[clang] Implement [[msvc::no_unique_address]] (PR #65675)

[Amy Huang via cfe-commits]

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@@ -55,7 +55,7 @@ CXX11(unlikely)
 // CHECK: likely: 201803L
 // CHECK: maybe_unused: 201603L
 // ITANIUM: no_unique_address: 201803L
-// WINDOWS: no_unique_address: 0
+// WINDOWS: no_unique_address: 201803L 
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amykhuang wrote:

Tried this and the inheritance part wasn't quite working (think that the NoUniqueAddress should be a class, but in that case, not sure how to parse the two attributes). I did a slightly different version where we have three attributes with no inheritance (MS, Itanium, and general) and just parse the MS and Itanium versions as the general version in SemaDeclAttr. It at least passes the tests that were broken before.

https://github.com/llvm/llvm-project/pull/65675