Extract a TBAAVerifier out of the verifier (NFC)

This is intended to be used (in a later patch) by the BitcodeReader
to detect invalid TBAA and drop them when loading bitcode, so that
we don't break client that have legacy bitcode with possible invalid
TBAA.

Differential Revision: https://reviews.llvm.org/D27838

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289927 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/Verifier.h

@@ -23,6 +23,10 @@
 
 #include "llvm/IR/PassManager.h"
 
+namespace {
+struct VerifierSupport;
+}
+
 namespace llvm {
 
 class Function;
@@ -31,6 +35,41 @@ class ModulePass;
 class Module;
 class raw_ostream;
 
+/// Verify that the TBAA Metadatas are valid.
+class TBAAVerifier {
+  VerifierSupport *Diagnostic = nullptr;
+
+  /// Helper to diagnose a failure
+  template <typename... Tys> void CheckFailed(Tys &&... Args);
+
+  /// Cache of TBAA base nodes that have already been visited.  This cachce maps
+  /// a node that has been visited to a pair (IsInvalid, BitWidth) where
+  ///
+  ///  \c IsInvalid is true iff the node is invalid.
+  ///  \c BitWidth, if non-zero, is the bitwidth of the integer used to denoting
+  ///    the offset of the access.  If zero, only a zero offset is allowed.
+  ///
+  /// \c BitWidth has no meaning if \c IsInvalid is true.
+  typedef std::pair<bool, unsigned> TBAABaseNodeSummary;
+  DenseMap<MDNode *, TBAABaseNodeSummary> TBAABaseNodes;
+
+  /// \name Helper functions used by \c visitTBAAMetadata.
+  /// @{
+  MDNode *getFieldNodeFromTBAABaseNode(Instruction &I, MDNode *BaseNode,
+                                       APInt &Offset);
+  TBAAVerifier::TBAABaseNodeSummary verifyTBAABaseNode(Instruction &I,
+                                                       MDNode *BaseNode);
+  TBAABaseNodeSummary verifyTBAABaseNodeImpl(Instruction &I, MDNode *BaseNode);
+  /// @}
+
+public:
+  TBAAVerifier(VerifierSupport *Diagnostic = nullptr)
+      : Diagnostic(Diagnostic) {}
+  // Visit an instruction and return true if it is valid, return false it an
+  // invalid TBAA is attached.
+  bool visitTBAAMetadata(Instruction &I, MDNode *MD);
+};
+
 /// \brief Check a function for errors, useful for use when debugging a
 /// pass.
 ///