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      <base href="https://llvm.org/bugs/" />
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - Itanium non-virtual value parameter calling conventions incorrect for non-trivially move-able types."
   href="https://llvm.org/bugs/show_bug.cgi?id=28593">28593</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Itanium non-virtual value parameter calling conventions incorrect for non-trivially move-able types.
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

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

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

        <tr>
          <th>OS</th>
          <td>Windows NT
          </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>-New Bugs
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>eric@efcs.ca
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>3.1.1[value.parameters] of the Itanium spec states:

<span class="quote">> In the special case where the parameter type has a non-trivial copy 
> constructor or destructor, the caller must allocate space for a temporary 
> copy, and pass the resulting copy by reference</span >

Currently clang only considers copy constructors and not move constructors when
deciding on the calling convention, Meaning types with non-trivial move
constructors are not passed in allocated space.

GCC 

For example:

struct Foo {
  Foo() {}
  Foo(Foo const&) = default;
  Foo(Foo&&);
};

int foo(Foo);
void bar() { foo(Foo{}); }
// generates the assembly:
// bar(): jmp foo

Possibly related to <a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - Deleted copy constructor, value parameter & move cause incorrect results"
   href="show_bug.cgi?id=20799">https://llvm.org/bugs/show_bug.cgi?id=20799</a></pre>
        </div>
      </p>
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