<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/57189>57189</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Unknown type name '__int64' errors inside the immintrin.h
        </td>
    </tr>

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

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

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

<pre>
    Inclusion of the intrin.h header, inside the private project caused compilation error, which reason was that the __int64 variable types used inside the immintrin.h weren't recognised by clang compiler. 

Clang compiler:
    -   Version: 13.0.1
    -   Target: x86_64-pc-windows-msvc
    -   Thread model: posix
OS:
    -   Windows 10 Enterprise

Error log:
`In file included from C:\Program Files\LLVM\lib\clang\13.0.1\include\x86intrin.h:15:
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:540:19: error: unknown type name '__int64'
static __inline__ __int64 __DEFAULT_FN_ATTRS
                  ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:541:35: error: unknown type name '__int64'
_InterlockedExchange64_HLEAcquire(__int64 volatile *_Target, __int64 _Value) {
                                  ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:541:62: error: unknown type name '__int64'
_InterlockedExchange64_HLEAcquire(__int64 volatile *_Target, __int64 _Value) {
                                                             ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:546:19: error: unknown type name '__int64'
static __inline__ __int64 __DEFAULT_FN_ATTRS
                  ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:547:35: error: unknown type name '__int64'
_InterlockedExchange64_HLERelease(__int64 volatile *_Target, __int64 _Value) {
                                  ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:547:62: error: unknown type name '__int64'
_InterlockedExchange64_HLERelease(__int64 volatile *_Target, __int64 _Value) {
                                                             ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:575:19: error: unknown type name '__int64'
static __inline__ __int64 __DEFAULT_FN_ATTRS
                  ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:576:42: error: unknown type name '__int64'
_InterlockedCompareExchange64_HLEAcquire(__int64 volatile *_Destination,
                                         ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:577:31: error: unknown type name '__int64'
                              __int64 _Exchange, __int64 _Comparand) {
                              ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:577:50: error: unknown type name '__int64'
                              __int64 _Exchange, __int64 _Comparand) {
                                                 ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:583:19: error: unknown type name '__int64'
static __inline__ __int64 __DEFAULT_FN_ATTRS
                  ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:584:42: error: unknown type name '__int64'
_InterlockedCompareExchange64_HLERelease(__int64 volatile *_Destination,
                                         ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:585:31: error: unknown type name '__int64'
                              __int64 _Exchange, __int64 _Comparand) {
                              ^
C:\Program Files\LLVM\lib\clang\13.0.1\include\immintrin.h:585:50: error: unknown type name '__int64'
                              __int64 _Exchange, __int64 _Comparand) {`
</pre>
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