[clang] [Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow AVX/AVX512 subvector insertion intrinsics to be used in constexpr #157709 (PR #158778)

[Timm Baeder via cfe-commits]

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@@ -2937,6 +2937,56 @@ static bool interp__builtin_elementwise_triop(
   return true;
 }
 
+static bool interp__builtin_x86_insert_subvector(InterpState &S, CodePtr OpPC,
+                                                 const CallExpr *Call,
+                                                 unsigned ID) {
+  assert(Call->getNumArgs() == 3);
+
+  PrimType ImmPT = *S.getContext().classify(Call->getArg(2));
+  APSInt ImmAPS = popToAPSInt(S.Stk, ImmPT);
+  uint64_t Index = ImmAPS.getZExtValue();
+
+  const Pointer &SubVec = S.Stk.pop<Pointer>();
+  if (!SubVec.getFieldDesc()->isPrimitiveArray()) {
+    return Invalid(S, OpPC);
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tbaederr wrote:

Just return false? The diagnostic output with `Invalid()` talks about an invalid expression otherwise and I don't believe this matches the output of the current interpreter.
Also remove the braces for single-statement if statements.

https://github.com/llvm/llvm-project/pull/158778