Rework interface for bitset-using features to use a notion of LTO visibility.

Bitsets, and the compiler features they rely on (vtable opt, CFI),
only have visibility within the LTO'd part of the linkage unit. Therefore,
only enable these features for classes with hidden LTO visibility. This
notion is based on object file visibility or (on Windows)
dllimport/dllexport attributes.

We provide the [[clang::lto_visibility_public]] attribute to override the
compiler's LTO visibility inference in cases where the class is defined
in the non-LTO'd part of the linkage unit, or where the ABI supports
calling classes derived from abstract base classes with hidden visibility
in other linkage units (e.g. COM on Windows).

If the cross-DSO CFI mode is enabled, bitset checks are emitted even for
classes with public LTO visibility, as that mode uses a separate mechanism
to cause bitsets to be exported.

This mechanism replaces the whole-program-vtables blacklist, so remove the
-fwhole-program-vtables-blacklist flag.

Because __declspec(uuid()) now implies [[clang::lto_visibility_public]], the
support for the special attr:uuid blacklist entry is removed.

Differential Revision: http://reviews.llvm.org/D18635

llvm-svn: 267784

1 files changed, 4 insertions, 8 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 34d1111889a..a75e4aa2a32 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -490,8 +490,6 @@ private:
   /// MDNodes.
   llvm::DenseMap<QualType, llvm::Metadata *> MetadataIdMap;
 
-  SanitizerBlacklist WholeProgramVTablesBlacklist;
-
 public:
   CodeGenModule(ASTContext &C, const HeaderSearchOptions &headersearchopts,
                 const PreprocessorOptions &ppopts,
@@ -1115,12 +1113,10 @@ public:
   void EmitOMPDeclareReduction(const OMPDeclareReductionDecl *D,
                                CodeGenFunction *CGF = nullptr);
 
-  /// Returns whether we need bit sets attached to vtables.
-  bool NeedVTableBitSets();
-
-  /// Returns whether the given record is blacklisted from whole-program
-  /// transformations (i.e. CFI or whole-program vtable optimization).
-  bool IsBitSetBlacklistedRecord(const CXXRecordDecl *RD);
+  /// Returns whether the given record has hidden LTO visibility and therefore
+  /// may participate in (single-module) CFI and whole-program vtable
+  /// optimization.
+  bool HasHiddenLTOVisibility(const CXXRecordDecl *RD);
 
   /// Emit bit set entries for the given vtable using the given layout if
   /// vptr CFI is enabled.