[clang] [X86][Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow element extraction/insertion intrinsics to be used in constexpr #159753 (PR #161302)

[Simon Pilgrim via cfe-commits]

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@@ -2878,6 +2878,60 @@ static bool interp__builtin_x86_insert_subvector(InterpState &S, CodePtr OpPC,
   return true;
 }
 
+static bool interp__builtin_vec_ext(InterpState &S, CodePtr OpPC,
+                                    const CallExpr *Call, unsigned ID) {
+  assert(Call->getNumArgs() == 2);
+
+  APSInt ImmAPS = popToAPSInt(S, Call->getArg(1));
+  const Pointer &Vec = S.Stk.pop<Pointer>();
+  if (!Vec.getFieldDesc()->isPrimitiveArray())
+    return false;
+
+  unsigned NumElts = Vec.getNumElems();
+  unsigned Index = static_cast<unsigned>(ImmAPS.getZExtValue() & (NumElts - 1));
+
+  switch (ID) {
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RKSimon wrote:

We don't actually care whether this is integer/float  - any reason we can't use TYPE_SWITCH ? We're going to have the same issue with shuffles

https://github.com/llvm/llvm-project/pull/161302