https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111334
--- Comment #10 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to Xi Ruoyao from comment #9)
> (define_insn "<optab>di3_fake"
> [(set (match_operand:DI 0 "register_operand" "=r,&r,&r")
> - (sign_extend:DI
> - (any_div:SI (match_operand:DI 1 "register_operand" "r,r,0")
> - (match_operand:DI 2 "register_operand" "r,r,r"))))]
> - ""
> + (if_then_else
> + (and (eq (match_operand:DI 1 "register_operand" "r,r,0")
> + (sign_extend:DI (subreg:SI (match_dup 1) 0)))
> + (eq (match_operand:DI 2 "register_operand" "r,r,r")
> + (sign_extend:DI (subreg:SI (match_dup 2) 0))))
> + (sign_extend:DI
> + (any_div:SI (subreg:SI (match_dup 1) 0)
> + (subreg:SI (match_dup 2) 0)))
> + (unspec:DI [(const_int 0)] UNSPEC_BAD_DIVW)))]
With this the compiler will still believe all bad {div,mod}.w{,u} instructions
generate the exactly same unspecified value. But I don't think this is really
relevant: if a program depends on the unspecified value (no matter one value or
multiple values) it's already wrong.
If we are really "paranoid" about this we can make 4 UNSPEC_BAD_* constants and
use [(match_dup 1) (match_dup 2)] instead of [(const_int 0)].
> + "TARGET_64BIT"
> {
> return loongarch_output_division ("<insn>.w<u>\t%0,%1,%2", operands);
> }
