[clang] [X86] Add MMX/SSE/AVX PHADD/SUB & HADDPS/D intrinsics to be used in constexpr (PR #156822)

[Simon Pilgrim via cfe-commits]

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@@ -19,6 +20,7 @@
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/SipHash.h"
+#include <cassert>
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RKSimon wrote:

unnecessary?

https://github.com/llvm/llvm-project/pull/156822