[clang][bytecode] Handle __builtin_wcslen (llvm#118446)

... just like strlen.

Author: tbaederr

clang/lib/AST/ByteCode/InterpBuiltin.cpp

@@ -243,7 +243,7 @@ static bool interp__builtin_strlen(InterpState &S, CodePtr OpPC,
   unsigned ID = Func->getBuiltinID();
   const Pointer &StrPtr = getParam<Pointer>(Frame, 0);
 
-  if (ID == Builtin::BIstrlen)
+  if (ID == Builtin::BIstrlen || ID == Builtin::BIwcslen)
     diagnoseNonConstexprBuiltin(S, OpPC, ID);
 
   if (!CheckArray(S, OpPC, StrPtr))
@@ -1857,6 +1857,8 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
     break;
   case Builtin::BI__builtin_strlen:
   case Builtin::BIstrlen:
+  case Builtin::BI__builtin_wcslen:
+  case Builtin::BIwcslen:
     if (!interp__builtin_strlen(S, OpPC, Frame, F, Call))
       return false;
     break;

clang/test/AST/ByteCode/builtin-functions.cpp

@@ -7,6 +7,10 @@
 // RUN: %clang_cc1 -triple avr -std=c++20 -Wno-string-plus-int -fexperimental-new-constant-interpreter %s -verify=expected,both
 // RUN: %clang_cc1 -triple avr -std=c++20 -Wno-string-plus-int -verify=ref,both %s -Wno-constant-evaluated
 
+extern "C" {
+  typedef decltype(sizeof(int)) size_t;
+  extern size_t wcslen(const wchar_t *p);
+}
 
 namespace strcmp {
   constexpr char kFoobar[6] = {'f','o','o','b','a','r'};
@@ -85,6 +89,14 @@ constexpr const char *a = "foo\0quux";
   constexpr char d[] = { 'f', 'o', 'o' }; // no nul terminator.
   constexpr int bad = __builtin_strlen(d); // both-error {{constant expression}} \
                                            // both-note {{one-past-the-end}}
+
+  constexpr int wn = __builtin_wcslen(L"hello");
+  static_assert(wn == 5);
+  constexpr int wm = wcslen(L"hello"); // both-error {{constant expression}} \
+                                       // both-note {{non-constexpr function 'wcslen' cannot be used in a constant expression}}
+
+  int arr[3]; // both-note {{here}}
+  int wk = arr[wcslen(L"hello")]; // both-warning {{array index 5}}
 }
 
 namespace nan {