Restore previous structure ABI behavior for bit-fields with the packed attribute for PS4 targets.

An ABI change was introduced in r254596 that modified structure layouts when the 'packed' attribute was used on one-byte bitfields. Since the PS4 target needs to maintain backwards compatibility for all structure layouts, this change reintroduces the old behavior for PS4 targets only. It also introduces PS4 specific cases to the relevant test.

Patch by Matthew Voss.

llvm-svn: 310388

1 files changed, 21 insertions, 7 deletions

diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 6e29717643b..cef84116db3 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -1304,14 +1304,28 @@ static void handlePackedAttr(Sema &S, Decl *D, const AttributeList &Attr) {
     TD->addAttr(::new (S.Context) PackedAttr(Attr.getRange(), S.Context,
                                         Attr.getAttributeSpellingListIndex()));
   else if (FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
-    // Report warning about changed offset in the newer compiler versions.
-    if (!FD->getType()->isDependentType() &&
-        !FD->getType()->isIncompleteType() && FD->isBitField() &&
-        S.Context.getTypeAlign(FD->getType()) <= 8)
-      S.Diag(Attr.getLoc(), diag::warn_attribute_packed_for_bitfield);
+    bool BitfieldByteAligned = (!FD->getType()->isDependentType() &&
+                                !FD->getType()->isIncompleteType() &&
+                                FD->isBitField() &&
+                                S.Context.getTypeAlign(FD->getType()) <= 8);
+
+    if (S.getASTContext().getTargetInfo().getTriple().isPS4()) {
+      if (BitfieldByteAligned)
+        // The PS4 target needs to maintain ABI backwards compatibility.
+        S.Diag(Attr.getLoc(), diag::warn_attribute_ignored_for_field_of_type)
+          << Attr.getName() << FD->getType();
+      else
+        FD->addAttr(::new (S.Context) PackedAttr(
+                    Attr.getRange(), S.Context, Attr.getAttributeSpellingListIndex()));
+    } else {
+      // Report warning about changed offset in the newer compiler versions.
+      if (BitfieldByteAligned)
+        S.Diag(Attr.getLoc(), diag::warn_attribute_packed_for_bitfield);
+
+      FD->addAttr(::new (S.Context) PackedAttr(
+                  Attr.getRange(), S.Context, Attr.getAttributeSpellingListIndex()));
+    }
 
-    FD->addAttr(::new (S.Context) PackedAttr(
-        Attr.getRange(), S.Context, Attr.getAttributeSpellingListIndex()));
   } else
     S.Diag(Attr.getLoc(), diag::warn_attribute_ignored) << Attr.getName();
 }