[clang] [clang] Constexpr for __builtin_shufflevector and __builtin_convertvector (PR #76615)

[Simon Pilgrim via cfe-commits]

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@@ -10895,6 +10899,138 @@ bool VectorExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
   return Success(APValue(ResultElements.data(), ResultElements.size()), E);
 }
 
+static bool EvaluateVectorOrLValue(APValue &Result, EvalInfo &Info,
+                                   const Expr *E, const QualType &Type) {
+  if (!Evaluate(Result, Info, E))
+    return false;
+
+  if (Result.isLValue()) {
+    // Source of the data is an lvalue; Manually handle the lvalue as if
+    // it was an rvalue to get the current APValue.
+    LValue LValueFound;
+    LValueFound.setFrom(Info.Ctx, Result);
+    if (!handleLValueToRValueConversion(Info, E, Type, LValueFound, Result)) {
+      return false;
+    }
+  }
+
+  if (!Result.isVector()) {
+    return false;
+  }
+  return true;
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RKSimon wrote:

Just use `return Result.isVector()` ?

https://github.com/llvm/llvm-project/pull/76615