From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 747593858413; Sat,  2 Apr 2022 13:55:30 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 747593858413
From: "andre.schackier at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/105136] New: [11/12] Missed optimization regression
 with 32-bit adds and shifts
Date: Sat, 02 Apr 2022 13:55:30 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: andre.schackier at gmail dot com
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-105136-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Sat, 02 Apr 2022 13:55:30 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105136

            Bug ID: 105136
           Summary: [11/12] Missed optimization regression with 32-bit
                    adds and shifts
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: andre.schackier at gmail dot com
  Target Milestone: ---

Given the following source code [godbolt](https://godbolt.org/z/daTxMYWKo)

#include <stdint.h>
int32_t foo(int64_t a, int32_t b, int cond) {
    if (cond) {
        a +=3D ((int64_t)b) << 32;
    }
    return a >> 32;
}

int32_t bar(int64_t a, int32_t b, int cond) {
    int32_t r =3D a >> 32;
    if (cond) {
        r +=3D b;
    }
    return r;
}

and compiling with "-O3" we get the following assembly:

foo:
        sal     rsi, 32
        mov     rax, rdi
        add     rax, rsi
        test    edx, edx
        cmove   rax, rdi
        shr     rax, 32
        ret
bar:
        sar     rdi, 32
        add     esi, edi
        test    edx, edx
        mov     eax, esi
        cmove   eax, edi
        ret

With gcc-10.3 we get for bar:
bar:
        sar     rdi, 32
        test    edx, edx
        lea     eax, [rsi+rdi]
        cmove   eax, edi
        ret

Also note that neither versions recognize that foo does the same as bar.

Credits: This was entirely found by Trevor Spiteri reported at the llvm-pro=
ject
here: https://github.com/llvm/llvm-project/issues/54718=