[llvm] [clang] [clang, SystemZ] Pass HasDef flag to getMinGlobalAlign(). (PR #73511)

[Jonas Paulsson via cfe-commits]

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@@ -1687,7 +1687,8 @@ CharUnits ASTContext::getDeclAlign(const Decl *D, bool ForAlignof) const {
       if (VD->hasGlobalStorage() && !ForAlignof) {
         uint64_t TypeSize =
             !BaseT->isIncompleteType() ? getTypeSize(T.getTypePtr()) : 0;
-        Align = std::max(Align, getTargetInfo().getMinGlobalAlign(TypeSize));
+        Align = std::max(Align, getTargetInfo().getMinGlobalAlign(
+                                    TypeSize, VD->hasDefinition()));
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JonPsson1 wrote:

Good point!

It seems to me though that this is something the backend must handle. Even with this patch, e.g. a weak 4-byte integer would get the natural alignment, and could later be replaced with an unaligned 4-byte integer by the linker. This patch only removes the ABI minimal alignment, i.e. the requirement to align everything by at least 2 bytes.

A recent GCC does not handle this either: it emits a LARL for a weak int. Could it be that the linker preserves the alignment of the original (weak) object?


https://github.com/llvm/llvm-project/pull/73511