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From: "zhongyunde at huawei dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/107190] New: [aarch64] regression with optimization
 -fexpensive-optimizations
Date: Sun, 09 Oct 2022 10:33:16 +0000
X-Bugzilla-Reason: CC
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 13.0
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: zhongyunde at huawei dot com
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107190

            Bug ID: 107190
           Summary: [aarch64] regression with optimization
                    -fexpensive-optimizations
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhongyunde at huawei dot com
  Target Milestone: ---

This case is simplify from https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D1=
07090,
and we can see that the codegen of function `test_m` has some regression wi=
th
optimization -fexpensive-optimizations, https://gcc.godbolt.org/z/zbKrEox4j

This is because the pass 208t.widening_mul is controlled by
-fexpensive-optimizations (default on at -O3), it conversion

```
  m_12 =3D m_9 + m1_10;
  if (m1_10 > m_12)
```
into

```
  _17 =3D .ADD_OVERFLOW (m_9, m1_10);
  m_12 =3D REALPART_EXPR <_17>;
  _18 =3D IMAGPART_EXPR <_17>;
  if (_18 !=3D 0)``

```=