[clang] [clang][bytecode] Improve __builtin_{,dynamic_}object_size implementation (PR #153601)

[Timm Baeder via cfe-commits]

================
@@ -2170,29 +2170,32 @@ static bool interp__builtin_memchr(InterpState &S, CodePtr OpPC,
   return true;
 }
 
-static unsigned computeFullDescSize(const ASTContext &ASTCtx,
-                                    const Descriptor *Desc) {
-
+static std::optional<unsigned> computeFullDescSize(const ASTContext &ASTCtx,
+                                                   const Descriptor *Desc) {
   if (Desc->isPrimitive())
     return ASTCtx.getTypeSizeInChars(Desc->getType()).getQuantity();
-
   if (Desc->isArray())
     return ASTCtx.getTypeSizeInChars(Desc->getElemQualType()).getQuantity() *
            Desc->getNumElems();
+  if (Desc->isRecord()) {
+    // Can't use Descriptor::getType() as that may return a pointer type. Look
+    // at the decl directly.
+    return ASTCtx
+        .getTypeSizeInChars(
+            ASTCtx.getCanonicalTagType(Desc->ElemRecord->getDecl()))
+        .getQuantity();
+  }
 
-  if (Desc->isRecord())
-    return ASTCtx.getTypeSizeInChars(Desc->getType()).getQuantity();
-
-  llvm_unreachable("Unhandled descriptor type");
-  return 0;
+  return std::nullopt;
 }
 
+/// Compute the byte offset of \p Ptr in the full declaration.
 static unsigned computePointerOffset(const ASTContext &ASTCtx,
                                      const Pointer &Ptr) {
   unsigned Result = 0;
 
   Pointer P = Ptr;
-  while (P.isArrayElement() || P.isField()) {
+  while (P.isField() || P.isArrayElement()) {
----------------
tbaederr wrote:

No, the previous order just caused some assertion failures in `isArrayElement` IIRC. This version works for more cases.

https://github.com/llvm/llvm-project/pull/153601