https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112935
--- Comment #8 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #7)
> (In reply to Xi Ruoyao from comment #5)
> >
> > so we still slightly penalty multiplication. To me we should code
> > COSTS_N_INSNS (1) + 1 into loongarch_rtx_cost_optimize_size instead of
> > special casing it in loongarch_rtx_costs.
>
> Oh yes slightly penalty is definitely not going make a huge difference if
> the cost of an mult instruction is worse than an and and an neg.
>
> >
> > For the default value (used when -O2) I'll do some micro-benchmark...
I've changed it to
/* Default RTX cost initializer. */
loongarch_rtx_cost_data::loongarch_rtx_cost_data ()
: fp_add (COSTS_N_INSNS (5)),
fp_mult_sf (COSTS_N_INSNS (5)),
fp_mult_df (COSTS_N_INSNS (5)),
fp_div_sf (COSTS_N_INSNS (8)),
fp_div_df (COSTS_N_INSNS (8)),
int_mult_si (COSTS_N_INSNS (4)),
int_mult_di (COSTS_N_INSNS (4)),
int_div_si (COSTS_N_INSNS (5)),
int_div_di (COSTS_N_INSNS (5)),
branch_cost (6),
memory_latency (4) {}
based on micro-benchmark results. This fixes the int * _Bool case and int * 17
case. But for the original test case I still get a multiplication instruction.
