[clang][Interp] Add basic support for AddrLabelExprs

Just create a local variable for them.

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -2488,6 +2488,16 @@ bool ByteCodeExprGen<Emitter>::VisitRecoveryExpr(const RecoveryExpr *E) {
   return this->emitError(E);
 }
 
+template <class Emitter>
+bool ByteCodeExprGen<Emitter>::VisitAddrLabelExpr(const AddrLabelExpr *E) {
+  assert(E->getType()->isVoidPointerType());
+
+  unsigned Offset = allocateLocalPrimitive(
+      E->getLabel(), PT_Ptr, /*IsConst=*/true, /*IsExtended=*/false);
+
+  return this->emitGetLocal(PT_Ptr, Offset, E);
+}
+
 template <class Emitter> bool ByteCodeExprGen<Emitter>::discard(const Expr *E) {
   OptionScope<Emitter> Scope(this, /*NewDiscardResult=*/true,
                              /*NewInitializing=*/false);

clang/lib/AST/Interp/ByteCodeExprGen.h

@@ -122,6 +122,7 @@ class ByteCodeExprGen : public ConstStmtVisitor<ByteCodeExprGen<Emitter>, bool>,
   bool VisitPseudoObjectExpr(const PseudoObjectExpr *E);
   bool VisitPackIndexingExpr(const PackIndexingExpr *E);
   bool VisitRecoveryExpr(const RecoveryExpr *E);
+  bool VisitAddrLabelExpr(const AddrLabelExpr *E);
 
 protected:
   bool visitExpr(const Expr *E) override;

clang/test/AST/Interp/c.c

@@ -273,3 +273,8 @@ int test3(void) {
 /// This tests that we have full type info, even for values we cannot read.
 int dummyarray[5];
 _Static_assert(&dummyarray[0] < &dummyarray[1], ""); // pedantic-warning {{GNU extension}}
+
+void addrlabelexpr(void) {
+ a0: ;
+  static void *ps[] = { &&a0 }; // pedantic-warning {{use of GNU address-of-label extension}}
+}