On Fri, Mar 07, 2025 at 01:04:10PM +0100, Jan Hubicka wrote:
> > diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
> > index fb93a6fdd0a..be5e27fc391 100644
> > --- a/gcc/config/i386/i386.cc
> > +++ b/gcc/config/i386/i386.cc
> > @@ -20600,12 +20600,26 @@ ix86_class_likely_spilled_p (reg_class_t rclass)
> > return false;
> > }
> >
> > -/* Implement TARGET_IRA_CALLEE_SAVED_REGISTER_COST_SCALE. */
> > +/* Implement TARGET_CALLEE_SAVE_COST. */
> >
> > static int
> > -ix86_ira_callee_saved_register_cost_scale (int)
> > -{
> > - return 1;
> > +ix86_callee_save_cost (spill_cost_type, unsigned int hard_regno,
> > machine_mode,
> > + unsigned int, int mem_cost, const HARD_REG_SET &, bool)
> > +{
> > + /* Account for the fact that push and pop are shorter and do their
> > + own allocation and deallocation. */
> > + if (GENERAL_REGNO_P (hard_regno))
> > + {
> > + /* push is 1 byte while typical spill is 4-5 bytes.
> > + ??? We probably should adjust size costs accordingly.
> > + Costs are relative to reg-reg move that has 2 bytes for 32bit
> > + and 3 bytes otherwise. Be sure that no cost table sets cost
> > + to 2, so we end up with 0. */
> > + if (mem_cost <= 2 || optimize_function_for_size_p (cfun))
> > + return 1;
> > + return mem_cost - 2;
> > + }
> > + return mem_cost;
>
> This is OK. In general, I think we could also go with assert on
> mem_cost <= 2, since that is kind of bogus setting (I don't think we
> will ever need to support x86 CPU with memory stores being as cheap as
> reg-reg moves), but current form is good.
Unless the loading/storing integer costs in x86-tune-costs.h are unrelated,
there are tons of tunings which have cost 2:
grep
'\(processor_costs\|2.*cost.of.loading.integer\|2.*cost.of.storing.integer\)'
x86-tune-costs.h
struct processor_costs ix86_size_cost = {/* costs for tuning for size */
{2, 2, 2}, /* cost of loading integer registers
{2, 2, 2}, /* cost of storing integer registers */
{2, 2, 2}, /* cost of loading integer registers
{2, 2, 2}, /* cost of storing integer registers */
struct processor_costs i386_cost = { /* 386 specific costs */
{2, 4, 2}, /* cost of loading integer registers
{2, 4, 2}, /* cost of storing integer registers */
{2, 4, 2}, /* cost of loading integer registers
{2, 4, 2}, /* cost of storing integer registers */
struct processor_costs i486_cost = { /* 486 specific costs */
{2, 4, 2}, /* cost of loading integer registers
{2, 4, 2}, /* cost of storing integer registers */
{2, 4, 2}, /* cost of loading integer registers
{2, 4, 2}, /* cost of storing integer registers */
struct processor_costs pentium_cost = {
{2, 4, 2}, /* cost of loading integer registers
{2, 4, 2}, /* cost of storing integer registers */
{2, 4, 2}, /* cost of loading integer registers
{2, 4, 2}, /* cost of storing integer registers */
struct processor_costs lakemont_cost = {
{2, 4, 2}, /* cost of loading integer registers
{2, 4, 2}, /* cost of storing integer registers */
{2, 4, 2}, /* cost of loading integer registers
{2, 4, 2}, /* cost of storing integer registers */
struct processor_costs pentiumpro_cost = {
{2, 2, 2}, /* cost of storing integer registers */
{2, 2, 2}, /* cost of storing integer registers */
struct processor_costs geode_cost = {
{2, 2, 2}, /* cost of loading integer registers
{2, 2, 2}, /* cost of storing integer registers */
{2, 2, 2}, /* cost of loading integer registers
{2, 2, 2}, /* cost of storing integer registers */
struct processor_costs k6_cost = {
{2, 3, 2}, /* cost of storing integer registers */
{2, 3, 2}, /* cost of storing integer registers */
struct processor_costs pentium4_cost = {
{2, 3, 2}, /* cost of storing integer registers */
{2, 3, 2}, /* cost of storing integer registers */
Jakub
