[clang][Interp] Fix non-primitive ltor casts

This doesn't happen in C++ since it will instead call the
struct's copy constructor. However, in C, this needs to work.

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -82,15 +82,27 @@ bool ByteCodeExprGen<Emitter>::VisitCastExpr(const CastExpr *CE) {
     if (DiscardResult)
       return this->discard(SubExpr);
 
-    if (SubExpr->getType()->isAnyComplexType())
-      return this->delegate(SubExpr);
+    std::optional<PrimType> SubExprT = classify(SubExpr->getType());
+    // Prepare storage for the result.
+    if (!Initializing && !SubExprT) {
+      std::optional<unsigned> LocalIndex =
+          allocateLocal(SubExpr, /*IsExtended=*/false);
+      if (!LocalIndex)
+        return false;
+      if (!this->emitGetPtrLocal(*LocalIndex, CE))
+        return false;
+    }
 
     if (!this->visit(SubExpr))
       return false;
 
-    if (std::optional<PrimType> SubExprT = classify(SubExpr->getType()))
+    if (SubExprT)
       return this->emitLoadPop(*SubExprT, CE);
-    return false;
+
+    // If the subexpr type is not primitive, we need to perform a copy here.
+    // This happens for example in C when dereferencing a pointer of struct
+    // type.
+    return this->emitMemcpy(CE);
   }
 
   case CK_UncheckedDerivedToBase:
@@ -3247,53 +3259,20 @@ bool ByteCodeExprGen<Emitter>::VisitDeclRefExpr(const DeclRefExpr *E) {
   // pointer to the actual value) instead of a pointer to the pointer to the
   // value.
   bool IsReference = D->getType()->isReferenceType();
-  // Complex values are copied in the AST via a simply assignment or
-  // ltor cast. But we represent them as two-element arrays, which means
-  // we pass them around as pointers. So, to assignm from them, we will
-  // have to copy both (primitive) elements instead.
-  bool IsComplex = D->getType()->isAnyComplexType();
 
   // Check for local/global variables and parameters.
   if (auto It = Locals.find(D); It != Locals.end()) {
     const unsigned Offset = It->second.Offset;
-    // FIXME: Fix the code duplication here with the code in the global case.
-    if (Initializing && IsComplex) {
-      PrimType ElemT = classifyComplexElementType(D->getType());
-      for (unsigned I = 0; I != 2; ++I) {
-        if (!this->emitGetPtrLocal(Offset, E))
-          return false;
-        if (!this->emitArrayElemPop(ElemT, I, E))
-          return false;
-        if (!this->emitInitElem(ElemT, I, E))
-          return false;
-      }
-      return true;
-    }
-
     if (IsReference)
       return this->emitGetLocal(PT_Ptr, Offset, E);
     return this->emitGetPtrLocal(Offset, E);
   } else if (auto GlobalIndex = P.getGlobal(D)) {
-    if (Initializing && IsComplex) {
-      PrimType ElemT = classifyComplexElementType(D->getType());
-      for (unsigned I = 0; I != 2; ++I) {
-        if (!this->emitGetPtrGlobal(*GlobalIndex, E))
-          return false;
-        if (!this->emitArrayElemPop(ElemT, I, E))
-          return false;
-        if (!this->emitInitElem(ElemT, I, E))
-          return false;
-      }
-      return true;
-    }
-
     if (IsReference)
       return this->emitGetGlobalPtr(*GlobalIndex, E);
 
     return this->emitGetPtrGlobal(*GlobalIndex, E);
   } else if (const auto *PVD = dyn_cast<ParmVarDecl>(D)) {
     if (auto It = this->Params.find(PVD); It != this->Params.end()) {
-      // FIXME: _Complex initializing case?
       if (IsReference || !It->second.IsPtr)
         return this->emitGetParamPtr(It->second.Offset, E);
 

clang/lib/AST/Interp/Descriptor.cpp

@@ -233,9 +233,10 @@ static BlockMoveFn getMoveArrayPrim(PrimType Type) {
 Descriptor::Descriptor(const DeclTy &D, PrimType Type, MetadataSize MD,
                        bool IsConst, bool IsTemporary, bool IsMutable)
     : Source(D), ElemSize(primSize(Type)), Size(ElemSize),
-      MDSize(MD.value_or(0)), AllocSize(align(Size + MDSize)), IsConst(IsConst),
-      IsMutable(IsMutable), IsTemporary(IsTemporary), CtorFn(getCtorPrim(Type)),
-      DtorFn(getDtorPrim(Type)), MoveFn(getMovePrim(Type)) {
+      MDSize(MD.value_or(0)), AllocSize(align(Size + MDSize)), PrimT(Type),
+      IsConst(IsConst), IsMutable(IsMutable), IsTemporary(IsTemporary),
+      CtorFn(getCtorPrim(Type)), DtorFn(getDtorPrim(Type)),
+      MoveFn(getMovePrim(Type)) {
   assert(AllocSize >= Size);
   assert(Source && "Missing source");
 }
@@ -246,7 +247,7 @@ Descriptor::Descriptor(const DeclTy &D, PrimType Type, MetadataSize MD,
                        bool IsMutable)
     : Source(D), ElemSize(primSize(Type)), Size(ElemSize * NumElems),
       MDSize(MD.value_or(0)),
-      AllocSize(align(MDSize) + align(Size) + sizeof(InitMapPtr)),
+      AllocSize(align(MDSize) + align(Size) + sizeof(InitMapPtr)), PrimT(Type),
       IsConst(IsConst), IsMutable(IsMutable), IsTemporary(IsTemporary),
       IsArray(true), CtorFn(getCtorArrayPrim(Type)),
       DtorFn(getDtorArrayPrim(Type)), MoveFn(getMoveArrayPrim(Type)) {

clang/lib/AST/Interp/Descriptor.h

@@ -112,6 +112,10 @@ struct Descriptor final {
   const Record *const ElemRecord = nullptr;
   /// Descriptor of the array element.
   const Descriptor *const ElemDesc = nullptr;
+  /// The primitive type this descriptor was created for,
+  /// or the primitive element type in case this is
+  /// a primitive array.
+  const std::optional<PrimType> PrimT = std::nullopt;
   /// Flag indicating if the block is mutable.
   const bool IsConst = false;
   /// Flag indicating if a field is mutable.
@@ -183,6 +187,11 @@ struct Descriptor final {
     return Size;
   }
 
+  PrimType getPrimType() const {
+    assert(isPrimitiveArray() || isPrimitive());
+    return *PrimT;
+  }
+
   /// Returns the allocated size, including metadata.
   unsigned getAllocSize() const { return AllocSize; }
   /// returns the size of an element when the structure is viewed as an array.

clang/lib/AST/Interp/Interp.h

@@ -122,6 +122,9 @@ bool CheckNonNullArgs(InterpState &S, CodePtr OpPC, const Function *F,
 bool SetThreeWayComparisonField(InterpState &S, CodePtr OpPC,
                                 const Pointer &Ptr, const APSInt &IntValue);
 
+/// Copy the contents of Src into Dest.
+bool DoMemcpy(InterpState &S, CodePtr OpPC, const Pointer &Src, Pointer &Dest);
+
 /// Checks if the shift operation is legal.
 template <typename LT, typename RT>
 bool CheckShift(InterpState &S, CodePtr OpPC, const LT &LHS, const RT &RHS,
@@ -1487,6 +1490,16 @@ bool InitElemPop(InterpState &S, CodePtr OpPC, uint32_t Idx) {
   return true;
 }
 
+inline bool Memcpy(InterpState &S, CodePtr OpPC) {
+  const Pointer &Src = S.Stk.pop<Pointer>();
+  Pointer &Dest = S.Stk.peek<Pointer>();
+
+  if (!CheckLoad(S, OpPC, Src))
+    return false;
+
+  return DoMemcpy(S, OpPC, Src, Dest);
+}
+
 //===----------------------------------------------------------------------===//
 // AddOffset, SubOffset
 //===----------------------------------------------------------------------===//

clang/lib/AST/Interp/InterpBuiltin.cpp

@@ -1326,5 +1326,50 @@ bool SetThreeWayComparisonField(InterpState &S, CodePtr OpPC,
   return true;
 }
 
+bool DoMemcpy(InterpState &S, CodePtr OpPC, const Pointer &Src, Pointer &Dest) {
+  assert(Src.isLive() && Dest.isLive());
+
+  const Descriptor *SrcDesc = Src.getFieldDesc();
+  const Descriptor *DestDesc = Dest.getFieldDesc();
+
+  assert(!DestDesc->isPrimitive() && !SrcDesc->isPrimitive());
+
+  if (DestDesc->isPrimitiveArray()) {
+    assert(SrcDesc->isPrimitiveArray());
+    assert(SrcDesc->getNumElems() == DestDesc->getNumElems());
+    PrimType ET = DestDesc->getPrimType();
+    for (unsigned I = 0, N = DestDesc->getNumElems(); I != N; ++I) {
+      Pointer DestElem = Dest.atIndex(I);
+      TYPE_SWITCH(ET, {
+        DestElem.deref<T>() = Src.atIndex(I).deref<T>();
+        DestElem.initialize();
+      });
+    }
+    return true;
+  }
+
+  if (DestDesc->isRecord()) {
+    assert(SrcDesc->isRecord());
+    assert(SrcDesc->ElemRecord == DestDesc->ElemRecord);
+    const Record *R = DestDesc->ElemRecord;
+    for (const Record::Field &F : R->fields()) {
+      Pointer DestField = Dest.atField(F.Offset);
+      if (std::optional<PrimType> FT = S.Ctx.classify(F.Decl->getType())) {
+        TYPE_SWITCH(*FT, {
+          DestField.deref<T>() = Src.atField(F.Offset).deref<T>();
+          DestField.initialize();
+        });
+      } else {
+        return Invalid(S, OpPC);
+      }
+    }
+    return true;
+  }
+
+  // FIXME: Composite types.
+
+  return Invalid(S, OpPC);
+}
+
 } // namespace interp
 } // namespace clang

clang/lib/AST/Interp/Opcodes.td

@@ -720,3 +720,5 @@ def CheckNonNullArg : Opcode {
   let Types = [PtrTypeClass];
   let HasGroup = 1;
 }
+
+def Memcpy : Opcode;

clang/test/AST/Interp/c.c

@@ -201,3 +201,11 @@ void localCompoundLiteral(void) {
        // pedantic-ref-warning {{use of an empty initializer}}
   };
 }
+
+/// struct copy
+struct StrA {int a; };
+const struct StrA sa = { 12 };
+const struct StrA * const sb = &sa;
+const struct StrA sc = *sb;
+_Static_assert(sc.a == 12, ""); // pedantic-ref-warning {{GNU extension}} \
+                                // pedantic-expected-warning {{GNU extension}}