c++: Use fold_non_dependent_expr rather than maybe_constant_value in __builtin_shufflevector handling [PR106001]

In this case the STATIC_CAST_EXPR expressions in the call aren't
type nor value dependent, but maybe_constant_value still ICEs on those
when processing_template_decl.  Calling fold_non_dependent_expr on it
instead fixes the ICE and folds them to INTEGER_CSTs.

2022-06-17  Jakub Jelinek  <[email protected]>

	PR c++/106001
	* typeck.cc (build_x_shufflevector): Use fold_non_dependent_expr
	instead of maybe_constant_value.

	* g++.dg/ext/builtin-shufflevector-4.C: New test.

Author: jakubjelinek

gcc/cp/typeck.cc

@@ -6344,7 +6344,7 @@ build_x_shufflevector (location_t loc, vec<tree, va_gc> *args,
   auto_vec<tree, 16> mask;
   for (unsigned i = 2; i < args->length (); ++i)
     {
-      tree idx = maybe_constant_value ((*args)[i]);
+      tree idx = fold_non_dependent_expr ((*args)[i], complain);
       mask.safe_push (idx);
     }
   tree exp = c_build_shufflevector (loc, arg0, arg1, mask, complain & tf_error);

gcc/testsuite/g++.dg/ext/builtin-shufflevector-4.C

@@ -0,0 +1,18 @@
+// PR c++/106001
+// { dg-do compile }
+
+typedef int V __attribute__((vector_size (2 * sizeof (int))));
+
+template <int>
+void
+foo ()
+{
+  V v = {};
+  v = __builtin_shufflevector (v, v, static_cast<char>(1), static_cast<char>(0));
+}
+
+void
+bar ()
+{
+  foo <0> ();
+}