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From: "xry111 at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/111334] [14 regression] ICE is reported during the
 combine pass optimization
Date: Fri, 08 Sep 2023 07:16:46 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111334

--- Comment #15 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to chenglulu from comment #13)
> (In reply to Xi Ruoyao from comment #12)
> > (In reply to chenglulu from comment #11)
> > > (In reply to Xi Ruoyao from comment #10)
> > > > (In reply to Xi Ruoyao from comment #9)
> > > >=20
> > > > >  (define_insn "<optab>di3_fake"
> > > > >    [(set (match_operand:DI 0 "register_operand" "=3Dr,&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)))]
> > > >=20
> > > > With this the compiler will still believe all bad {div,mod}.w{,u}
> > >=20
> > > I think this is already defined as UNSPEC. Isn=E2=80=99t the simpler =
the logic, the
> > > better?
> >=20
> > Yes, I think we should just use 4 different UNSPEC_ values and the simp=
le
> > version.  But I've not find a way to use 4 different UNSPEC_ values in =
the
> > RTL template except duplicating everything 4 times...
>=20
> I still have a question that I don't quite understand, that is, why that =
the
> four generated strings are equivalent when using an UNSPEC name? My templ=
ate
> names are different, and they will not be automatically matched during
> optimization.???

Oh I get it, you mean

 (define_insn "<optab>di3_fake"
   [(set (match_operand:DI 0 "register_operand" "=3Dr,&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"))))]
+         (unspec:DI [(any_div:DI
+                       (match_operand:DI 1 "register_operand" "r,r,0")
+                       (match_operand:DI 2 "register_operand" "r,r,r"))]
+                    UNSPEC_ANY_DIV)))]
   ""
 {
   return loongarch_output_division ("<insn>.w<u>\t%0,%1,%2", operands);

Good idea! I think it's better than my stupid hacks :).

I'd been thinking about:

 (define_insn "<optab>di3_fake"
   [(set (match_operand:DI 0 "register_operand" "=3Dr,&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"))))]
+         (unspec:DI [(match_operand:DI 1 "register_operand" "r,r,0")
+                     (match_operand:DI 2 "register_operand" "r,r,r")]
+                    UNSPEC_ANY_DIV)))]
   ""
 {
   return loongarch_output_division ("<insn>.w<u>\t%0,%1,%2", operands);

and this is just wrong.=