[clang] [Clang][Windows] Preserve x86_fp80 and vector alignment under #pragma pack. (PR #208256)

[Zahira Ammarguellat via cfe-commits]

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@@ -2539,9 +2548,22 @@ TypeInfo ASTContext::getTypeInfoImpl(const Type *T) const {
     const ASTRecordLayout &Layout = getASTRecordLayout(RD);
     Width = toBits(Layout.getSize());
     Align = toBits(Layout.getAlignment());
-    AlignRequirement = RD->hasAttr<AlignedAttr>()
-                           ? AlignRequirementKind::RequiredByRecord
-                           : AlignRequirementKind::None;
+    // Check if the record has an aligned attribute, or if it contains
+    // fields with ABI-required alignment (e.g., x86_fp80).
+    if (RD->hasAttr<AlignedAttr>()) {
+      AlignRequirement = AlignRequirementKind::RequiredByRecord;
+    } else {
+      // Check if any field has RequiredByABI alignment requirement.
+      // If so, propagate it to the record.
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zahiraam wrote:

Testing shows this isn't the case for nested structs under `#pragma pack`. I added a test in the LIT test to show that. The test cases demonstrate that both explicit (`alignas`) and implicit `(x86_fp80`)    alignment requirements need this propagation to work correctly through nesting.

https://github.com/llvm/llvm-project/pull/208256