[clang][bytecode] Create dummy pointers for non-reference DeclRefExprs (#113202)

... with non-constant initializers.

Author: tbaederr

clang/lib/AST/ByteCode/Compiler.cpp

@@ -2371,9 +2371,9 @@ bool Compiler<Emitter>::VisitStringLiteral(const StringLiteral *E) {
 
 template <class Emitter>
 bool Compiler<Emitter>::VisitObjCStringLiteral(const ObjCStringLiteral *E) {
-  if (std::optional<unsigned> I = P.getOrCreateDummy(E))
-    return this->emitGetPtrGlobal(*I, E);
-  return false;
+  if (DiscardResult)
+    return true;
+  return this->emitDummyPtr(E, E);
 }
 
 template <class Emitter>
@@ -3445,11 +3445,8 @@ bool Compiler<Emitter>::VisitCXXUuidofExpr(const CXXUuidofExpr *E) {
   assert(RD);
   // If the definiton of the result type is incomplete, just return a dummy.
   // If (and when) that is read from, we will fail, but not now.
-  if (!RD->isCompleteDefinition()) {
-    if (std::optional<unsigned> I = P.getOrCreateDummy(GuidDecl))
-      return this->emitGetPtrGlobal(*I, E);
-    return false;
-  }
+  if (!RD->isCompleteDefinition())
+    return this->emitDummyPtr(GuidDecl, E);
 
   std::optional<unsigned> GlobalIndex = P.getOrCreateGlobal(GuidDecl);
   if (!GlobalIndex)
@@ -3687,11 +3684,11 @@ bool Compiler<Emitter>::VisitObjCBoxedExpr(const ObjCBoxedExpr *E) {
   if (!E->isExpressibleAsConstantInitializer())
     return this->discard(SubExpr) && this->emitInvalid(E);
 
-  assert(classifyPrim(E) == PT_Ptr);
-  if (std::optional<unsigned> I = P.getOrCreateDummy(E))
-    return this->emitGetPtrGlobal(*I, E);
+  if (DiscardResult)
+    return true;
 
-  return false;
+  assert(classifyPrim(E) == PT_Ptr);
+  return this->emitDummyPtr(E, E);
 }
 
 template <class Emitter>
@@ -4483,15 +4480,9 @@ bool Compiler<Emitter>::VisitBuiltinCallExpr(const CallExpr *E,
       BuiltinID == Builtin::BI__builtin___NSStringMakeConstantString ||
       BuiltinID == Builtin::BI__builtin_ptrauth_sign_constant ||
       BuiltinID == Builtin::BI__builtin_function_start) {
-    if (std::optional<unsigned> GlobalOffset = P.getOrCreateDummy(E)) {
-      if (!this->emitGetPtrGlobal(*GlobalOffset, E))
-        return false;
-
-      if (PrimType PT = classifyPrim(E); PT != PT_Ptr && isPtrType(PT))
-        return this->emitDecayPtr(PT_Ptr, PT, E);
+    if (DiscardResult)
       return true;
-    }
-    return false;
+    return this->emitDummyPtr(E, E);
   }
 
   QualType ReturnType = E->getType();
@@ -6097,6 +6088,10 @@ bool Compiler<Emitter>::visitDeclRef(const ValueDecl *D, const Expr *E) {
 
           if (VD->evaluateValue())
             return revisit(VD);
+
+          if (!D->getType()->isReferenceType())
+            return this->emitDummyPtr(D, E);
+
           return this->emitInvalidDeclRef(cast<DeclRefExpr>(E),
                                           /*InitializerFailed=*/true, E);
         }
@@ -6109,23 +6104,7 @@ bool Compiler<Emitter>::visitDeclRef(const ValueDecl *D, const Expr *E) {
     }
   }
 
-  if (std::optional<unsigned> I = P.getOrCreateDummy(D)) {
-    if (!this->emitGetPtrGlobal(*I, E))
-      return false;
-    if (E->getType()->isVoidType())
-      return true;
-    // Convert the dummy pointer to another pointer type if we have to.
-    if (PrimType PT = classifyPrim(E); PT != PT_Ptr) {
-      if (isPtrType(PT))
-        return this->emitDecayPtr(PT_Ptr, PT, E);
-      return false;
-    }
-    return true;
-  }
-
-  if (const auto *DRE = dyn_cast<DeclRefExpr>(E))
-    return this->emitInvalidDeclRef(DRE, /*InitializerFailed=*/false, E);
-  return false;
+  return this->emitDummyPtr(D, E);
 }
 
 template <class Emitter>
@@ -6428,6 +6407,29 @@ bool Compiler<Emitter>::emitDestruction(const Descriptor *Desc,
   return this->emitRecordDestruction(Desc->ElemRecord, Loc);
 }
 
+/// Create a dummy pointer for the given decl (or expr) and
+/// push a pointer to it on the stack.
+template <class Emitter>
+bool Compiler<Emitter>::emitDummyPtr(const DeclTy &D, const Expr *E) {
+  assert(!DiscardResult && "Should've been checked before");
+
+  unsigned DummyID = P.getOrCreateDummy(D);
+
+  if (!this->emitGetPtrGlobal(DummyID, E))
+    return false;
+  if (E->getType()->isVoidType())
+    return true;
+
+  // Convert the dummy pointer to another pointer type if we have to.
+  if (PrimType PT = classifyPrim(E); PT != PT_Ptr) {
+    if (isPtrType(PT))
+      return this->emitDecayPtr(PT_Ptr, PT, E);
+    return false;
+  }
+
+  return true;
+}
+
 namespace clang {
 namespace interp {
 

clang/lib/AST/ByteCode/Compiler.h

@@ -370,6 +370,7 @@ class Compiler : public ConstStmtVisitor<Compiler<Emitter>, bool>,
                              const BinaryOperator *E);
   bool emitRecordDestruction(const Record *R, SourceInfo Loc);
   bool emitDestruction(const Descriptor *Desc, SourceInfo Loc);
+  bool emitDummyPtr(const DeclTy &D, const Expr *E);
   unsigned collectBaseOffset(const QualType BaseType,
                              const QualType DerivedType);
   bool emitLambdaStaticInvokerBody(const CXXMethodDecl *MD);

clang/lib/AST/ByteCode/Program.cpp

@@ -147,7 +147,7 @@ std::optional<unsigned> Program::getOrCreateGlobal(const ValueDecl *VD,
   return std::nullopt;
 }
 
-std::optional<unsigned> Program::getOrCreateDummy(const DeclTy &D) {
+unsigned Program::getOrCreateDummy(const DeclTy &D) {
   assert(D);
   // Dedup blocks since they are immutable and pointers cannot be compared.
   if (auto It = DummyVariables.find(D.getOpaqueValue());

clang/lib/AST/ByteCode/Program.h

@@ -85,7 +85,7 @@ class Program final {
                                             const Expr *Init = nullptr);
 
   /// Returns or creates a dummy value for unknown declarations.
-  std::optional<unsigned> getOrCreateDummy(const DeclTy &D);
+  unsigned getOrCreateDummy(const DeclTy &D);
 
   /// Creates a global and returns its index.
   std::optional<unsigned> createGlobal(const ValueDecl *VD, const Expr *Init);

clang/test/AST/ByteCode/records.cpp

@@ -1661,3 +1661,18 @@ namespace NullptrUpcast {
   constexpr A &ra = *nb; // both-error {{constant expression}} \
                          // both-note {{cannot access base class of null pointer}}
 }
+
+namespace NonConst {
+  template <int I>
+  struct S {
+    static constexpr int Size = I;
+    constexpr int getSize() const { return I; }
+    explicit S(int a) {}
+  };
+
+  void func() {
+    int a,b ;
+    const S<10> s{a};
+    static_assert(s.getSize() == 10, "");
+  }
+}