[clang] Implement dump() for AddrLabelDiff APValues (#169505)

Author: tbaederr

clang/lib/AST/TextNodeDumper.cpp

@@ -850,7 +850,10 @@ void TextNodeDumper::Visit(const APValue &Value, QualType Ty) {
     return;
   }
   case APValue::AddrLabelDiff:
-    OS << "AddrLabelDiff <todo>";
+    OS << "AddrLabelDiff ";
+    OS << "&&" << Value.getAddrLabelDiffLHS()->getLabel()->getName();
+    OS << " - ";
+    OS << "&&" << Value.getAddrLabelDiffRHS()->getLabel()->getName();
     return;
   }
   llvm_unreachable("Unknown APValue kind!");

clang/test/AST/ast-dump-APValue-addrlabeldiff.c

@@ -0,0 +1,22 @@
+// Test without serialization:
+// RUN: %clang_cc1 -std=c23 -ast-dump %s -ast-dump-filter Test \
+// RUN: | FileCheck --strict-whitespace --match-full-lines %s
+//
+// Test with serialization:
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -Wno-unused-value -std=c23 -emit-pch -o %t %s
+// RUN: %clang_cc1 -x c -triple x86_64-unknown-unknown -Wno-unused-value -std=c23 \
+// RUN:           -include-pch %t -ast-dump-all -ast-dump-filter Test /dev/null \
+// RUN: | sed -e "s/ <undeserialized declarations>//" -e "s/ imported//" \
+// RUN: | FileCheck --strict-whitespace --match-full-lines %s
+
+
+// CHECK:  |   |-value: AddrLabelDiff &&l2 - &&l1
+int Test(void) {
+  constexpr char ar = &&l2 - &&l1;
+l1:
+  return 10;
+l2:
+  return 11;
+}
+
+