes it impossible to have zero > as cost represented). > > It seems the check is to aovid pattern_cost return zero (unknown), so the > comment holds to pattern_cost the same (it returns an 'int' so the better > exceptional value would have been -1, avoiding the compare). But sometime it adds an insn cost. If the unknown cost is -1, the total cost might be distorted. > > Richard. Thanks Gui Haochen
