[clang] [clang][PAC] Support trivially_relocating polymorphic objects (PR #144420)

[Oliver Hunt via cfe-commits]

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@@ -1727,6 +1727,11 @@ ASTContext::PointerAuthContent ASTContext::findPointerAuthContent(QualType T) {
   T = T.getCanonicalType();
   if (T.hasAddressDiscriminatedPointerAuth())
     return PointerAuthContent::AddressDiscriminatedData;
+
+  T = getBaseElementType(T).getCanonicalType();
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ojhunt wrote:

Adding this simplifies the logic in codegen, and to an extent removes a footgun in the form of not requiring every caller to lower the type to the base element prior to calling.

https://github.com/llvm/llvm-project/pull/144420