[clang] [clang][NFC] Specify Type and ExtQuals as having 16-byte alignment (PR #68377)

[Vlad Serebrennikov via cfe-commits]

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@@ -1982,9 +1986,9 @@ class alignas(8) Type : public ExtQualsTypeCommonBase {
   Type(TypeClass tc, QualType canon, TypeDependence Dependence)
       : ExtQualsTypeCommonBase(this,
                                canon.isNull() ? QualType(this_(), 0) : canon) {
-    static_assert(sizeof(*this) <= 8 + sizeof(ExtQualsTypeCommonBase),
+    static_assert(sizeof(*this) <= 16 + sizeof(ExtQualsTypeCommonBase),
                   "changing bitfields changed sizeof(Type)!");
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Endilll wrote:

This check has been broken, because `sizeof` didn't take into the account that `Type` objects are actually laid out in memory on 16-byte boundary, which results in 24 bytes of data and 8 bytes of padding. My change just affirms the status quo that Type is indeed takes 16 bytes more memory than `ExtQuals`, which has size 16.

https://github.com/llvm/llvm-project/pull/68377