[clang] [Clang] Enable constexpr handling for builtin elementwise fshl/fshr (PR #153572)

[Timm Baeder via cfe-commits]

================
@@ -2817,6 +2817,82 @@ static bool interp__builtin_select(InterpState &S, CodePtr OpPC,
   return true;
 }
 
+static bool interp__builtin_elementwise_fsh(InterpState &S, CodePtr OpPC,
+                                            const CallExpr *Call,
+                                            unsigned BuiltinID) {
+  assert(Call->getNumArgs() == 3);
+
+  const QualType &Arg1Type = Call->getArg(0)->getType();
+  const QualType &Arg2Type = Call->getArg(1)->getType();
+  const QualType &Arg3Type = Call->getArg(2)->getType();
+
+  // Non-vector integer types.
+  if (!Arg1Type->isVectorType()) {
+    assert(!Arg2Type->isVectorType());
+    assert(!Arg3Type->isVectorType());
+    const APSInt &Shift = popToAPSInt(
+        S.Stk, *S.getContext().classify(Call->getArg(2)->getType()));
----------------
tbaederr wrote:

```suggestion
        S.Stk, *S.getContext().classify(Arg2Type));
```
etc.

https://github.com/llvm/llvm-project/pull/153572