On Fri, Oct 28, 2022 at 2:34 PM Segher Boessenkool
<[email protected]> wrote:
>
> On Wed, Oct 26, 2022 at 11:58:57AM -0700, H.J. Lu via Gcc-patches wrote:
> > In i386.md, neg patterns which set MODE_CC register like
> >
> > (set (reg:CCC FLAGS_REG)
> > (ne:CCC (match_operand:SWI48 1 "general_reg_operand") (const_int 0)))
> >
> > can lead to errors when operand 1 is a constant value. If FLAGS_REG in
>
> But it cannot be. general_reg_operand will not allow that:
> ===
> (define_predicate "general_reg_operand"
> (and (match_code "reg")
> (match_test "GENERAL_REGNO_P (REGNO (op))")))
> ===
>
> > (set (reg:CCC FLAGS_REG)
> > (ne:CCC (const_int 2) (const_int 0)))
> >
> > is set to 1, RTX simplifiers may simplify
>
Here is another example:
(define_insn "*neg<mode>_ccc_1"
[(set (reg:CCC FLAGS_REG)
(ne:CCC
(match_operand:SWI 1 "nonimmediate_operand" "0")
(const_int 0)))
(set (match_operand:SWI 0 "nonimmediate_operand" "=<r>m")
(neg:SWI (match_dup 1)))]
""
"neg{<imodesuffix>}\t%0"
[(set_attr "type" "negnot")
(set_attr "mode" "<MODE>")])
Operand 1 can be a known value.
H.J.
