[clang][Interp] Implement add and sub compound assign operators

[aaron.ballman]

clang/test/AST/Interp/literals.cpp

412

I'd also like some test cases where the result of the operation is discarded. e.g.,

constexpr int func() {
  int i = 12;
  i += 10;
  return i;
}
static_assert(func() == 22);

and a test with a float-point type (okay for it to fail for the moment):

constexpr float func() {
  float f = 1.0f;
  f += 10.0f;
  return f;
}
static_assert(func() == 11.0f);

426

We also need tests for failure situations:

constexpr int func() {
  int i = __INT_MAX__;
  i += 1; // oops
  return i;
}

constexpr int another() {
  int i = __INT_MIN__;
  i -= 1; // oops
  return i;
}

[tbaeder]

clang/test/AST/Interp/literals.cpp

426

woops, I was sure I added this but it was for the ++/-- patch it seems.

[aaron.ballman]

LGTM!

clang/lib/AST/Interp/ByteCodeExprGen.h

public:
   bool VisitMemberExpr(const MemberExpr *E);
   bool VisitArrayInitIndexExpr(const ArrayInitIndexExpr *E);
   bool VisitOpaqueValueExpr(const OpaqueValueExpr *E);
   bool VisitAbstractConditionalOperator(const AbstractConditionalOperator *E);
   bool VisitStringLiteral(const StringLiteral *E);
   bool VisitCharacterLiteral(const CharacterLiteral *E);
   bool VisitExprWithCleanups(const ExprWithCleanups *E);
   bool VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *E);
+  bool VisitCompoundAssignOperator(const CompoundAssignOperator *E);
 
 protected:
   bool visitExpr(const Expr *E) override;
   bool visitDecl(const VarDecl *VD) override;
 
 protected:
   /// Emits scope cleanup instructions.
   void emitCleanup();

clang/lib/AST/Interp/ByteCodeExprGen.cpp

if (Optional<unsigned> LocalIndex =
         return false;
       return this->emitGetPtrLocal(*LocalIndex, E);
     }
   }
 
   return false;
 }
 
+template <class Emitter>
+bool ByteCodeExprGen<Emitter>::VisitCompoundAssignOperator(
+    const CompoundAssignOperator *E) {
+  const Expr *LHS = E->getLHS();
+  const Expr *RHS = E->getRHS();
+  Optional<PrimType> LT = classify(E->getLHS()->getType());
+  Optional<PrimType> RT = classify(E->getRHS()->getType());
+
+  if (!LT || !RT)
+    return false;
+
+  assert(!E->getType()->isPointerType() &&
+         "Support pointer arithmethic in compound assignment operators");
+
+  // Get LHS pointer, load its value and get RHS value.
+  if (!visit(LHS))
+    return false;
+  if (!this->emitLoad(*LT, E))
+    return false;
+  if (!visit(RHS))
+    return false;
+
+  // Perform operation.
+  switch (E->getOpcode()) {
+  case BO_AddAssign:
+    if (!this->emitAdd(*LT, E))
+      return false;
+    break;
+  case BO_SubAssign:
+    if (!this->emitSub(*LT, E))
+      return false;
+    break;
+
+  case BO_MulAssign:
+  case BO_DivAssign:
+  case BO_RemAssign:
+  case BO_ShlAssign:
+  case BO_ShrAssign:
+  case BO_AndAssign:
+  case BO_XorAssign:
+  case BO_OrAssign:
+  default:
+    llvm_unreachable("Unimplemented compound assign operator");
+  }
+
+  // And store the result in LHS.
+  if (DiscardResult)
+    return this->emitStorePop(*LT, E);
+  return this->emitStore(*LT, E);
+}
+
 template <class Emitter> bool ByteCodeExprGen<Emitter>::discard(const Expr *E) {
   OptionScope<Emitter> Scope(this, /*NewDiscardResult=*/true);
   return this->Visit(E);
 }
 
 template <class Emitter>
 bool ByteCodeExprGen<Emitter>::visit(const Expr *E) {
   OptionScope<Emitter> Scope(this, /*NewDiscardResult=*/false);

clang/test/AST/Interp/literals.cpp

constexpr int OverUnderFlow() { // ref-error {{never produces a constant expression}}
     ++a; // ref-note {{is outside the range}}
     // FIXME: Overflow
 
     int b = INT_MIN;
     --b; // FIXME: Underflow
 
     return -1;
   }
+
+  constexpr int getTwo() {
+    int i = 1;
+    return (i += 1);
+  }
+  static_assert(getTwo() == 2, "");
+
+  constexpr int sub(int a) {
+    return (a -= 2);
+  }
+  static_assert(sub(7) == 5, "");
+
+  constexpr int subAll(int a) {
+    return (a -= a);
+  }
+  static_assert(subAll(213) == 0);
+
 };
 #endif