[clang] [Headers][X86] VectorExprEvaluator::VisitCallExpr - allow SSE/AVX2/AVX512 pack intrinsics to be used in constexpr (PR #156003)

[Simon Pilgrim via cfe-commits]

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@@ -11575,6 +11575,43 @@ static bool handleVectorElementCast(EvalInfo &Info, const FPOptions FPO,
   return false;
 }
 
+static bool
+evalPackBuiltin(const CallExpr *E, EvalInfo &Info, APValue &Result,
+                llvm::function_ref<APSInt(const APSInt &)> narrowElement) {
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RKSimon wrote:

narrowElement -> PackFn

https://github.com/llvm/llvm-project/pull/156003