[clang] [ARM] Empty structs are 1-byte for C++ ABI (PR #124762)

[Eli Friedman via cfe-commits]

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@@ -752,10 +780,13 @@ RValue ARMABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
   CharUnits SlotSize = CharUnits::fromQuantity(4);
 
   // Empty records are ignored for parameter passing purposes.
-  if (isEmptyRecord(getContext(), Ty, true))
+  uint64_t Size = getContext().getTypeSize(Ty);
+  bool IsEmpty = isEmptyRecord(getContext(), Ty, true);
+  if ((IsEmpty || Size == 0) && shouldIgnoreEmptyArg(Ty))
     return Slot.asRValue();
 
-  CharUnits TySize = getContext().getTypeSizeInChars(Ty);
+  CharUnits TySize =
+      std::max(getContext().getTypeSizeInChars(Ty), CharUnits::fromQuantity(1));
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efriedma-quic wrote:

If we get here, we know the size isn't zero, I think?

https://github.com/llvm/llvm-project/pull/124762