[CFI] Add CFI-icall pointer type generalization

Summary:
This change allows generalizing pointers in type signatures used for
cfi-icall by enabling the -fsanitize-cfi-icall-generalize-pointers flag.
This works by 1) emitting an additional generalized type signature
metadata node for functions and 2) llvm.type.test()ing for the
generalized type for translation units with the flag specified.

This flag is incompatible with -fsanitize-cfi-cross-dso because it would
require emitting twice as many type hashes which would increase artifact
size.

Reviewers: pcc, eugenis

Reviewed By: pcc

Subscribers: kcc

Differential Revision: https://reviews.llvm.org/D39358

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@317044 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/CodeGen/CodeGenModule.h b/lib/CodeGen/CodeGenModule.h
index 21bab6cfa0..7a47c576c0 100644
--- a/lib/CodeGen/CodeGenModule.h
+++ b/lib/CodeGen/CodeGenModule.h
@@ -497,7 +497,9 @@ private:
   /// Mapping from canonical types to their metadata identifiers. We need to
   /// maintain this mapping because identifiers may be formed from distinct
   /// MDNodes.
-  llvm::DenseMap<QualType, llvm::Metadata *> MetadataIdMap;
+  typedef llvm::DenseMap<QualType, llvm::Metadata *> MetadataTypeMap;
+  MetadataTypeMap MetadataIdMap;
+  MetadataTypeMap GeneralizedMetadataIdMap;
 
 public:
   CodeGenModule(ASTContext &C, const HeaderSearchOptions &headersearchopts,
@@ -1209,6 +1211,11 @@ public:
   /// internal identifiers).
   llvm::Metadata *CreateMetadataIdentifierForType(QualType T);
 
+  /// Create a metadata identifier for the generalization of the given type.
+  /// This may either be an MDString (for external identifiers) or a distinct
+  /// unnamed MDNode (for internal identifiers).
+  llvm::Metadata *CreateMetadataIdentifierGeneralized(QualType T);
+
   /// Create and attach type metadata to the given function.
   void CreateFunctionTypeMetadata(const FunctionDecl *FD, llvm::Function *F);