[clang][Interp] Allow inc/dec on boolean values

The warnings or errors are emitted in Sema, but we still need to
do the operation and provide a reasonable result.

Author: tbaederr

clang/lib/AST/Interp/Interp.h

@@ -199,6 +199,8 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
 bool InterpretOffsetOf(InterpState &S, CodePtr OpPC, const OffsetOfExpr *E,
                        llvm::ArrayRef<int64_t> ArrayIndices, int64_t &Result);
 
+inline bool Invalid(InterpState &S, CodePtr OpPC);
+
 enum class ArithOp { Add, Sub };
 
 //===----------------------------------------------------------------------===//
@@ -522,6 +524,11 @@ bool IncDecHelper(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
   if (Ptr.isDummy())
     return false;
 
+  if constexpr (std::is_same_v<T, Boolean>) {
+    if (!S.getLangOpts().CPlusPlus14)
+      return Invalid(S, OpPC);
+  }
+
   const T &Value = Ptr.deref<T>();
   T Result;
 

clang/lib/AST/Interp/Opcodes.td

@@ -563,10 +563,10 @@ def Inv: Opcode {
 }
 
 // Increment and decrement.
-def Inc: IntegerOpcode;
-def IncPop : IntegerOpcode;
-def Dec: IntegerOpcode;
-def DecPop: IntegerOpcode;
+def Inc: AluOpcode;
+def IncPop : AluOpcode;
+def Dec: AluOpcode;
+def DecPop: AluOpcode;
 
 // Float increment and decrement.
 def Incf: FloatOpcode;

clang/test/AST/Interp/literals.cpp

@@ -1131,3 +1131,40 @@ namespace nullptrsub {
     f = (char *)((char *)0 - (char *)0);
   }
 }
+
+namespace incdecbool {
+#if __cplusplus >= 201402L
+  constexpr bool incb(bool c) {
+    if (!c)
+      ++c;
+    else {++c; c++; }
+#if __cplusplus >= 202002L
+    // both-error@-3 {{ISO C++17 does not allow incrementing expression of type bool}}
+    // both-error@-3 2{{ISO C++17 does not allow incrementing expression of type bool}}
+#else
+    // both-warning@-6 {{incrementing expression of type bool is deprecated and incompatible with C++17}}
+#endif
+    return c;
+  }
+  static_assert(incb(false), "");
+  static_assert(incb(true), "");
+  static_assert(incb(true) == 1, "");
+#endif
+
+
+#if __cplusplus == 201103L
+  constexpr bool foo() { // both-error {{never produces a constant expression}}
+    bool b = true; // both-warning {{variable declaration in a constexpr function is a C++14 extension}}
+    b++; // both-warning {{incrementing expression of type bool is deprecated and incompatible with C++17}} \
+         // both-warning {{use of this statement in a constexpr function is a C++14 extension}} \
+         // both-note 2{{subexpression not valid in a constant expression}}
+
+    return b;
+  }
+  static_assert(foo() == 1, ""); // both-error {{not an integral constant expression}} \
+                                 // both-note {{in call to}}
+#endif
+
+
+
+}

clang/test/SemaCXX/bool.cpp

@@ -2,6 +2,11 @@
 // RUN: %clang_cc1 %std_cxx98-14 -fsyntax-only -verify=expected,precxx17 -Wno-constant-conversion -Wno-deprecated -Wdeprecated-increment-bool %s
 // RUN: %clang_cc1 %std_cxx17- -fsyntax-only -verify=expected,cxx17 -Wno-constant-conversion -Wno-deprecated -Wdeprecated-increment-bool %s
 
+// RUN: %clang_cc1 %std_cxx98-14 -fsyntax-only -verify=expected,precxx17 -Wno-constant-conversion %s -fexperimental-new-constant-interpreter
+// RUN: %clang_cc1 %std_cxx98-14 -fsyntax-only -verify=expected,precxx17 -Wno-constant-conversion -Wno-deprecated -Wdeprecated-increment-bool %s -fexperimental-new-constant-interpreter
+// RUN: %clang_cc1 %std_cxx17- -fsyntax-only -verify=expected,cxx17 -Wno-constant-conversion -Wno-deprecated -Wdeprecated-increment-bool %s -fexperimental-new-constant-interpreter
+
+
 // Bool literals can be enum values.
 enum {
   ReadWrite = false,