[clang][bytecode] Explicit composite array descriptor types (#129376)

When creating descriptor for array element types, we only save the
original source, e.g. int[2][2][2]. So later calls to getType() of the
element descriptors will also return int[2][2][2], instead of e.g.
int[2][2] for the second dimension.
Fix this by explicitly tracking the array types.
The last attached test case used to have an lvalue offset of 32 instead
of 24.

We should do this for more desriptor types though and not just composite
array, but I'm leaving that to a later patch.

Author: tbaederr

clang/lib/AST/ByteCode/Descriptor.cpp

@@ -367,10 +367,12 @@ Descriptor::Descriptor(const DeclTy &D, PrimType Type, MetadataSize MD,
 }
 
 /// Arrays of composite elements.
-Descriptor::Descriptor(const DeclTy &D, const Descriptor *Elem, MetadataSize MD,
+Descriptor::Descriptor(const DeclTy &D, const Type *SourceTy,
+                       const Descriptor *Elem, MetadataSize MD,
                        unsigned NumElems, bool IsConst, bool IsTemporary,
                        bool IsMutable)
-    : Source(D), ElemSize(Elem->getAllocSize() + sizeof(InlineDescriptor)),
+    : Source(D), SourceType(SourceTy),
+      ElemSize(Elem->getAllocSize() + sizeof(InlineDescriptor)),
       Size(ElemSize * NumElems), MDSize(MD.value_or(0)),
       AllocSize(std::max<size_t>(alignof(void *), Size) + MDSize),
       ElemDesc(Elem), IsConst(IsConst), IsMutable(IsMutable),
@@ -410,6 +412,8 @@ Descriptor::Descriptor(const DeclTy &D)
 }
 
 QualType Descriptor::getType() const {
+  if (SourceType)
+    return QualType(SourceType, 0);
   if (const auto *D = asValueDecl())
     return D->getType();
   if (const auto *T = dyn_cast_if_present<TypeDecl>(asDecl()))

clang/lib/AST/ByteCode/Descriptor.h

@@ -124,6 +124,7 @@ struct Descriptor final {
 private:
   /// Original declaration, used to emit the error message.
   const DeclTy Source;
+  const Type *SourceType = nullptr;
   /// Size of an element, in host bytes.
   const unsigned ElemSize;
   /// Size of the storage, in host bytes.
@@ -186,8 +187,9 @@ struct Descriptor final {
              bool IsTemporary, UnknownSize);
 
   /// Allocates a descriptor for an array of composites.
-  Descriptor(const DeclTy &D, const Descriptor *Elem, MetadataSize MD,
-             unsigned NumElems, bool IsConst, bool IsTemporary, bool IsMutable);
+  Descriptor(const DeclTy &D, const Type *SourceTy, const Descriptor *Elem,
+             MetadataSize MD, unsigned NumElems, bool IsConst, bool IsTemporary,
+             bool IsMutable);
 
   /// Allocates a descriptor for an array of composites of unknown size.
   Descriptor(const DeclTy &D, const Descriptor *Elem, MetadataSize MD,

clang/lib/AST/ByteCode/DynamicAllocator.cpp

@@ -57,8 +57,10 @@ Block *DynamicAllocator::allocate(const Descriptor *ElementDesc,
   assert(ElementDesc->getMetadataSize() == 0);
   // Create a new descriptor for an array of the specified size and
   // element type.
+  // FIXME: Pass proper element type.
   const Descriptor *D = allocateDescriptor(
-      ElementDesc->asExpr(), ElementDesc, Descriptor::InlineDescMD, NumElements,
+      ElementDesc->asExpr(), nullptr, ElementDesc, Descriptor::InlineDescMD,
+      NumElements,
       /*IsConst=*/false, /*IsTemporary=*/false, /*IsMutable=*/false);
   return allocate(D, EvalID, AllocForm);
 }

clang/lib/AST/ByteCode/Program.cpp

@@ -419,7 +419,7 @@ Descriptor *Program::createDescriptor(const DeclTy &D, const Type *Ty,
         unsigned ElemSize = ElemDesc->getAllocSize() + sizeof(InlineDescriptor);
         if (std::numeric_limits<unsigned>::max() / ElemSize <= NumElems)
           return {};
-        return allocateDescriptor(D, ElemDesc, MDSize, NumElems, IsConst,
+        return allocateDescriptor(D, Ty, ElemDesc, MDSize, NumElems, IsConst,
                                   IsTemporary, IsMutable);
       }
     }

clang/unittests/AST/ByteCode/toAPValue.cpp

@@ -254,3 +254,69 @@ TEST(ToAPValue, MemberPointers) {
     ASSERT_EQ(A.getKind(), APValue::MemberPointer);
   }
 }
+
+/// Compare outputs between the two interpreters.
+TEST(ToAPValue, Comparison) {
+  constexpr char Code[] =
+      "constexpr int GI = 12;\n"
+      "constexpr const int *PI = &GI;\n"
+      "struct S{int a; };\n"
+      "constexpr S GS[] = {{}, {}};\n"
+      "constexpr const S* OS = GS + 1;\n"
+      "constexpr S DS = *OS;\n"
+      "constexpr int IA[2][2][2] = {{{1, 2}, {3, 4}}, {{5, 6}, {7, 8}}};\n"
+      "constexpr const int *PIA = IA[1][1];\n";
+
+  for (const char *Arg : {"", "-fexperimental-new-constant-interpreter"}) {
+    auto AST = tooling::buildASTFromCodeWithArgs(Code, {Arg});
+
+    auto getDecl = [&](const char *Name) -> const VarDecl * {
+      auto Nodes =
+          match(valueDecl(hasName(Name)).bind("var"), AST->getASTContext());
+      assert(Nodes.size() == 1);
+      const auto *D = Nodes[0].getNodeAs<ValueDecl>("var");
+      assert(D);
+      return cast<VarDecl>(D);
+    };
+
+    {
+      const VarDecl *GIDecl = getDecl("GI");
+      const APValue *V = GIDecl->evaluateValue();
+      ASSERT_TRUE(V->isInt());
+    }
+
+    {
+      const VarDecl *GIDecl = getDecl("GI");
+      const VarDecl *PIDecl = getDecl("PI");
+      const APValue *V = PIDecl->evaluateValue();
+      ASSERT_TRUE(V->isLValue());
+      ASSERT_TRUE(V->hasLValuePath());
+      ASSERT_EQ(V->getLValueBase().get<const ValueDecl *>(), GIDecl);
+      ASSERT_EQ(V->getLValuePath().size(), 0u);
+    }
+
+    {
+      const APValue *V = getDecl("OS")->evaluateValue();
+      ASSERT_TRUE(V->isLValue());
+      ASSERT_EQ(V->getLValueOffset().getQuantity(), (unsigned)sizeof(int));
+      ASSERT_TRUE(V->hasLValuePath());
+      ASSERT_EQ(V->getLValuePath().size(), 1u);
+      ASSERT_EQ(V->getLValuePath()[0].getAsArrayIndex(), 1u);
+    }
+
+    {
+      const APValue *V = getDecl("DS")->evaluateValue();
+      ASSERT_TRUE(V->isStruct());
+    }
+    {
+      const APValue *V = getDecl("PIA")->evaluateValue();
+      ASSERT_TRUE(V->isLValue());
+      ASSERT_TRUE(V->hasLValuePath());
+      ASSERT_EQ(V->getLValuePath().size(), 3u);
+      ASSERT_EQ(V->getLValuePath()[0].getAsArrayIndex(), 1u);
+      ASSERT_EQ(V->getLValuePath()[1].getAsArrayIndex(), 1u);
+      ASSERT_EQ(V->getLValuePath()[2].getAsArrayIndex(), 0u);
+      ASSERT_EQ(V->getLValueOffset().getQuantity(), (unsigned)sizeof(int) * 6);
+    }
+  }
+}