[clang] [ARM, AArch64] Fix passing of structures with aligned base classes (PR #135564)

[John McCall via cfe-commits]

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@@ -1302,6 +1302,7 @@ ItaniumRecordLayoutBuilder::LayoutBase(const BaseSubobjectInfo *Base) {
     setSize(std::max(getSize(), Offset + Layout.getSize()));
 
   // Remember max struct/class alignment.
+  UnadjustedAlignment = std::max(UnadjustedAlignment, PreferredBaseAlign);
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rjmccall wrote:

Not too surprising, I hope. I have to confess that Apple used to have a similar statement in our x86_64 ABI documentation until one of our divergences was pointed out (by someone from Microsoft, coincidentally), at which point we rolled up our sleeves and [documented the rest of them](https://developer.apple.com/documentation/xcode/writing-64-bit-intel-code-for-apple-platforms).

https://github.com/llvm/llvm-project/pull/135564