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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/109907] Missed optimization for bit extraction (uses
 shift instead of single bit-test)
Date: Sat, 27 May 2023 04:02:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109907

--- Comment #28 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #26)
> (In reply to Andrew Pinski from comment #25)
> > Created attachment 55175 [details]
> > Patch which fixes `signed < 0`
> >=20
> > This patch improves comment #20 .
>=20
> Note this patch does not work for the case of normalizep =3D=3D -1 but I =
have a
> fix for that.

Also note this patch improves (a lot):
```
unsigned char f(long long t)
{
        return t < 0;
}
```
Down to:
```
f:
/* prologue: function */
/* frame size =3D 0 */
/* stack size =3D 0 */
.L__stack_usage =3D 0
        mov r24,r25
        rol r24
        clr r24
        rol r24
/* epilogue start */
        ret
```
Rather than what it was in GCC 13:
```
f:
        push r16
        ldi r16,lo8(63)
        rcall __lshrdi3
        mov r24,r18
pop r16
        ret
```=