<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/114626>114626</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            clang multiarch is broken (at least on macOS)
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          alecazam
      </td>
    </tr>
</table>

<pre>
    So macoOS clang seems to have left out multiarch support for precompiled headers.   So I split out our arch specifications as such, and compiled each pch for each arch.

CXXARCH := -arch x86_64 -mavx2 -mf16c -mfma \
 -arch arm64

The problem is now I need to pass the pch to the compiles.  This requires use of -include-pch like so.

PRECOMPILED_CXXFLAGS += \
        -include-pch $(PRECOMPILED_PCH_ARM)\
         -include-pch $(PRECOMPILED_PCH_X64)\

But that doesn't work since it tries to link the x64 pch to the .o.   So then I try -Xarch

PRECOMPILED_CXXFLAGS += \
  -Xarch_arm64 -include-pch  $(PRECOMPILED_PCH_ARM)\
 -Xarch_x86_64 -include-pch  $(PRECOMPILED_PCH_X64)\

That generates the following failure:
invalid Xarch argument: '-Xarch_arm64 -include-pch', options requiring arguments are unsupported
  
So I have no idea how to fix this.  The -Xarch limitation is very limiting.


</pre>
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