From 068e0e001d63a76fcec0cb585ffe8832794115eb Mon Sep 17 00:00:00 2001
From: =?utf8?q?Timm=20B=C3=A4der?= <tbaeder@redhat.com>
Date: Fri, 13 Jan 2023 22:22:36 +0100
Subject: [PATCH] [clang][Interp][NFC] Add failing test case for
 InterpFrame::describe()

---
 clang/test/AST/Interp/constexpr-nqueens.cpp | 66 +++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 clang/test/AST/Interp/constexpr-nqueens.cpp

diff --git a/clang/test/AST/Interp/constexpr-nqueens.cpp b/clang/test/AST/Interp/constexpr-nqueens.cpp
new file mode 100644
index 0000000..ffe8553
--- /dev/null
+++ b/clang/test/AST/Interp/constexpr-nqueens.cpp
@@ -0,0 +1,66 @@
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=ref %s
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -fexperimental-new-constant-interpreter -verify %s
+
+/// This is a version of the nqueens.cpp from SemaCXX/,
+/// but we don't initialize the State variable in the
+/// Board constructors.
+/// This tests that InterpFrame::describe().
+
+// FIXME: With the new interpreter, most of the described frames are
+//  currently broken in one way or another.
+
+typedef unsigned long uint64_t;
+
+struct Board {
+  uint64_t State;
+  bool Failed;
+
+  constexpr Board() : Failed(false) {}
+  constexpr Board(const Board &O) : Failed(O.Failed) {}
+  constexpr Board(uint64_t State, bool Failed = false) :
+    Failed(Failed) {}
+  constexpr Board addQueen(int Row, int Col) const {
+    return Board(State | ((uint64_t)Row << (Col * 4))); // ref-note {{read of uninitialized object}}
+  }
+  constexpr int getQueenRow(int Col) const {
+    return (State >> (Col * 4)) & 0xf;
+  }
+  constexpr bool ok(int Row, int Col) const {
+    return okRecurse(Row, Col, 0);
+  }
+  constexpr bool okRecurse(int Row, int Col, int CheckCol) const {
+    return Col == CheckCol ? true :
+           getQueenRow(CheckCol) == Row ? false :
+           getQueenRow(CheckCol) == Row + (Col - CheckCol) ? false :
+           getQueenRow(CheckCol) == Row + (CheckCol - Col) ? false :
+           okRecurse(Row, Col, CheckCol + 1);
+  }
+  constexpr bool at(int Row, int Col) const {
+    return getQueenRow(Col) == Row;
+  }
+  constexpr bool check(const char *, int=0, int=0) const;
+};
+
+constexpr Board buildBoardRecurse(int N, int Col, const Board &B);
+constexpr Board buildBoardScan(int N, int Col, int Row, const Board &B);
+constexpr Board tryBoard(const Board &Try,
+                         int N, int Col, int Row, const Board &B) {
+  return Try.Failed ? buildBoardScan(N, Col, Row, B) : Try;
+}
+constexpr Board buildBoardScan(int N, int Col, int Row, const Board &B) {
+  return Row == N ? Board(0, true) :
+         B.ok(Row, Col) ?
+         tryBoard(buildBoardRecurse(N, Col + 1, B.addQueen(Row, Col)), // ref-note {{in call to '&Board()->addQueen(0, 0)}}
+                  N, Col, Row+1, B) :
+         buildBoardScan(N, Col, Row + 1, B);
+}
+constexpr Board buildBoardRecurse(int N, int Col, const Board &B) {
+  return Col == N ? B : buildBoardScan(N, Col, 0, B); // ref-note {{in call to 'buildBoardScan(8, 0, 0, Board())'}}
+}
+constexpr Board buildBoard(int N) {
+  return buildBoardRecurse(N, 0, Board()); // ref-note {{in call to 'buildBoardRecurse(8, 0, Board())'}}
+}
+
+constexpr Board q8 = buildBoard(8); // ref-error {{must be initialized by a constant expression}} \
+                                    // ref-note {{in call to 'buildBoard(8)'}} \
+                                    // expected-error {{must be initialized by a constant expression}}
-- 
2.7.4