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    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - "Function marked read-only and write-only" assertion at -O1"
   href="https://bugs.llvm.org/show_bug.cgi?id=41391">41391</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>"Function marked read-only and write-only" assertion at -O1
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>libraries
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>Interprocedural Optimizations
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>luke.lau@intel.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Using clang to compile the following C code at -O1:

```
int i = 0;
void foo();
void bar() { if (!i) foo(); }
void foo() { i = 1; bar(); }
```

<span class="quote">> clang -O1 test.c</span >

... clang-8: llvm-project/llvm/lib/Transforms/IPO/FunctionAttrs.cpp:263: bool
addReadAttrs(const (anonymous namespace)::SCCNodeSet &, AARGetterT &&)
[AARGetterT = llvm::LegacyAARGetter &]: Assertion `!(ReadsMemory &&
WritesMemory) && "Function marked read-only and write-only"' failed.


<span class="quote">> clang -v</span >

clang version 9.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
31e4fec3c021b21eae8cb7b26691632716c1e3cc)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/luke/Source/llvm-project/build/./bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Candidate multilib: .;@m64
Selected multilib: .;@m64</pre>
        </div>
      </p>


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