All, The DIV/MOD expansion performed in expmed is basically driven by RTX costs/-Os that are provided by the backend.In a few instances these costs and or _os appear to be ignored. One senerio is divsion by a constant in a mode whose size <= HOST_BITS_PER_WIDE_INT it will always expand the DIV/MOD using multiplation (Montgomery) when optimizing for size. Shouldn't this expansion be be guarded by !speed and the expansion skipped allowing the backend open coding an DIV/MOD sequence or libcall. Is guarding this with a !speed guard the best thing to do for most backends or should this be controlled with a new target hook with the default hook returning true for yes expand maintaining the status quo giving the backends to override. Another senerio is signed divison of a power-of-2 if the backend dosn't have optabs for sdiv and sdivmod then expand_sdiv_pow2 will be choosen even if otimizing for size and sdiv_pow2_cheap() retuns true! if (sdiv_pow2_cheap (speed, compute_mode) && ((optab_handler (sdiv_optab, compute_mode) != CODE_FOR_nothing) || (optab_handler (sdivmod_optab, compute_mode) != CODE_FOR_nothing))) quotient = expand_divmod (0, TRUNC_DIV_EXPR, compute_mode, op0, gen_int_mode (abs_d, compute_mode), NULL_RTX, 0); else quotient = expand_sdiv_pow2 (compute_mode, op0, abs_d); When optimizing for size (!speed) and sdiv_pow2_cheap() is true we ideally don't want to use expand_sdiv_pow2 but instead let the back end opend code the DIV. Question how can one determine if a backend can open code a DIV/MOD Graham
